rfc9690.original   rfc9690.txt 
Limited Additional Mechanisms for PKIX and SMIME R. Housley Internet Engineering Task Force (IETF) R. Housley
Internet-Draft Vigil Security Request for Comments: 9690 Vigil Security
Obsoletes: 5990 (if approved) S. Turner Obsoletes: 5990 S. Turner
Intended status: Standards Track sn3rd Category: Standards Track sn3rd
Expires: 7 December 2024 5 June 2024 ISSN: 2070-1721 February 2025
Use of the RSA-KEM Algorithm in the Cryptographic Message Syntax (CMS) Use of the RSA-KEM Algorithm in the Cryptographic Message Syntax (CMS)
draft-ietf-lamps-rfc5990bis-08
Abstract Abstract
The RSA Key Encapsulation Mechanism (RSA-KEM) Algorithm is a one-pass The RSA Key Encapsulation Mechanism (RSA-KEM) algorithm is a one-pass
(store-and-forward) cryptographic mechanism for an originator to (store-and-forward) cryptographic mechanism for an originator to
securely send keying material to a recipient using the recipient's securely send keying material to a recipient using the recipient's
RSA public key. The RSA-KEM Algorithm is specified in Clause 11.5 of RSA public key. The RSA-KEM algorithm is specified in Clause 11.5 of
ISO/IEC: 18033-2:2006. This document specifies the conventions for ISO/IEC: 18033-2:2006. This document specifies the conventions for
using the RSA-KEM Algorithm as a standalone KEM algorithm and the using the RSA-KEM algorithm as a standalone KEM algorithm and the
conventions for using the RSA-KEM Algorithm with the Cryptographic conventions for using the RSA-KEM algorithm with the Cryptographic
Message Syntax (CMS) using KEMRecipientInfo as specified in RFC XXXX. Message Syntax (CMS) using KEMRecipientInfo as specified in RFC 9629.
This document obsoletes RFC 5990. This document obsoletes RFC 5990.
RFC EDITOR: Please replace XXXX with the RFC number assigned to
draft-ietf-lamps-cms-kemri.
About This Document
This note is to be removed before publishing as an RFC.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
1.1. RSA-KEM Algorithm Rationale . . . . . . . . . . . . . . . 3 1.1. RSA-KEM Algorithm Rationale
1.2. RSA-KEM Algorithm Summary . . . . . . . . . . . . . . . . 4 1.2. RSA-KEM Algorithm Summary
1.3. CMS KEMRecipientInfo Processing Summary . . . . . . . . . 5 1.3. CMS KEMRecipientInfo Processing Summary
1.4. Conventions and Definitions . . . . . . . . . . . . . . . 6 1.4. Conventions and Definitions
1.5. ASN.1 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.5. ASN.1
1.6. Changes Since RFC 5990 . . . . . . . . . . . . . . . . . 6 1.6. Changes Since RFC 5990
2. Use of the RSA-KEM Algorithm in CMS . . . . . . . . . . . . . 7 2. Use of the RSA-KEM Algorithm in CMS
2.1. Mandatory To Implement . . . . . . . . . . . . . . . . . 7 2.1. Mandatory To Implement
2.2. RecipientInfo Conventions . . . . . . . . . . . . . . . . 8 2.2. RecipientInfo Conventions
2.3. Certificate Conventions . . . . . . . . . . . . . . . . . 8 2.3. Certificate Conventions
2.4. SMIMECapabilities Attribute Conventions . . . . . . . . . 10 2.4. SMIMECapabilities Attribute Conventions
3. Security Considerations . . . . . . . . . . . . . . . . . . . 11 3. Security Considerations
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 4. IANA Considerations
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 5. References
5.1. Normative References . . . . . . . . . . . . . . . . . . 13 5.1. Normative References
5.2. Informative References . . . . . . . . . . . . . . . . . 15 5.2. Informative References
Appendix A. RSA-KEM Algorithm . . . . . . . . . . . . . . . . . 16 Appendix A. RSA-KEM Algorithm
A.1. Originator's Operations: RSA-KEM Encapsulate() . . . . . 16 A.1. Originator's Operations: RSA-KEM Encapsulate()
A.2. Recipient's Operations: RSA-KEM Decapsulate() . . . . . . 17 A.2. Recipient's Operations: RSA-KEM Decapsulate()
Appendix B. ASN.1 Syntax . . . . . . . . . . . . . . . . . . . . 18 Appendix B. ASN.1 Syntax
B.1. Underlying Components . . . . . . . . . . . . . . . . . . 18 B.1. Underlying Components
B.2. ASN.1 Module . . . . . . . . . . . . . . . . . . . . . . 20 B.2. ASN.1 Module
Appendix C. SMIMECapabilities Examples . . . . . . . . . . . . . 24 Appendix C. SMIMECapabilities Examples
Appendix D. RSA-KEM CMS Enveloped-Data Example . . . . . . . . . 26 Appendix D. RSA-KEM CMS Enveloped-Data Example
D.1. Originator RSA-KEM Encapsulate() Processing . . . . . . . 26 D.1. Originator RSA-KEM Encapsulate() Processing
D.2. Originator CMS Processing . . . . . . . . . . . . . . . . 27 D.2. Originator CMS Processing
D.3. Recipient RSA-KEM Decapsulate() Processing . . . . . . . 30 D.3. Recipient RSA-KEM Decapsulate() Processing
D.4. Recipient CMS Processing . . . . . . . . . . . . . . . . 32 D.4. Recipient CMS Processing
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 33 Acknowledgements
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 Authors' Addresses
1. Introduction 1. Introduction
The RSA Key Encapsulation Mechanism (RSA-KEM) Algorithm is a one-pass The RSA Key Encapsulation Mechanism (RSA-KEM) algorithm is a one-pass
(store-and-forward) cryptographic mechanism for an originator to (store-and-forward) cryptographic mechanism for an originator to
securely send keying material to a recipient using the recipient's securely send keying material to a recipient using the recipient's
RSA public key. The RSA-KEM Algorithm is specified in Clause 11.5 of RSA public key. The RSA-KEM algorithm is specified in Clause 11.5 of
[ISO18033-2]. [ISO18033-2].
The RSA-KEM Algorithm takes a different approach than other RSA key The RSA-KEM algorithm takes a different approach than other RSA key
transport mechanisms [RFC8017], with the goal of providing higher transport mechanisms [RFC8017] with the goal of providing higher
security assurance while also satisfying the KEM interface. The RSA- security assurance while also satisfying the KEM interface. The RSA-
KEM Algorithm encrypts a random integer with the recipient's RSA KEM algorithm encrypts a random integer with the recipient's RSA
public key, and derives a shared secret from the random integer. The public key and derives a shared secret from the random integer. The
originator and recipient can derive a symmetric key from the shared originator and recipient can derive a symmetric key from the shared
secret. For example, a key-encryption key can be derived from the secret. For example, a key-encryption key (KEK) can be derived from
shared secret to wrap a content-encryption key. the shared secret to wrap a content-encryption key (CEK).
In the Cryptographic Message Syntax (CMS) [RFC5652] using In the Cryptographic Message Syntax (CMS) [RFC5652] using
KEMRecipientInfo [I-D.ietf-lamps-cms-kemri], the shared secret value KEMRecipientInfo [RFC9629], the shared-secret value is input to a key
is input to a key-derivation function to compute a key-encryption derivation function (KDF) to compute a key-encryption key and wrap a
key, and wrap a symmetric content-encryption key with the key- symmetric content-encryption key with the key-encryption key. In
encryption key. In this way, the originator and the recipient end up this way, the originator and the recipient end up with the same
with the same content-encryption key. content-encryption key.
For completeness, a specification of the RSA-KEM Algorithm is given For completeness, a specification of the RSA-KEM algorithm is given
in Appendix A of this document; ASN.1 syntax is given in Appendix B. in Appendix A of this document. ASN.1 syntax is given in Appendix B.
1.1. RSA-KEM Algorithm Rationale 1.1. RSA-KEM Algorithm Rationale
The RSA-KEM Algorithm provides higher security assurance than other The RSA-KEM algorithm provides higher security assurance than other
variants of the RSA cryptosystem for two reasons. First, the input variants of the RSA cryptosystem for two reasons. First, the input
to the underlying RSA operation is a string-encoded random integer to the underlying RSA operation is a string-encoded random integer
between 0 and n-1, where n is the RSA modulus, so it does not have between 0 and n-1, where n is the RSA modulus, so it does not have
any structure that could be exploited by an adversary. Second, the any structure that could be exploited by an adversary. Second, the
input is independent of the keying material so the result of the RSA input is independent of the keying material, so the result of the RSA
decryption operation is not directly available to an adversary. As a decryption operation is not directly available to an adversary. As a
result, the RSA-KEM Algorithm enjoys a "tight" security proof in the result, the RSA-KEM algorithm enjoys a "tight" security proof in the
random oracle model. (In other padding schemes, such as PKCS #1 v1.5 random oracle model. (In other padding schemes, such as PKCS #1 v1.5
[RFC8017], the input has structure and/or depends on the keying [RFC8017], the input has structure and depends on the keying
material, and the provable security assurances are not as strong.) material. Additionally, the provable security assurances are not as
strong.)
The approach is also architecturally convenient because the public- The approach is also architecturally convenient because the public-
key operations are separate from the symmetric operations on the key operations are separate from the symmetric operations on the
keying material. Another benefit is that the length of the keying keying material. Another benefit is that the length of the keying
material is determined by the symmetric algorithms, not the size of material is determined by the symmetric algorithms, not the size of
the RSA modulus. the RSA modulus.
1.2. RSA-KEM Algorithm Summary 1.2. RSA-KEM Algorithm Summary
All KEM algorithms provide three functions: KeyGen(), Encapsulate(), All KEM algorithms provide three functions: KeyGen(), Encapsulate(),
and Decapsulate(). and Decapsulate().
The following summarizes these three functions for RSA-KEM: The following summarizes these three functions for the RSA-KEM
algorithm:
KeyGen() -> (pk, sk): KeyGen() -> (pk, sk):
Generate the public key (pk) and a private key (sk) as described Generate the public key (pk) and a private key (sk) as described
in Section 3 of [RFC8017]. in Section 3 of [RFC8017].
Encapsulate(pk) -> (ct, SS): Encapsulate(pk) -> (ct, SS):
Given the recipient's public key (pk), produce a ciphertext (ct) Given the recipient's public key (pk), produce a ciphertext (ct)
to be passed to the recipient and a shared secret (SS) for use by to be passed to the recipient and a shared secret (SS) for use by
the originator, as follows: the originator as follows:
1. Generate a random integer z between 0 and n-1. 1. Generate a random integer z between 0 and n-1.
2. Encrypt the integer z with the recipient's RSA public key to 2. Encrypt the integer z with the recipient's RSA public key to
obtain the ciphertext: obtain the ciphertext:
ct = z^e mod n ct = z^e mod n
3. Derive a shared secret from the integer z using a Key 3. Derive a shared secret from the integer z using a Key
Derivation Function (KDF): Derivation Function (KDF):
SS = KDF(Z, ssLen) SS = KDF(Z, ssLen)
4. The ciphertext and the shared secret are returned by the 4. The ciphertext and the shared secret are returned by the
function. The originator sends the ciphertext to the recipient. function. The originator sends the ciphertext to the
recipient.
