| LAMPS WG | Q. Dang |
| Internet-Draft | NIST |
| Intended status: Standards Track | P. Kampanakis |
| Expires: April 25, 2019 | Cisco Systems |
| October 22, 2018 |
Use of the SHAKE One-way Hash Functions in the Cryptographic Message Syntax (CMS)
draft-ietf-lamps-cms-shakes-02
This