Decapsulate(sk, ct) -> SS: Decapsulate(sk, ct) -> SS:
Given the private key (sk) and the ciphertext (ct), produce the Given the private key (sk) and the ciphertext (ct), produce the
shared secret (SS) for the recipient as follows: shared secret (SS) for the recipient as follows:
1. Decrypt the ciphertext with the recipient's RSA private key to 1. Decrypt the ciphertext with the recipient's RSA private key to
obtain the random integer z: obtain the random integer z:
z = ct^d mod n z = ct^d mod n
2. Derive a shared secret from the integer z: 2. Derive a shared secret from the integer z:
SS = KDF(Z, ssLen) SS = KDF(Z, ssLen)
3. The shared secret is returned by the function. 3. The shared secret is returned by the function.
1.3. CMS KEMRecipientInfo Processing Summary 1.3. CMS KEMRecipientInfo Processing Summary
To support the RSA-KEM algorithm, the CMS originator MUST implement To support the RSA-KEM algorithm, the CMS originator MUST implement
Encapsulate(). Encapsulate().
Given a content-encryption key CEK, the RSA-KEM Algorithm processing Given a content-encryption key CEK, the RSA-KEM algorithm processing
by the originator to produce the values that are carried in the CMS by the originator to produce the values that are carried in the CMS
KEMRecipientInfo can be summarized as: KEMRecipientInfo can be summarized as follows:
1. Obtain the shared secret using the Encapsulate() function of 1. Obtain the shared secret using the Encapsulate() function of the
the RSA-KEM algorithm and the recipient's RSA public key: RSA-KEM algorithm and the recipient's RSA public key:
(ct, SS) = Encapsulate(pk) (ct, SS) = Encapsulate(pk)
2. Derive a key-encryption key KEK from the shared secret: 2. Derive a key-encryption key KEK from the shared secret:
KEK = KDF(SS, kekLength, otherInfo) KEK = KDF(SS, kekLength, otherInfo)
3. Wrap the CEK with the KEK to obtain wrapped keying material 3. Wrap the CEK with the KEK to obtain wrapped keying material WK:
WK:
WK = WRAP(KEK, CEK) WK = WRAP(KEK, CEK)
4. The originator sends the ciphertext and WK to the recipient in 4. The originator sends the ciphertext and WK to the recipient in
the CMS KEMRecipientInfo structure. the CMS KEMRecipientInfo structure.
To support the RSA-KEM algorithm, the CMS recipient MUST implement To support the RSA-KEM algorithm, the CMS recipient MUST implement
Decapsulate(). Decapsulate().
The RSA-KEM algorithm recipient processing of the values obtained The RSA-KEM algorithm recipient processing of the values obtained
from the KEMRecipientInfo structure can be summarized as: from the KEMRecipientInfo structure is summarized as follows:
1. Obtain the shared secret using the Decapsulate() function of 1. Obtain the shared secret using the Decapsulate() function of the
the RSA-KEM algorithm and the recipient's RSA private key: RSA-KEM algorithm and the recipient's RSA private key:
SS = Decapsulate(sk, ct) SS = Decapsulate(sk, ct)
2. Derive a key-encryption key KEK from the shared secret: 2. Derive a key-encryption key KEK from the shared secret:
KEK = KDF(SS, kekLength, otherInfo) KEK = KDF(SS, kekLength, otherInfo)
3. Unwrap the WK with the KEK to obtain content-encryption key 3. Unwrap the WK with the KEK to obtain the content-encryption key
CEK: CEK:
CEK = UNWRAP(KEK, WK) CEK = UNWRAP(KEK, WK)
Note that the KDF used to process the KEMRecipientInfo structure MAY Note that the KDF used to process the KEMRecipientInfo structure MAY
be different from the KDF used to derive the shared secret in the be different from the KDF used to derive the shared secret in the
RSA-KEM algorithm. RSA-KEM algorithm.
1.4. Conventions and Definitions 1.4. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
skipping to change at page 6, line 31 skipping to change at line 247
1.5. ASN.1 1.5. ASN.1
CMS values are generated using ASN.1 [X.680], which uses the Basic CMS values are generated using ASN.1 [X.680], which uses the Basic
Encoding Rules (BER) and the Distinguished Encoding Rules (DER) Encoding Rules (BER) and the Distinguished Encoding Rules (DER)
[X.690]. [X.690].
1.6. Changes Since RFC 5990 1.6. Changes Since RFC 5990
RFC 5990 [RFC5990] specified the conventions for using the RSA-KEM RFC 5990 [RFC5990] specified the conventions for using the RSA-KEM
Algorithm in CMS as a key transport algorithm. That is, it used algorithm in CMS as a key transport algorithm. That is, it used
KeyTransRecipientInfo [RFC5652] for each recipient. Since the KeyTransRecipientInfo [RFC5652] for each recipient. Since the
publication of RFC 5990, a new KEMRecipientInfo structure publication of RFC 5990, a new KEMRecipientInfo structure [RFC9629]
[I-D.ietf-lamps-cms-kemri] has been defined to support KEM has been defined to support KEM algorithms. When the id-rsa-kem
algorithms. When the id-rsa-kem algorithm identifier appears in the algorithm identifier appears in the SubjectPublicKeyInfo field of a
SubjectPublicKeyInfo field of a certificate, the complex parameter certificate, the complex parameter structure defined in RFC 5990 can
structure defined in RFC 5990 can be omitted; however, the parameters be omitted; however, the parameters are allowed for backward
are allowed for backward compatibility. Also, to avoid visual compatibility. Also, to avoid visual confusion with id-kem-rsa,
confusion with id-kem-rsa, id-rsa-kem-spki is introduced as an alias id-rsa-kem-spki is introduced as an alias for id-rsa-kem.
for id-rsa-kem.
RFC 5990 used EK as the EncryptedKey, which is the concatenation of RFC 5990 used EK as the EncryptedKey, which is the concatenation of
the ciphertext C and the wrapped key WK, EK = (C || WK). The use of the ciphertext C and the wrapped key WK, EK = (C || WK). The use of
EK was necessary to align with the KeyTransRecipientInfo structure. EK was necessary to align with the KeyTransRecipientInfo structure.
In this document, the ciphertext and the wrapped key are sent in In this document, the ciphertext and the wrapped key are sent in
separate fields of the KEMRecipientInfo structure. In particular, separate fields of the KEMRecipientInfo structure. In particular,
the ciphertext is carried in the kemct field, and wrapped key is the ciphertext is carried in the kemct field, and the wrapped key is
carried in the encryptedKey field. See Appendix A for details about carried in the encryptedKey field. See Appendix A for details about
the computation of the ciphertext. the computation of the ciphertext.
RFC 5990 included support for Camellia and Triple-DES block ciphers; RFC 5990 included support for Camellia and Triple-DES block ciphers;
discussion of these block ciphers is removed from this document, but discussion of these block ciphers does not appear in this document,
the algorithm identifiers remain in the ASN.1 Module Appendix B.2. but the algorithm identifiers remain in the ASN.1 module (see
Appendix B.2).
RFC 5990 included support for SHA-1 hash function; discussion of this RFC 5990 included support for SHA-1 hash function; discussion of this
hash function is removed from this document, but the algorithm hash function does not appear this document, but the algorithm
identifier remains in the ASN.1 module Appendix B.2. identifier remains in the ASN.1 module (see Appendix B.2).
RFC 5990 required support for the KDF3 key-derivation function RFC 5990 required support for the KDF3 key derivation function
[ANS-X9.44]; this document continues to require support for the KDF3 [ANS-X9.44]; this document continues to require support for the KDF3
key-derivation function, but it requires support for SHA-256 [SHS] as key derivation function, but it requires support for SHA-256 [SHS] as
the hash function. the hash function.
RFC 5990 recommended support for alternatives to KDF3 and AES-Wrap- RFC 5990 recommended support for alternatives to KDF3 and AES-Wrap-
128; this document simply states that other key-derivation functions 128; this document simply states that other key derivation functions
and other key-encryption algorithms MAY be supported. and other key-encryption algorithms MAY be supported.
RFC 5990 supported the future definition of additional KEM algorithms RFC 5990 supported the future definition of additional KEM algorithms
that use RSA; this document supports only one, and it is identified that use RSA; this document supports only one, and it is identified
by the id-kem-rsa object identifier. by the id-kem-rsa object identifier.
RFC 5990 included an ASN.1 module; this document provides an RFC 5990 included an ASN.1 module; this document provides an
alternative ASN.1 module that follows the conventions established in alternative ASN.1 module that follows the conventions established in
[RFC5911], [RFC5912], and [RFC6268]. The new ASN.1 module [RFC5911], [RFC5912], and [RFC6268]. The new ASN.1 module
Appendix B.2 produces the same bits-on-the-wire as the one in RFC (Appendix B.2) produces the same bits-on-the-wire as the one in RFC
5990. 5990.
2. Use of the RSA-KEM Algorithm in CMS 2. Use of the RSA-KEM Algorithm in CMS
The RSA-KEM Algorithm MAY be employed for one or more recipients in The RSA-KEM algorithm MAY be employed for one or more recipients in
the CMS enveloped-data content type [RFC5652], the CMS authenticated- the CMS enveloped-data content type [RFC5652], the CMS authenticated-
data content type [RFC5652], or the CMS authenticated-enveloped-data data content type [RFC5652], or the CMS authenticated-enveloped-data
content type [RFC5083]. In each case, the KEMRecipientInfo content type [RFC5083]. In each case, the KEMRecipientInfo [RFC9629]
[I-D.ietf-lamps-cms-kemri] is used with the RSA-KEM Algorithm to is used with the RSA-KEM algorithm to securely transfer the content-
securely transfer the content-encryption key from the originator to encryption key from the originator to the recipient.
the recipient.
2.1. Mandatory To Implement 2.1. Mandatory To Implement
A CMS implementation that supports the RSA-KEM Algorithm MUST support A CMS implementation that supports the RSA-KEM algorithm MUST support
at least the following underlying components: at least the following underlying components:
* For the key-derivation function, an implementation MUST support * For the key derivation function, an implementation MUST support
KDF3 [ANS-X9.44] with SHA-256 [SHS]. KDF3 [ANS-X9.44] with SHA-256 [SHS].
* For key-wrapping, an implementation MUST support the AES-Wrap-128 * For key-wrapping, an implementation MUST support the AES-Wrap-128
[RFC3394] key-encryption algorithm. [RFC3394] key-encryption algorithm.
An implementation MAY also support other key-derivation functions and An implementation MAY also support other key derivation functions and
other key-encryption algorithms as well. other key-encryption algorithms.
2.2. RecipientInfo Conventions 2.2. RecipientInfo Conventions
When the RSA-KEM Algorithm is employed for a recipient, the When the RSA-KEM algorithm is employed for a recipient, the
RecipientInfo alternative for that recipient MUST be RecipientInfo alternative for that recipient MUST be
OtherRecipientInfo using the KEMRecipientInfo structure OtherRecipientInfo using the KEMRecipientInfo structure [RFC9629].
[I-D.ietf-lamps-cms-kemri]. The fields of the KEMRecipientInfo MUST The fields of the KEMRecipientInfo MUST have the following values:
have the following values:
version is the syntax version number; it MUST be 0. * version is the syntax version number; it MUST be 0.
rid identifies the recipient's certificate or public key. * rid identifies the recipient's certificate or public key.
kem identifies the KEM algorithm; it MUST contain id-kem-rsa. * kem identifies the KEM algorithm; it MUST contain id-kem-rsa.
kemct is the ciphertext produced for this recipient; it contains C * kemct is the ciphertext produced for this recipient; it contains C
from steps 1 and 2 of Originator's Operations in Appendix A. from steps 1 and 2 of Originator's Operations in Appendix A.
kdf identifies the key-derivation function (KDF). Note that the * kdf identifies the key derivation function (KDF). Note that the
KDF used for CMS RecipientInfo process MAY be different than the KDF used for CMS RecipientInfo process MAY be different than the
KDF used within the RSA-KEM Algorithm. KDF used within the RSA-KEM algorithm.
kekLength is the size of the key-encryption key in octets. * kekLength is the size of the key-encryption key in octets.
ukm is an optional random input to the key-derivation function. * ukm is an optional random input to the key derivation function.
wrap identifies a key-encryption algorithm used to encrypt the * wrap identifies a key-encryption algorithm used to encrypt the
keying material. keying material.
encryptedKey is the result of encrypting the keying material with * encryptedKey is the result of encrypting the keying material with
the key-encryption key. When used with the CMS enveloped-data the key-encryption key. When used with the CMS enveloped-data
content type [RFC5652], the keying material is a content- content type [RFC5652], the keying material is a content-
encryption key. When used with the CMS authenticated-data content encryption key. When used with the CMS authenticated-data content
type [RFC5652], the keying material is a message-authentication type [RFC5652], the keying material is a message-authentication
key. When used with the CMS authenticated-enveloped-data content key. When used with the CMS authenticated-enveloped-data content
type [RFC5083], the keying material is a content-authenticated- type [RFC5083], the keying material is a content-authenticated-
encryption key. encryption key (CAEK).
NOTE: For backward compatibility, implementations MAY also support NOTE: For backward compatibility, implementations MAY also support
RSA-KEM Key Transport Algorithm, identified by id-rsa-kem-spki, which the RSA-KEM Key Transport algorithm, identified by id-rsa-kem-spki,
uses KeyTransRecipientInfo as specified in [RFC5990]. which uses KeyTransRecipientInfo as specified in [RFC5990].
2.3. Certificate Conventions 2.3. Certificate Conventions
The conventions specified in this section augment RFC 5280 [RFC5280]. The conventions specified in this section augment RFC 5280 [RFC5280].
A recipient who employs the RSA-KEM Algorithm MAY identify the public A recipient who employs the RSA-KEM algorithm MAY identify the public
key in a certificate by the same AlgorithmIdentifier as for the PKCS key in a certificate by the same AlgorithmIdentifier as for PKCS #1
#1 v1.5 algorithm, that is, using the rsaEncryption object identifier v1.5, that is, using the rsaEncryption object identifier [RFC8017].
[RFC8017]. The fact that the recipient will accept RSA-KEM with this The fact that the recipient will accept the RSA-KEM algorithm with
public key is not indicated by the use of this object identifier. this public key is not indicated by the use of this object
The willingness to accept the RSA-KEM Algorithm MAY be signaled by identifier. The willingness to accept the RSA-KEM algorithm MAY be
the use of the SMIMECapabilities Attribute as specified in signaled by the use of the SMIMECapabilities Attribute as specified
Section 2.5.2. of [RFC8551] or the SMIMECapabilities certificate in Section 2.5.2 of [RFC8551] or the SMIMECapabilities certificate
extension as specified in [RFC4262]. extension as specified in [RFC4262].
If the recipient wishes only to employ the RSA-KEM Algorithm with a If the recipient wishes only to employ the RSA-KEM algorithm with a
given public key, the recipient MUST identify the public key in the given public key, the recipient MUST identify the public key in the
certificate using the id-rsa-kem-spki object identifier; see certificate using the id-rsa-kem-spki object identifier; see
Appendix B. The use of the id-rsa-kem-spki object identifier allows Appendix B. The use of the id-rsa-kem-spki object identifier allows
certificates that were issued to be compatible with RSA-KEM Key certificates that were issued to be compatible with the RSA-KEM Key
Transport to also be used with this specification. When the id-rsa- Transport algorithm to also be used with this specification. When
kem-spki object identifier appears in the SubjectPublicKeyInfo the id-rsa-kem-spki object identifier appears in the
algorithm field of the certificate, the parameters field from SubjectPublicKeyInfo algorithm field of the certificate, the
AlgorithmIdentifier SHOULD be absent. That is, the parameters field from AlgorithmIdentifier SHOULD be absent. That is,
AlgorithmIdentifier SHOULD be a SEQUENCE of one component, the id- the AlgorithmIdentifier SHOULD be a SEQUENCE of one component, the
rsa-kem-spki object identifier. With absent parameters, the KDF3 id-rsa-kem-spki object identifier. With absent parameters, the KDF3
key-derivation function [ANS-X9.44] with SHA-256 [SHS] are used to key derivation function [ANS-X9.44] with SHA-256 [SHS] are used to
derive the shared secret. derive the shared secret.
When the AlgorithmIdentifier parameters are present, the When the AlgorithmIdentifier parameters are present, the
GenericHybridParameters MUST be used. Within the kem element, the GenericHybridParameters MUST be used. Within the kem element, the
algorithm identifier MUST be set to id-kem-rsa, and RsaKemParameters algorithm identifier MUST be set to id-kem-rsa, and RsaKemParameters
MUST be included. As described in Section 2.4, the MUST be included. As described in Section 2.4, the
GenericHybridParameters constrain the values that can be used with GenericHybridParameters constrain the values that can be used with
the RSA public key for the kdf, kekLength, and wrap fields of the the RSA public key for the kdf, kekLength, and wrap fields of the
KEMRecipientInfo structure. KEMRecipientInfo structure.
skipping to change at page 10, line 6 skipping to change at line 408
The intended application for the public key MAY be indicated in the The intended application for the public key MAY be indicated in the
key usage certificate extension as specified in Section 4.2.1.3 of key usage certificate extension as specified in Section 4.2.1.3 of
[RFC5280]. If the keyUsage extension is present in a certificate [RFC5280]. If the keyUsage extension is present in a certificate
that conveys an RSA public key with the id-rsa-kem-spki object that conveys an RSA public key with the id-rsa-kem-spki object
identifier as discussed above, then the key usage extension MUST identifier as discussed above, then the key usage extension MUST
contain only the following value: contain only the following value:
keyEncipherment keyEncipherment
Other keyUsage extension values MUST NOT be present. That is, a Other keyUsage extension values MUST NOT be present. That is, a
public key intended to be employed only with the RSA-KEM Algorithm public key intended to be employed only with the RSA-KEM algorithm
MUST NOT also be employed for data encryption or for digital MUST NOT also be employed for data encryption or for digital
signatures. Good cryptographic practice employs a given RSA key pair signatures. Good cryptographic practice employs a given RSA key pair
in only one scheme. This practice avoids the risk that vulnerability in only one scheme. This practice avoids the risk that vulnerability
in one scheme may compromise the security of the other, and may be in one scheme may compromise the security of the other and may be
essential to maintain provable security. essential to maintain provable security.
2.4. SMIMECapabilities Attribute Conventions 2.4. SMIMECapabilities Attribute Conventions
Section 2.5.2 of [RFC8551] defines the SMIMECapabilities attribute to Section 2.5.2 of [RFC8551] defines the SMIMECapabilities attribute to
announce a partial list of algorithms that an S/MIME implementation announce a partial list of algorithms that an S/MIME implementation
can support. When constructing a CMS signed-data content type can support. When constructing a CMS signed-data content type
[RFC5652], a compliant implementation MAY include the [RFC5652], a compliant implementation MAY include the
SMIMECapabilities attribute that announces support for the RSA-KEM SMIMECapabilities attribute that announces support for the RSA-KEM
Algorithm. algorithm.
The SMIMECapability SEQUENCE representing the RSA-KEM Algorithm MUST The SMIMECapability SEQUENCE representing the RSA-KEM algorithm MUST
include the id-rsa-kem-spki object identifier in the capabilityID include the id-rsa-kem-spki object identifier in the capabilityID
field; see Appendix B for the object identifier value, and see field; see Appendix B for the object identifier value and Appendix C
Appendix C for examples. When the id-rsa-kem-spki object identifier for examples. When the id-rsa-kem-spki object identifier appears in
appears in the capabilityID field and the parameters are present, the capabilityID field and the parameters are present, then the
then the parameters field MUST use the GenericHybridParameters type. parameters field MUST use the GenericHybridParameters type.
GenericHybridParameters ::= SEQUENCE { GenericHybridParameters ::= SEQUENCE {
kem KeyEncapsulationMechanism, kem KeyEncapsulationMechanism,
dem DataEncapsulationMechanism } dem DataEncapsulationMechanism }
The fields of the GenericHybridParameters type have the following The fields of the GenericHybridParameters type have the following
meanings: meanings:
kem is an AlgorithmIdentifer. The algorithm field MUST be set to * kem is an AlgorithmIdentifer. The algorithm field MUST be set to
id-kem-rsa, and the parameters field MUST be RsaKemParameters, id-kem-rsa, and the parameters field MUST be RsaKemParameters,
which is a SEQUENCE of an AlgorithmIdentifier that identifies the which is a SEQUENCE of an AlgorithmIdentifier that identifies the
supported key-derivation function and a positive INTEGER that supported key derivation function and a positive INTEGER that
identifies the length of the key-encryption key in octets. identifies the length of the key-encryption key in octets.
dem is an AlgorithmIdentifier. The algorithm field MUST be * dem is an AlgorithmIdentifier. The algorithm field MUST be
present, and it identifies the key-encryption algorithm. The present, and it identifies the key-encryption algorithm. The
parameters are optional. If the GenericHybridParameters are parameters are optional. If the GenericHybridParameters are
present, then the provided dem value MUST be used in the wrap present, then the provided dem value MUST be used in the wrap
field of KEMRecipientInfo. field of KEMRecipientInfo.
If the GenericHybridParameters are present, then the provided kem If the GenericHybridParameters are present, then the provided kem
value MUST be used as the key-derivation function in the kdf field of value MUST be used as the key derivation function in the kdf field of
KEMRecipientInfo, and the provided key length MUST be used in the KEMRecipientInfo and the provided key length MUST be used in the
kekLength of KEMRecipientInfo. kekLength of KEMRecipientInfo.
3. Security Considerations 3. Security Considerations
The RSA-KEM Algorithm should be considered as a replacement for the The RSA-KEM algorithm should be considered as a replacement for the
key transport portion of the widely implemented PKCS #1 v1.5 key transport portion of the widely implemented PKCS #1 v1.5
[RFC8017] for new applications that use CMS to avoid potential [RFC8017] for new applications that use CMS to avoid potential
vulnerabilities to chosen-ciphertext attacks and gain a tighter vulnerabilities to chosen-ciphertext attacks and gain a tighter
security proof; however, the RSA-KEM Algorithm has the disadvantage security proof. However, the RSA-KEM algorithm has the disadvantage
of slightly longer encrypted keying material. With PKCS #1 v1.5, the of slightly longer encrypted keying material. With PKCS #1 v1.5, the
originator encrypts the key-encryption key directly with the originator encrypts the key-encryption key directly with the
recipient's RSA public key. With the RSA-KEM, the key-encryption key recipient's RSA public key. With the RSA-KEM algorithm, the key-
is encrypted separately. encryption key is encrypted separately.
The security of the RSA-KEM Algorithm can be shown to be tightly The security of the RSA-KEM algorithm can be shown to be tightly
related to the difficulty of either solving the RSA problem, or related to the difficulty of either solving the RSA problem or
breaking the underlying symmetric key-encryption algorithm, if the breaking the underlying symmetric key-encryption algorithm if the
underlying key-derivation function is modeled as a random oracle, and underlying key derivation function is modeled as a random oracle,
assuming that the symmetric key-encryption algorithm satisfies the assuming that the symmetric key-encryption algorithm satisfies the
properties of a data encapsulation mechanism [SHOUP]. While in properties of a data encapsulation mechanism [SHOUP]. While in
practice a random-oracle result does not provide an actual security practice a random-oracle result does not provide an actual security
proof for any particular key-derivation function, the result does proof for any particular key derivation function, the result does
provide assurance that the general construction is reasonable; a key- provide assurance that the general construction is reasonable; a key
derivation function would need to be particularly weak to lead to an derivation function would need to be particularly weak to lead to an
attack that is not possible in the random-oracle model. attack that is not possible in the random-oracle model.
The RSA key size and the underlying components need to be selected The RSA key size and the underlying components need to be selected
consistent with the desired security level. Several security levels consistent with the desired security level. Several security levels
have been identified in the NIST SP 800-57 Part 1 have been identified in the NIST SP 800-57 Part 1
[NISTSP800-57pt1r5]. For example, one way to achieve 128-bit [NISTSP800-57pt1r5]. For example, one way to achieve 128-bit
security, the RSA key size would be at least 3072 bits, the key- security, the RSA key size would be at least 3072 bits, the key
derivation function would be SHA-256, and the symmetric key- derivation function would be SHA-256, and the symmetric key-
encryption algorithm would be AES Key Wrap with a 128-bit key. encryption algorithm would be AES Key Wrap with a 128-bit key.
Implementations MUST protect the RSA private key, the key-encryption Implementations MUST protect the RSA private key, the key-encryption
key, the content-encryption key, message-authentication key, and the key, the content-encryption key, message-authentication key, and the
content-authenticated-encryption key. Disclosure of the RSA private content-authenticated-encryption key. Disclosure of the RSA private
key could result in the compromise of all messages protected with key could result in the compromise of all messages protected with
that key. Disclosure of the key-encryption key, the content- that key. Disclosure of the key-encryption key, the content-
encryption key, or the content-authenticated-encryption key could encryption key, or the content-authenticated-encryption key could
result in compromise of the associated encrypted content. Disclosure result in compromise of the associated encrypted content. Disclosure
of the key-encryption key, the message-authentication key, or the of the key-encryption key, the message-authentication key, or the
content-authenticated-encryption key could allow modification of the content-authenticated-encryption key could allow modification of the
associated authenticated content. associated authenticated content.
Additional considerations related to key management may be found in Additional considerations related to key management may be found in
[NISTSP800-57pt1r5]. [NISTSP800-57pt1r5].
The security of the RSA-KEM Algorithm depends on a quality random The security of the RSA-KEM algorithm depends on a quality random
number generator. For further discussion on random number number generator. For further discussion on random number
generation, see [RFC4086]. generation, see [RFC4086].
The RSA-KEM Algorithm does not use an explicit padding scheme; The RSA-KEM algorithm does not use an explicit padding scheme.
instead, an encoded random value (z) between zero and the RSA modulus Instead, an encoded random value (z) between zero and the RSA modulus
minus one (n-1) is directly encrypted with the recipient's RSA public minus one (n-1) is directly encrypted with the recipient's RSA public
key. The IntegerToString(z, nLen) encoding produces a string that is key. The IntegerToString(z, nLen) encoding produces a string that is
the full length of the RSA modulus. In addition, the random value is the full length of the RSA modulus. In addition, the random value is
passed through a key-derivation function (KDF) to reduce possible passed through a KDF to reduce possible harm from a poorly
harm from a poorly implemented random number source or a maliciously implemented random number source or a maliciously chosen random value
chosen random value (z). Implementations MUST NOT use z directly for (z). Implementations MUST NOT use z directly for any purpose.
any purpose.
As long as a fresh random integer z is chosen as part of each As long as a fresh random integer z is chosen as part of each
invocation of the Encapsulate() function, RSA-KEM does not degrade as invocation of the Encapsulate() function, the RSA-KEM algorithm does
the number of ciphertexts increases. Since RSA encryption provides a not degrade as the number of ciphertexts increases. Since RSA
bijective map, a collision in the KDF is the only way that RSA-KEM encryption provides a bijective map, a collision in the KDF is the
can produce more than one ciphertext that encapsulates the same only way that the RSA-KEM algorithm can produce more than one
shared secret. ciphertext that encapsulates the same shared secret.
The RSA-KEM Algorithm provides a fixed-length ciphertext. The The RSA-KEM algorithm provides a fixed-length ciphertext. The
recipient MUST check that the received byte string is the expected recipient MUST check that the received byte string is the expected
length and the length corresponds to an integer in the expected range length and the length corresponds to an integer in the expected range
prior to attempting decryption with their RSA private key as prior to attempting decryption with their RSA private key as
described in Steps 1 and 2 of Appendix A.2. described in Steps 1 and 2 of Appendix A.2.
Implementations SHOULD NOT reveal information about intermediate Implementations SHOULD NOT reveal information about intermediate
values or calculations, whether by timing or other "side channels", values or calculations, whether by timing or other "side channels";
otherwise an opponent may be able to determine information about the otherwise, an opponent may be able to determine information about the
keying data and/or the recipient's private key. Although not all keying data and/or the recipient's private key. Although not all
intermediate information may be useful to an opponent, it is intermediate information may be useful to an opponent, it is
preferable to conceal as much information as is practical, unless preferable to conceal as much information as is practical, unless
analysis specifically indicates that the information would not be analysis specifically indicates that the information would not be
useful to an opponent. useful to an opponent.
Generally, good cryptographic practice employs a given RSA key pair Generally, good cryptographic practice employs a given RSA key pair
in only one scheme. This practice avoids the risk that vulnerability in only one scheme. This practice avoids the risk that vulnerability
in one scheme may compromise the security of the other, and may be in one scheme may compromise the security of the other, and may be
essential to maintain provable security. RSA public keys have often essential to maintain provable security. RSA public keys have often
been employed for multiple purposes such as key transport and digital been employed for multiple purposes such as key transport and digital
signature without any known bad interactions; however, such combined signature without any known bad interactions; however, such combined
use of an RSA key pair is NOT RECOMMENDED in the future (unless the use of an RSA key pair is NOT RECOMMENDED in the future (unless the
different schemes are specifically designed to be used together). different schemes are specifically designed to be used together).
Accordingly, an RSA key pair used for the RSA-KEM Algorithm SHOULD Accordingly, an RSA key pair used for the RSA-KEM algorithm SHOULD
NOT also be used for digital signatures. Indeed, the Accredited NOT also be used for digital signatures. Indeed, the Accredited
Standards Committee X9 (ASC X9) requires such a separation between Standards Committee X9 (ASC X9) requires such a separation between
key pairs used for key establishment and key pairs used for digital key pairs used for key establishment and key pairs used for digital
signature [ANS-X9.44]. Continuing this principle of key separation, signature [ANS-X9.44]. Continuing this principle of key separation,
a key pair used for the RSA-KEM Algorithm SHOULD NOT be used with a key pair used for the RSA-KEM algorithm SHOULD NOT be used with
other key establishment schemes, or for data encryption, or with more other key establishment schemes, or for data encryption, or with more
than one set of underlying algorithm components. than one set of underlying algorithm components.
It is acceptable to use the same RSA key pair for RSA-KEM Key It is acceptable to use the same RSA key pair for the RSA-KEM Key
Transport as specified in [RFC5990] and this specification. This is Transport algorithm as specified in [RFC5990] and this specification.
acceptable because the operations involving the RSA public key and This is acceptable because the operations involving the RSA public
the RSA private key are identical in the two specifications. key and the RSA private key are identical in the two specifications.
Parties can gain assurance that implementations are correct through Parties can gain assurance that implementations are correct through
formal implementation validation, such as the NIST Cryptographic formal implementation validation, such as the NIST Cryptographic
Module Validation Program (CMVP) [CMVP]. Module Validation Program (CMVP) [CMVP].
4. IANA Considerations 4. IANA Considerations
For the ASN.1 Module in Appendix B.2, IANA is requested to assign an For the ASN.1 Module in Appendix B.2, IANA has assigned an object
object identifier (OID) for the module identifier. The OID for the identifier (OID) for the module identifier. The OID for the module
module should be allocated in the "SMI Security for S/MIME Module has been allocated in the "SMI Security for S/MIME Module Identifier"
Identifier" registry (1.2.840.113549.1.9.16.0), and the Description registry (1.2.840.113549.1.9.16.0), and the Description for the new
for the new OID should be set to "id-mod-cms-rsa-kem-2023". OID has been set to "id-mod-cms-rsa-kem-2023".
IANA is requested to update the id-alg-rsa-kem entry in the SMI IANA has updated the id-alg-rsa-kem entry in the "SMI Security for S/
Security for S/MIME Algorithms (1.2.840.113549.1.9.16.3) repository MIME Algorithms (1.2.840.113549.1.9.16.3)" repository to refer to
to refer to this document. In addition, IANA is requested to add the this document. In addition, IANA has added the following note to the
following note to the registry: registry:
Value 14, "id-alg-rsa-kem," is also referred to as "id-rsa-kem-spki." Value 14, "id-alg-rsa-kem," is also referred to as "id-rsa-kem-spki."
5. References 5. References
5.1. Normative References 5.1. Normative References
[ANS-X9.44] [ANS-X9.44]
American National Standards Institute, "Public Key American National Standards Institute, "Public Key
Cryptography for the Financial Services Industry -- Key Cryptography for the Financial Services Industry -- Key
Establishment Using Integer Factorization Cryptography", Establishment Using Integer Factorization Cryptography",
American National Standard X9.44, 2007. ANSI X9.44-2007 (R2017), 2007,
<https://webstore.ansi.org/standards/ascx9/
[I-D.ietf-lamps-cms-kemri] ansix9442007r2017>.
Housley, R., Gray, J., and T. Okubo, "Using Key
Encapsulation Mechanism (KEM) Algorithms in the
Cryptographic Message Syntax (CMS)", Work in Progress,
Internet-Draft, draft-ietf-lamps-cms-kemri-08, 6 February
2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
lamps-cms-kemri-08>.
[ISO18033-2] [ISO18033-2]
ISO/IEC JTC 1/SC 27, "Information technology -- Security ISO/IEC, "Information technology -- Security techniques --
techniques -- Encryption algorithms -- Part 2: Asymmetric Encryption algorithms -- Part 2: Asymmetric ciphers", ISO/
ciphers", ISO/IEC 18033-2:2006, 2006, IEC 18033-2:2006, 2006,
<https://www.iso.org/standard/37971.html>. <https://www.iso.org/standard/37971.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard [RFC3394] Schaad, J. and R. Housley, "Advanced Encryption Standard
(AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394, (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394,
September 2002, <https://www.rfc-editor.org/info/rfc3394>. September 2002, <https://www.rfc-editor.org/info/rfc3394>.
skipping to change at page 15, line 10 skipping to change at line 650
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/ [RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/
Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Multipurpose Internet Mail Extensions (S/MIME) Version 4.0
Message Specification", RFC 8551, DOI 10.17487/RFC8551, Message Specification", RFC 8551, DOI 10.17487/RFC8551,
April 2019, <https://www.rfc-editor.org/info/rfc8551>. April 2019, <https://www.rfc-editor.org/info/rfc8551>.
[RFC9629] Housley, R., Gray, J., and T. Okubo, "Using Key
Encapsulation Mechanism (KEM) Algorithms in the
Cryptographic Message Syntax (CMS)", RFC 9629,
DOI 10.17487/RFC9629, August 2024,
<https://www.rfc-editor.org/info/rfc9629>.
[SHS] National Institute of Standards and Technology, "Secure [SHS] National Institute of Standards and Technology, "Secure
Hash Standard", DOI 10.6028/nist.fips.180-4, July 2015, Hash Standard", NIST FIPS PUB 180-4,
<https://doi.org/10.6028/nist.fips.180-4>. DOI 10.6028/NIST.FIPS.180-4, July 2015,
<https://doi.org/10.6028/NIST.FIPS.180-4>.
[X.680] ITU-T, "Information technology -- Abstract Syntax Notation [X.680] ITU-T, "Information technology - Abstract Syntax Notation
One (ASN.1): Specification of basic notation", ITU-T One (ASN.1): Specification of basic notation", ITU-T
Recommendation X.680, ISO/IEC 8824-1:2021, February 2021, Recommendation X.680, ISO/IEC 8824-1:2021, February 2021,
<https://www.itu.int/rec/T-REC-X.680>. <https://www.itu.int/rec/T-REC-X.680>.
[X.690] ITU-T, "Information technology -- ASN.1 encoding rules: [X.690] ITU-T, "Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER), Canonical Specification of Basic Encoding Rules (BER), Canonical
Encoding Rules (CER) and Distinguished Encoding Rules Encoding Rules (CER) and Distinguished Encoding Rules
(DER)", ITU-T Recommendation X.690, ISO/IEC 8825-1:2021, (DER)", ITU-T Recommendation X.690, ISO/IEC 8825-1:2021,
February 2021, <https://www.itu.int/rec/T-REC-X.680>. February 2021, <https://www.itu.int/rec/T-REC-X.690>.
5.2. Informative References 5.2. Informative References
[CMVP] National Institute of Standards and Technology, [CMVP] National Institute of Standards and Technology,
"Cryptographic Module Validation Program", 2016, "Cryptographic Module Validation Program", 2016,
<https://csrc.nist.gov/projects/cryptographic-module- <https://csrc.nist.gov/projects/cryptographic-module-
validation-program>. validation-program>.
[NISTSP800-57pt1r5] [NISTSP800-57pt1r5]
National Institute of Standards and Technology, Barker, E., "Recommendation for Key Management: Part 1 -
"Recommendation for Key Management:Part 1 - General", General", NIST SP 800-57, Part 1, Revision 5,
DOI 10.6028/nist.sp.800-57pt1r5, May 2020, DOI 10.6028/nist.sp.800-57pt1r5, May 2020,
<https://doi.org/10.6028/nist.sp.800-57pt1r5>. <https://doi.org/10.6028/nist.sp.800-57pt1r5>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086, "Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005, DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>. <https://www.rfc-editor.org/info/rfc4086>.
[RFC4262] Santesson, S., "X.509 Certificate Extension for Secure/ [RFC4262] Santesson, S., "X.509 Certificate Extension for Secure/
Multipurpose Internet Mail Extensions (S/MIME) Multipurpose Internet Mail Extensions (S/MIME)
skipping to change at page 16, line 16 skipping to change at line 712
Considerations for the SHA-0 and SHA-1 Message-Digest Considerations for the SHA-0 and SHA-1 Message-Digest
Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011, Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
<https://www.rfc-editor.org/info/rfc6194>. <https://www.rfc-editor.org/info/rfc6194>.
[SHOUP] Shoup, V., "A Proposal for an ISO Standard for Public Key [SHOUP] Shoup, V., "A Proposal for an ISO Standard for Public Key
Encryption", Cryptology ePrint Archive Paper 2001/112, Encryption", Cryptology ePrint Archive Paper 2001/112,
2001, <https://eprint.iacr.org/2001/112>. 2001, <https://eprint.iacr.org/2001/112>.
Appendix A. RSA-KEM Algorithm Appendix A. RSA-KEM Algorithm
The RSA-KEM Algorithm is a one-pass (store-and-forward) cryptographic The RSA-KEM algorithm is a one-pass (store-and-forward) cryptographic
mechanism for an originator to securely send keying material to a mechanism for an originator to securely send keying material to a
recipient using the recipient's RSA public key. recipient using the recipient's RSA public key.
With the RSA-KEM Algorithm, an originator encrypts a random integer With the RSA-KEM algorithm, an originator encrypts a random integer
(z) with the recipient's RSA public key to produce a ciphertext (ct), (z) with the recipient's RSA public key to produce a ciphertext (ct),
and the originator derives a shared secret (SS) from the random and the originator derives a shared secret (SS) from the random
integer (z). The originator then sends the ciphertext (ct) to the integer (z). The originator then sends the ciphertext (ct) to the
recipient. The recipient decrypts the ciphertext (ct) using their recipient. The recipient decrypts the ciphertext (ct) using their
private key to recover the random integer (z), and the recipient private key to recover the random integer (z), and the recipient
derives a shared secret (SS) from the random integer(z). In this derives a shared secret (SS) from the random integer (z). In this
way, originator and recipient obtain the same shared secret (SS). way, the originator and recipient obtain the same shared secret (SS).
The RSA-KEM Algorithm depends on a key-derivation function (KDF), The RSA-KEM algorithm depends on a key derivation function (KDF),
which is used to derive the shared secret (SS). Many key-derivation which is used to derive the shared secret (SS). Many key derivation
functions support the inclusion of other information in addition to functions support the inclusion of other information in addition to
the shared secret (SS) in the input to the function; however, no the shared secret (SS) in the input to the function; however, no
other information is included as an input to the KDF by the RSA-KEM other information is included as an input to the KDF by the RSA-KEM
Algorithm. algorithm.
A.1. Originator's Operations: RSA-KEM Encapsulate() A.1. Originator's Operations: RSA-KEM Encapsulate()
Let (n,e) be the recipient's RSA public key; see [RFC8017] for Let (n,e) be the recipient's RSA public key; see [RFC8017] for
details. details.
Let nLen denote the length in bytes of the modulus n, i.e., the least Let nLen denote the length in bytes of the modulus n, i.e., the least
integer such that 2^(8*nLen) > n. integer such that 2^(8*nLen) > n.
The originator performs the following operations: The originator performs the following operations:
1. Generate a random integer z between 0 and n-1 (see note), and 1. Generate a random integer z between 0 and n-1 (see NOTE below),
convert z to a byte string Z of length nLen, most significant and convert z to a byte string Z of length nLen, most significant
byte first: byte first:
z = RandomInteger (0, n-1) z = RandomInteger (0, n-1)
Z = IntegerToString (z, nLen) Z = IntegerToString (z, nLen)
2. Encrypt the random integer z using the recipient's RSA public key 2. Encrypt the random integer z using the recipient's RSA public key
(n,e), and convert the resulting integer c to a ciphertext C, a (n,e) and convert the resulting integer c to a ciphertext C, a
byte string of length nLen: byte string of length nLen:
c = z^e mod n c = z^e mod n
ct = IntegerToString (c, nLen) ct = IntegerToString (c, nLen)
3. Derive a symmetric shared secret SS of length ssLen bytes (which 3. Derive a symmetric shared secret SS of length ssLen bytes (which
MUST be the length of the key-encryption key) from the byte MUST be the length of the key-encryption key) from the byte
string Z using the underlying key-derivation function: string Z using the underlying key derivation function:
SS = KDF (Z, ssLen) SS = KDF (Z, ssLen)
4. Output the shared secret SS and the ciphertext ct. Send the 4. Output the shared secret SS and the ciphertext ct. Send the
ciphertext ct to the recipient. ciphertext ct to the recipient.
NOTE: The random integer z MUST be generated independently at random NOTE: The random integer z MUST be generated independently at random
for different encryption operations, whether for the same or for different encryption operations, whether for the same or
different recipients. different recipients.
skipping to change at page 18, line 11 skipping to change at line 804
recover an integer z (see NOTE below): recover an integer z (see NOTE below):
z = c^d mod n z = c^d mod n
4. Convert the integer z to a byte string Z of length nLen, most 4. Convert the integer z to a byte string Z of length nLen, most
significant byte first (see NOTE below): significant byte first (see NOTE below):
Z = IntegerToString (z, nLen) Z = IntegerToString (z, nLen)
5. Derive a shared secret SS of length ssLen bytes from the byte 5. Derive a shared secret SS of length ssLen bytes from the byte
string Z using the key-derivation function (see NOTE below): string Z using the key derivation function (see NOTE below):
SS = KDF (Z, ssLen) SS = KDF (Z, ssLen)
6. Output the shared secret SS. 6. Output the shared secret SS.
NOTE: Implementations SHOULD NOT reveal information about the integer NOTE: Implementations SHOULD NOT reveal information about the integer
z, the string Z, or about the calculation of the exponentiation in z, the string Z, or about the calculation of the exponentiation in
Step 2, the conversion in Step 3, or the key derivation in Step 4, Step 2, the conversion in Step 3, or the key derivation in Step 4,
whether by timing or other "side channels". The observable behavior whether by timing or other "side channels". The observable behavior
of the implementation SHOULD be the same at these steps for all of the implementation SHOULD be the same at these steps for all
ciphertexts C that are in range. For example, IntegerToString ciphertexts C that are in range. For example, IntegerToString
conversion should take the same amount of time regardless of the conversion should take the same amount of time regardless of the
actual value of the integer z. The integer z, the string Z, and actual value of the integer z. The integer z, the string Z, and
other intermediate results MUST be securely deleted when they are no other intermediate results MUST be securely deleted when they are no
longer needed. longer needed.
Appendix B. ASN.1 Syntax Appendix B. ASN.1 Syntax
The ASN.1 syntax for identifying the RSA-KEM Algorithm is an The ASN.1 syntax for identifying the RSA-KEM algorithm is an
extension of the syntax for the "generic hybrid cipher" in ANS X9.44 extension of the syntax for the "generic hybrid cipher" in ANS X9.44
[ANS-X9.44]. [ANS-X9.44].
The ASN.1 Module is unchanged from RFC 5990. The id-rsa-kem-spki The ASN.1 Module is unchanged from RFC 5990. The id-rsa-kem-spki
object identifier is used in a backward compatible manner in object identifier is used in a backward compatible manner in
certificates [RFC5280] and SMIMECapabilities [RFC8551]. Of course, certificates [RFC5280] and SMIMECapabilities [RFC8551]. Of course,
the use of the id-kem-rsa object identifier in the new the use of the id-kem-rsa object identifier in the new
KEMRecipientInfo structure [I-D.ietf-lamps-cms-kemri] was not yet KEMRecipientInfo structure [RFC9629] was not yet defined at the time
defined at the time that RFC 5990 was written. that RFC 5990 was written.
B.1. Underlying Components B.1. Underlying Components
Implementations that conform to this specification MUST support the Implementations that conform to this specification MUST support the
KDF3 [ANS-X9.44] key-derivation function using SHA-256 [SHS]. KDF3 [ANS-X9.44] key derivation function using SHA-256 [SHS].
KDF2 [ANS-X9.44] and KDF3 are both key-derivation functions based on KDF2 [ANS-X9.44] and KDF3 are both key derivation functions based on
a hash function. The only difference between KDF2 and KDF3 is the a hash function. The only difference between KDF2 and KDF3 is the
order of the components to be hashed. order of the components to be hashed.
KDF2 calculates T as: T = T || Hash (Z || D || otherInfo) KDF2 calculates T as: T = T || Hash (Z || D || otherInfo)
KDF3 calculates T as: T = T || Hash (D || Z || otherInfo) KDF3 calculates T as: T = T || Hash (D || Z || otherInfo)
The object identifier for KDF3 is: The object identifier for KDF3 is:
id-kdf-kdf3 OBJECT IDENTIFIER ::= { x9-44-components kdf3(2) } id-kdf-kdf3 OBJECT IDENTIFIER ::= { x9-44-components kdf3(2) }
The KDF3 parameters identify the underlying hash function. For The KDF3 parameters identify the underlying hash function. For
alignment with the ANS X9.44, the hash function MUST be an ASC alignment with ANS X9.44, the hash function MUST be an ASC
X9-approved hash function. While the SHA-1 hash algorithm is X9-approved hash function. While the SHA-1 hash algorithm is
included in the ASN.1 definitions, SHA-1 MUST NOT be used. SHA-1 is included in the ASN.1 definitions, SHA-1 MUST NOT be used. SHA-1 is
considered to be obsolete; see [RFC6194]. SHA-1 remains in the ASN.1 considered to be obsolete; see [RFC6194]. SHA-1 remains in the ASN.1
module for compatibility with RFC 5990. In addition, other hash module for compatibility with RFC 5990. In addition, other hash
functions MAY be used with CMS. functions MAY be used with CMS.
kda-kdf3 KEY-DERIVATION ::= { kda-kdf3 KEY-DERIVATION ::= {
IDENTIFIER id-kdf-kdf3 IDENTIFIER id-kdf-kdf3
PARAMS TYPE KDF3-HashFunction ARE required PARAMS TYPE KDF3-HashFunction ARE required
-- No S/MIME caps defined -- } -- No S/MIME caps defined -- }
skipping to change at page 20, line 7 skipping to change at line 897
PARAMS ARE absent PARAMS ARE absent
SMIME-CAPS { IDENTIFIED BY id-aes192-wrap } } SMIME-CAPS { IDENTIFIED BY id-aes192-wrap } }
kwa-aes256-wrap KEY-WRAP ::= { kwa-aes256-wrap KEY-WRAP ::= {
IDENTIFIER id-aes256-wrap IDENTIFIER id-aes256-wrap
PARAMS ARE absent PARAMS ARE absent
SMIME-CAPS { IDENTIFIED BY id-aes256-wrap } } SMIME-CAPS { IDENTIFIED BY id-aes256-wrap } }
B.2. ASN.1 Module B.2. ASN.1 Module
RFC EDITOR: Please replace TBD2 with the value assigned by IANA
during the publication of [I-D.ietf-lamps-cms-kemri].
<CODE BEGINS> <CODE BEGINS>
CMS-RSA-KEM-2023 CMS-RSA-KEM-2023
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
pkcs-9(9) smime(16) modules(0) id-mod-cms-rsa-kem-2023(TBD1) } pkcs-9(9) smime(16) modules(0) id-mod-cms-rsa-kem-2023(79) }
DEFINITIONS EXPLICIT TAGS ::= BEGIN DEFINITIONS EXPLICIT TAGS ::= BEGIN
-- EXPORTS ALL -- EXPORTS ALL
IMPORTS IMPORTS
KEM-ALGORITHM KEM-ALGORITHM
FROM KEMAlgorithmInformation-2023 -- [I-D.ietf-lamps-cms-kemri] FROM KEMAlgorithmInformation-2023 -- [RFC9629]
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-kemAlgorithmInformation-2023(TBD2) } id-mod-kemAlgorithmInformation-2023(109) }
AlgorithmIdentifier{}, PUBLIC-KEY, DIGEST-ALGORITHM, AlgorithmIdentifier{}, PUBLIC-KEY, DIGEST-ALGORITHM,
KEY-DERIVATION, KEY-WRAP, SMIME-CAPS KEY-DERIVATION, KEY-WRAP, SMIME-CAPS
FROM AlgorithmInformation-2009 -- [RFC5912] FROM AlgorithmInformation-2009 -- [RFC5912]
{ iso(1) identified-organization(3) dod(6) internet(1) { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-algorithmInformation-02(58) } id-mod-algorithmInformation-02(58) }
kwa-aes128-wrap, kwa-aes192-wrap, kwa-aes256-wrap kwa-aes128-wrap, kwa-aes192-wrap, kwa-aes256-wrap
FROM CMSAesRsaesOaep-2009 -- [RFC5911] FROM CMSAesRsaesOaep-2009 -- [RFC5911]
skipping to change at page 21, line 42 skipping to change at line 978
pkcs-1 OID ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs-1 OID ::= { iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs-1(1) } pkcs(1) pkcs-1(1) }
-- X9.44 arc -- X9.44 arc
x9-44 OID ::= { iso(1) identified-organization(3) tc68(133) x9-44 OID ::= { iso(1) identified-organization(3) tc68(133)
country(16) x9(840) x9Standards(9) x9-44(44) } country(16) x9(840) x9Standards(9) x9-44(44) }
x9-44-components OID ::= { x9-44 components(1) } x9-44-components OID ::= { x9-44 components(1) }
-- RSA-KEM Algorithm -- RSA-KEM algorithm
id-rsa-kem OID ::= { iso(1) member-body(2) us(840) rsadsi(113549) id-rsa-kem OID ::= { iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs-9(9) smime(16) alg(3) 14 } pkcs(1) pkcs-9(9) smime(16) alg(3) 14 }
id-rsa-kem-spki OID ::= id-rsa-kem id-rsa-kem-spki OID ::= id-rsa-kem
GenericHybridParameters ::= SEQUENCE { GenericHybridParameters ::= SEQUENCE {
kem KeyEncapsulationMechanism, kem KeyEncapsulationMechanism,
dem DataEncapsulationMechanism } dem DataEncapsulationMechanism }
skipping to change at page 24, line 38 skipping to change at line 1117
kwa-camellia192-wrap.&smimeCaps | kwa-camellia192-wrap.&smimeCaps |
kwa-camellia256-wrap.&smimeCaps, kwa-camellia256-wrap.&smimeCaps,
... } ... }
END END
<CODE ENDS> <CODE ENDS>
Appendix C. SMIMECapabilities Examples Appendix C. SMIMECapabilities Examples
To indicate support for the RSA-KEM algorithm coupled with the KDF3 To indicate support for the RSA-KEM algorithm coupled with the KDF3
key-derivation function with SHA-256 and the AES Key Wrap symmetric key derivation function with SHA-256 and the AES Key Wrap symmetric
key-encryption algorithm 128-bit key-encryption key, the key-encryption algorithm 128-bit key-encryption key, the
SMIMECapabilities will include the following entry: SMIMECapabilities will include the following entry:
SEQUENCE { SEQUENCE {
id-rsa-kem-spki, -- RSA-KEM Algorithm id-rsa-kem-spki, -- RSA-KEM algorithm
SEQUENCE { -- GenericHybridParameters SEQUENCE { -- GenericHybridParameters
SEQUENCE { -- key encapsulation mechanism SEQUENCE { -- key encapsulation mechanism
id-kem-rsa, -- RSA-KEM id-kem-rsa, -- RSA-KEM
SEQUENCE { -- RsaKemParameters SEQUENCE { -- RsaKemParameters
SEQUENCE { -- key derivation function SEQUENCE { -- key derivation function
id-kdf-kdf3, -- KDF3 id-kdf-kdf3, -- KDF3
SEQUENCE { -- KDF3-HashFunction SEQUENCE { -- KDF3-HashFunction
id-sha256 -- SHA-256; no parameters (preferred) id-sha256 -- SHA-256; no parameters (preferred)
}, },
16 -- KEK length in bytes 16 -- KEK length in bytes
skipping to change at page 25, line 42 skipping to change at line 1158
30 1e 30 1e
30 19 30 19
06 0a 2b 81 05 10 86 48 09 2c 01 02 -- id-kdf-kdf3 06 0a 2b 81 05 10 86 48 09 2c 01 02 -- id-kdf-kdf3
30 0b 30 0b
06 09 60 86 48 01 65 03 04 02 01 -- id-sha256 06 09 60 86 48 01 65 03 04 02 01 -- id-sha256
02 01 10 -- 16 bytes 02 01 10 -- 16 bytes
30 0b 30 0b
06 09 60 86 48 01 65 03 04 01 05 -- id-aes128-Wrap 06 09 60 86 48 01 65 03 04 01 05 -- id-aes128-Wrap
To indicate support for the RSA-KEM algorithm coupled with the KDF3 To indicate support for the RSA-KEM algorithm coupled with the KDF3
key-derivation function with SHA-384 and the AES Key Wrap symmetric key derivation function with SHA-384 and the AES Key Wrap symmetric
key-encryption algorithm 192-bit key-encryption key, the key-encryption algorithm 192-bit key-encryption key, the
SMIMECapabilities will include the following SMIMECapability value SMIMECapabilities will include the following SMIMECapability value
(in hexadecimal): (in hexadecimal):
30 47 06 0b 2a 86 48 86 f7 0d 01 09 10 03 0e 30 30 47 06 0b 2a 86 48 86 f7 0d 01 09 10 03 0e 30
38 30 29 06 07 28 81 8c 71 02 02 04 30 1e 30 19 38 30 29 06 07 28 81 8c 71 02 02 04 30 1e 30 19
06 0a 2b 81 05 10 86 48 09 2c 01 02 30 0b 06 09 06 0a 2b 81 05 10 86 48 09 2c 01 02 30 0b 06 09
60 86 48 01 65 03 04 02 02 02 01 18 30 0b 06 09 60 86 48 01 65 03 04 02 02 02 01 18 30 0b 06 09
60 86 48 01 65 03 04 01 19 60 86 48 01 65 03 04 01 19
To indicate support for the RSA-KEM algorithm coupled with the KDF3 To indicate support for the RSA-KEM algorithm coupled with the KDF3
key-derivation function with SHA-512 and the AES Key Wrap symmetric key derivation function with SHA-512 and the AES Key Wrap symmetric
key-encryption algorithm 256-bit key-encryption key, the key-encryption algorithm 256-bit key-encryption key, the
SMIMECapabilities will include the following SMIMECapability value SMIMECapabilities will include the following SMIMECapability value
(in hexadecimal): (in hexadecimal):
30 47 06 0b 2a 86 48 86 f7 0d 01 09 10 03 0e 30 30 47 06 0b 2a 86 48 86 f7 0d 01 09 10 03 0e 30
38 30 29 06 07 28 81 8c 71 02 02 04 30 1e 30 19 38 30 29 06 07 28 81 8c 71 02 02 04 30 1e 30 19
06 0a 2b 81 05 10 86 48 09 2c 01 02 30 0b 06 09 06 0a 2b 81 05 10 86 48 09 2c 01 02 30 0b 06 09
60 86 48 01 65 03 04 02 03 02 01 20 30 0b 06 09 60 86 48 01 65 03 04 02 03 02 01 20 30 0b 06 09
60 86 48 01 65 03 04 01 2d 60 86 48 01 65 03 04 01 2d
Appendix D. RSA-KEM CMS Enveloped-Data Example Appendix D. RSA-KEM CMS Enveloped-Data Example
This example shows the establishment of an AES-128 content-encryption This example shows the establishment of an AES-128 content-encryption
key using: key using:
* RSA-KEM with a 3072-bit key and KDF3 with SHA-256; * RSA-KEM with a 3072-bit key and KDF3 with SHA-256;
* KEMRecipientInfo key derivation using KDF3 with SHA-256; and * KEMRecipientInfo key derivation using KDF3 with SHA-256; and
* KEMRecipientInfo key wrap using AES-128-KEYWRAP. * KEMRecipientInfo Key Wrap using AES-128-KEYWRAP.
In real-world use, the originator would encrypt the content- In real-world use, the originator would encrypt the content-
encryption key in a manner that would allow decryption with their own encryption key in a manner that would allow decryption with their own
private key as well as the recipient's private key. This is omitted private key as well as the recipient's private key. This is omitted
in an attempt to simplify the example. in an attempt to simplify the example.
D.1. Originator RSA-KEM Encapsulate() Processing D.1. Originator RSA-KEM Encapsulate() Processing
Alice obtains Bob's public key: Alice obtains Bob's public key:
skipping to change at page 27, line 20 skipping to change at line 1232
0875990b614e406fa6dff500043cbca95968faba61f795096a7fb3687a51078c 0875990b614e406fa6dff500043cbca95968faba61f795096a7fb3687a51078c
4ca2cb663366b0bea0cd9cccac72a25f3f4ed03deb68b4453bba44b943f4367b 4ca2cb663366b0bea0cd9cccac72a25f3f4ed03deb68b4453bba44b943f4367b
67d6cd10c8ace53f545aac50968fc3c6ecc80f3224b64e37038504e2d2c0e2b2 67d6cd10c8ace53f545aac50968fc3c6ecc80f3224b64e37038504e2d2c0e2b2
9d45e46c62826d96331360e4c17ea3ef89a9efc5fac99eda830e81450b6534dc 9d45e46c62826d96331360e4c17ea3ef89a9efc5fac99eda830e81450b6534dc
0bdf042b8f3b706649c631fe51fc2445cc8d447203ec2f41f79cdfea16de1ce6 0bdf042b8f3b706649c631fe51fc2445cc8d447203ec2f41f79cdfea16de1ce6
abdfdc1e2ef2e5d5d8a65e645f397240ef5a26f5e4ff715de782e30ecf477293 abdfdc1e2ef2e5d5d8a65e645f397240ef5a26f5e4ff715de782e30ecf477293
e89e13171405909a8e04dd31d21d0c57935fc1ceea8e1033e31e1bc8c56da0f3 e89e13171405909a8e04dd31d21d0c57935fc1ceea8e1033e31e1bc8c56da0f3
d79510f3f380ff58e5a61d361f2f18e99fbae5663172e8cd1f21deaddc5bbbea d79510f3f380ff58e5a61d361f2f18e99fbae5663172e8cd1f21deaddc5bbbea
060d55f1842b93d1a9c888d0bf85d0af9947fe51acf940c7e7577eb79cabecb3 060d55f1842b93d1a9c888d0bf85d0af9947fe51acf940c7e7577eb79cabecb3
Alice encrypts integer z using the Bob's RSA public key, the result Alice encrypts integer z using the Bob's RSA public key. The result
is called ct: is called ct:
c071fc273af8e7bdb152e06bf73310361074154a43abcf3c93c13499d2065344 c071fc273af8e7bdb152e06bf73310361074154a43abcf3c93c13499d2065344
3eed9ef5d3c0685e4aa76a6854815bb97691ff9f8dac15eea7d74f452bf350a6 3eed9ef5d3c0685e4aa76a6854815bb97691ff9f8dac15eea7d74f452bf350a6
46163d68288e978cbf7a73089ee52712f9a4f49e06ace7bbc85ab14d4e336c97 46163d68288e978cbf7a73089ee52712f9a4f49e06ace7bbc85ab14d4e336c97
c5728a2654138c7b26e8835c6b0a9fbed26495c4eadf745a2933be283f6a88b1 c5728a2654138c7b26e8835c6b0a9fbed26495c4eadf745a2933be283f6a88b1
6695fc06666873cfb6d36718ef3376cefc100c3941f3c494944078325807a559 6695fc06666873cfb6d36718ef3376cefc100c3941f3c494944078325807a559
186b95ccabf3714cfaf79f83bd30537fdd9aed5a4cdcbd8bd0486faed73e9d48 186b95ccabf3714cfaf79f83bd30537fdd9aed5a4cdcbd8bd0486faed73e9d48
6b3087d6c806546b6e2671575c98461e441f65542bd95de26d0f53a64e7848d7 6b3087d6c806546b6e2671575c98461e441f65542bd95de26d0f53a64e7848d7
31d9608d053e8d345546602d86236ffe3704c98ad59144f3089e5e6d527b5497 31d9608d053e8d345546602d86236ffe3704c98ad59144f3089e5e6d527b5497
skipping to change at page 28, line 5 skipping to change at line 1262
D.2. Originator CMS Processing D.2. Originator CMS Processing
Alice encodes the CMSORIforKEMOtherInfo structure with the algorithm Alice encodes the CMSORIforKEMOtherInfo structure with the algorithm
identifier for AES-128-KEYWRAP and a key length of 16 octets. The identifier for AES-128-KEYWRAP and a key length of 16 octets. The
DER encoding of CMSORIforKEMOtherInfo produces 18 octets: DER encoding of CMSORIforKEMOtherInfo produces 18 octets:
3010300b0609608648016503040105020110 3010300b0609608648016503040105020110
The CMSORIforKEMOtherInfo structure contains: The CMSORIforKEMOtherInfo structure contains:
0 16: SEQUENCE { 0 16: SEQUENCE {
2 11: SEQUENCE { 2 11: SEQUENCE {
4 9: OBJECT IDENTIFIER aes128-wrap (2 16 840 1 101 3 4 1 5) 4 9: OBJECT IDENTIFIER aes128-wrap (2 16 840 1 101 3 4 1 5)
: } : }
15 1: INTEGER 16 15 1: INTEGER 16
: } : }
Alice derives the key-encryption key from shared secret produced by Alice derives the key-encryption key from shared secret produced by
RSA-KEM Encapsulate() and the CMSORIforKEMOtherInfo structure with RSA-KEM Encapsulate() and the CMSORIforKEMOtherInfo structure with
KDF3 and SHA-256, the KEK is: KDF3 and SHA-256. The KEK is:
e6dc9d62ff2b469bef604c617b018718 e6dc9d62ff2b469bef604c617b018718
Alice randomly generates a 128-bit content-encryption key: Alice randomly generates a 128-bit content-encryption key:
77f2a84640304be7bd42670a84a1258b 77f2a84640304be7bd42670a84a1258b
Alice uses AES-128-KEYWRAP to encrypt the 128-bit content-encryption Alice uses AES-128-KEYWRAP to encrypt the 128-bit content-encryption
key with the derived key-encryption key: key with the derived key-encryption key:
skipping to change at page 29, line 21 skipping to change at line 1317
BlRrbiZxV1yYRh5EH2VUK9ld4m0PU6ZOeEjXMdlgjQU+jTRVRmAthiNv/jcEyYrV BlRrbiZxV1yYRh5EH2VUK9ld4m0PU6ZOeEjXMdlgjQU+jTRVRmAthiNv/jcEyYrV
kUTzCJ5ebVJ7VJe6EDx51i6A0CNUELBvcafZvRw4AA+RDWMS6i8go1V1Na0Bswk/ kUTzCJ5ebVJ7VJe6EDx51i6A0CNUELBvcafZvRw4AA+RDWMS6i8go1V1Na0Bswk/
tffuUHCA0Pd9SMnDs3lva33TeGCF+4lRI/BMofHBviLHR6jfrOMjcPsNVweD4n27 tffuUHCA0Pd9SMnDs3lva33TeGCF+4lRI/BMofHBviLHR6jfrOMjcPsNVweD4n27
fnT8qU7jlnb949ipVT2HgiRzbjfhkdq5U8fiKMB61coxIkIcFN69ByqatjAbBgor fnT8qU7jlnb949ipVT2HgiRzbjfhkdq5U8fiKMB61coxIkIcFN69ByqatjAbBgor
gQUQhkgJLAECMA0GCWCGSAFlAwQCAQUAAgEQMAsGCWCGSAFlAwQBBQQYKHguXT15 gQUQhkgJLAECMA0GCWCGSAFlAwQCAQUAAgEQMAsGCWCGSAFlAwQBBQQYKHguXT15
SnYWuGP7z8cZt48S3gjPKG4JMDwGCSqGSIb3DQEHATAdBglghkgBZQMEAQIEEEgM SnYWuGP7z8cZt48S3gjPKG4JMDwGCSqGSIb3DQEHATAdBglghkgBZQMEAQIEEEgM
yv66vvrO263eyviId4GAEMbKZdt73Xaw834vq2Jktm0= yv66vvrO263eyviId4GAEMbKZdt73Xaw834vq2Jktm0=
This result decodes to: This result decodes to:
0 604: SEQUENCE { 0 604: SEQUENCE {
4 9: OBJECT IDENTIFIER envelopedData (1 2 840 113549 1 7 3) 4 9: OBJECT IDENTIFIER envelopedData (1 2 840 113549 1 7 3)
15 589: [0] { 15 589: [0] {
19 585: SEQUENCE { 19 585: SEQUENCE {
23 1: INTEGER 3 23 1: INTEGER 3
26 516: SET { 26 516: SET {
30 512: [4] { 30 512: [4] {
34 11: OBJECT IDENTIFIER 34 11: OBJECT IDENTIFIER
: KEMRecipientInfo (1 2 840 113549 1 9 16 13 3) : KEMRecipientInfo (1 2 840 113549 1 9 16 13 3)
47 495: SEQUENCE { 47 495: SEQUENCE {
51 1: INTEGER 0 51 1: INTEGER 0
54 20: [0] 54 20: [0]
: 9E EB 67 C9 B9 5A 74 D4 4D 2F 16 39 66 80 E8 01 : 9E EB 67 C9 B9 5A 74 D4 4D 2F 16 39 66 80 E8 01
: B5 CB A4 9C : B5 CB A4 9C
76 9: SEQUENCE { 76 9: SEQUENCE {
78 7: OBJECT IDENTIFIER kemRSA (1 0 18033 2 2 4) 78 7: OBJECT IDENTIFIER kemRSA (1 0 18033 2 2 4)
: } : }
87 384: OCTET STRING 87 384: OCTET STRING
: C0 71 FC 27 3A F8 E7 BD B1 52 E0 6B F7 33 10 36 : C0 71 FC 27 3A F8 E7 BD B1 52 E0 6B F7 33 10 36
: 10 74 15 4A 43 AB CF 3C 93 C1 34 99 D2 06 53 44 : 10 74 15 4A 43 AB CF 3C 93 C1 34 99 D2 06 53 44
: 3E ED 9E F5 D3 C0 68 5E 4A A7 6A 68 54 81 5B B9 : 3E ED 9E F5 D3 C0 68 5E 4A A7 6A 68 54 81 5B B9
: 76 91 FF 9F 8D AC 15 EE A7 D7 4F 45 2B F3 50 A6 : 76 91 FF 9F 8D AC 15 EE A7 D7 4F 45 2B F3 50 A6
: 46 16 3D 68 28 8E 97 8C BF 7A 73 08 9E E5 27 12 : 46 16 3D 68 28 8E 97 8C BF 7A 73 08 9E E5 27 12
: F9 A4 F4 9E 06 AC E7 BB C8 5A B1 4D 4E 33 6C 97 : F9 A4 F4 9E 06 AC E7 BB C8 5A B1 4D 4E 33 6C 97
: C5 72 8A 26 54 13 8C 7B 26 E8 83 5C 6B 0A 9F BE : C5 72 8A 26 54 13 8C 7B 26 E8 83 5C 6B 0A 9F BE
: D2 64 95 C4 EA DF 74 5A 29 33 BE 28 3F 6A 88 B1 : D2 64 95 C4 EA DF 74 5A 29 33 BE 28 3F 6A 88 B1
: 66 95 FC 06 66 68 73 CF B6 D3 67 18 EF 33 76 CE : 66 95 FC 06 66 68 73 CF B6 D3 67 18 EF 33 76 CE
: FC 10 0C 39 41 F3 C4 94 94 40 78 32 58 07 A5 59 : FC 10 0C 39 41 F3 C4 94 94 40 78 32 58 07 A5 59
: 18 6B 95 CC AB F3 71 4C FA F7 9F 83 BD 30 53 7F : 18 6B 95 CC AB F3 71 4C FA F7 9F 83 BD 30 53 7F
: DD 9A ED 5A 4C DC BD 8B D0 48 6F AE D7 3E 9D 48 : DD 9A ED 5A 4C DC BD 8B D0 48 6F AE D7 3E 9D 48
: 6B 30 87 D6 C8 06 54 6B 6E 26 71 57 5C 98 46 1E : 6B 30 87 D6 C8 06 54 6B 6E 26 71 57 5C 98 46 1E
: 44 1F 65 54 2B D9 5D E2 6D 0F 53 A6 4E 78 48 D7 : 44 1F 65 54 2B D9 5D E2 6D 0F 53 A6 4E 78 48 D7
: 31 D9 60 8D 05 3E 8D 34 55 46 60 2D 86 23 6F FE : 31 D9 60 8D 05 3E 8D 34 55 46 60 2D 86 23 6F FE
: 37 04 C9 8A D5 91 44 F3 08 9E 5E 6D 52 7B 54 97 : 37 04 C9 8A D5 91 44 F3 08 9E 5E 6D 52 7B 54 97
: BA 10 3C 79 D6 2E 80 D0 23 54 10 B0 6F 71 A7 D9 : BA 10 3C 79 D6 2E 80 D0 23 54 10 B0 6F 71 A7 D9
: BD 1C 38 00 0F 91 0D 63 12 EA 2F 20 A3 55 75 35 : BD 1C 38 00 0F 91 0D 63 12 EA 2F 20 A3 55 75 35
: AD 01 B3 09 3F B5 F7 EE 50 70 80 D0 F7 7D 48 C9 : AD 01 B3 09 3F B5 F7 EE 50 70 80 D0 F7 7D 48 C9
: C3 B3 79 6F 6B 7D D3 78 60 85 FB 89 51 23 F0 4C : C3 B3 79 6F 6B 7D D3 78 60 85 FB 89 51 23 F0 4C
: A1 F1 C1 BE 22 C7 47 A8 DF AC E3 23 70 FB 0D 57 : A1 F1 C1 BE 22 C7 47 A8 DF AC E3 23 70 FB 0D 57
: 07 83 E2 7D BB 7E 74 FC A9 4E E3 96 76 FD E3 D8 : 07 83 E2 7D BB 7E 74 FC A9 4E E3 96 76 FD E3 D8
: A9 55 3D 87 82 24 73 6E 37 E1 91 DA B9 53 C7 E2 : A9 55 3D 87 82 24 73 6E 37 E1 91 DA B9 53 C7 E2
: 28 C0 7A D5 CA 31 22 42 1C 14 DE BD 07 2A 9A B6 : 28 C0 7A D5 CA 31 22 42 1C 14 DE BD 07 2A 9A B6
475 27: SEQUENCE { 475 27: SEQUENCE {
477 10: OBJECT IDENTIFIER 477 10: OBJECT IDENTIFIER
: kdf3 (1 3 133 16 840 9 44 1 2) : kdf3 (1 3 133 16 840 9 44 1 2)
489 13: SEQUENCE { 489 13: SEQUENCE {
491 9: OBJECT IDENTIFIER 491 9: OBJECT IDENTIFIER
: sha-256 (2 16 840 1 101 3 4 2 1) : sha-256 (2 16 840 1 101 3 4 2 1)
502 0: NULL 502 0: NULL
: } : }
: } : }
504 1: INTEGER 16 504 1: INTEGER 16
507 11: SEQUENCE { 507 11: SEQUENCE {
509 9: OBJECT IDENTIFIER 509 9: OBJECT IDENTIFIER
: aes128-wrap (2 16 840 1 101 3 4 1 5) : aes128-wrap (2 16 840 1 101 3 4 1 5)
: } : }
520 24: OCTET STRING 520 24: OCTET STRING
: 28 78 2E 5D 3D 79 4A 76 16 B8 63 FB CF C7 19 B7 : 28 78 2E 5D 3D 79 4A 76 16 B8 63 FB CF C7 19 B7
: 8F 12 DE 08 CF 28 6E 09 : 8F 12 DE 08 CF 28 6E 09
: } : }
: } : }
: } : }
546 60: SEQUENCE { 546 60: SEQUENCE {
548 9: OBJECT IDENTIFIER data (1 2 840 113549 1 7 1) 548 9: OBJECT IDENTIFIER data (1 2 840 113549 1 7 1)
559 29: SEQUENCE { 559 29: SEQUENCE {
561 9: OBJECT IDENTIFIER 561 9: OBJECT IDENTIFIER
: aes128-CBC (2 16 840 1 101 3 4 1 2) : aes128-CBC (2 16 840 1 101 3 4 1 2)
572 16: OCTET STRING 572 16: OCTET STRING
: 48 0C CA FE BA BE FA CE DB AD DE CA F8 88 77 81 : 48 0C CA FE BA BE FA CE DB AD DE CA F8 88 77 81
: } : }
590 16: [0] C6 CA 65 DB 7B DD 76 B0 F3 7E 2F AB 62 64 B6 6D 590 16: [0] C6 CA 65 DB 7B DD 76 B0 F3 7E 2F AB 62 64 B6 6D
: } : }
: } : }
: } : }
: } : }
D.3. Recipient RSA-KEM Decapsulate() Processing D.3. Recipient RSA-KEM Decapsulate() Processing
Bob's private key: Bob's private key:
-----BEGIN PRIVATE KEY----- -----BEGIN PRIVATE KEY-----
MIIG5AIBAAKCAYEA3ocW14cxncPJ47fnEjBZAyfC2lqapL3ET4jvV6C7gGeVrRQx MIIG5AIBAAKCAYEA3ocW14cxncPJ47fnEjBZAyfC2lqapL3ET4jvV6C7gGeVrRQx
WPDwl+cFYBBR2ej3j3/0ecDmu+XuVi2+s5JHKeeza+itfuhsz3yifgeEpeK8T+Su WPDwl+cFYBBR2ej3j3/0ecDmu+XuVi2+s5JHKeeza+itfuhsz3yifgeEpeK8T+Su
sHhn20/NBLhYKbh3kiAcCgQ56dpDrDvDcLqqvS3jg/VO+OPnZbofoHOOevt8Q/ro sHhn20/NBLhYKbh3kiAcCgQ56dpDrDvDcLqqvS3jg/VO+OPnZbofoHOOevt8Q/ro
ahJe1PlIyQ4udWB8zZezJ4mLLfbOA9YVaYXx2AHHZJevo3nmRnlgJXo6mE00E/6q ahJe1PlIyQ4udWB8zZezJ4mLLfbOA9YVaYXx2AHHZJevo3nmRnlgJXo6mE00E/6q
skipping to change at page 32, line 37 skipping to change at line 1477
Bob encodes the CMSORIforKEMOtherInfo structure with the algorithm Bob encodes the CMSORIforKEMOtherInfo structure with the algorithm
identifier for AES-128-KEYWRAP and a key length of 16 octets. The identifier for AES-128-KEYWRAP and a key length of 16 octets. The
DER encoding of CMSORIforKEMOtherInfo is not repeated here. DER encoding of CMSORIforKEMOtherInfo is not repeated here.
Bob derives the key-encryption key from shared secret and the Bob derives the key-encryption key from shared secret and the
CMSORIforKEMOtherInfo structure with KDF3 and SHA-256, the KEK is: CMSORIforKEMOtherInfo structure with KDF3 and SHA-256, the KEK is:
e6dc9d62ff2b469bef604c617b018718 e6dc9d62ff2b469bef604c617b018718
Bob uses AES-KEY-WRAP to decrypt the content-encryption key with the Bob uses AES-KEY-WRAP to decrypt the content-encryption key with the
key-encryption key; the content-encryption key is: key-encryption key. The content-encryption key is:
77f2a84640304be7bd42670a84a1258b 77f2a84640304be7bd42670a84a1258b
Bob decrypts the content using AES-128-CBC with the content- Bob decrypts the content using AES-128-CBC with the content-
encryption key. The 16-octet IV used is: encryption key. The 16-octet IV used is:
480ccafebabefacedbaddecaf8887781 480ccafebabefacedbaddecaf8887781
The received ciphertext content is: The received ciphertext content is:
skipping to change at page 33, line 29 skipping to change at line 1518
We thank Burt Kaliski, Alex Railean, Joe Mandel, Mike Ounsworth, We thank Burt Kaliski, Alex Railean, Joe Mandel, Mike Ounsworth,
Peter Campbell, Daniel Van Geest, and David Ireland for careful Peter Campbell, Daniel Van Geest, and David Ireland for careful
review and thoughtful comments that greatly improved this document. review and thoughtful comments that greatly improved this document.
Authors' Addresses Authors' Addresses
Russ Housley Russ Housley
Vigil Security, LLC Vigil Security, LLC
516 Dranesville Road 516 Dranesville Road
Herndon, VA, 20170 Herndon, VA 20170
United States of America United States of America
Email: housley@vigilsec.com Email: housley@vigilsec.com
Sean Turner Sean Turner
sn3rd sn3rd
Email: sean@sn3rd.com Email: sean@sn3rd.com
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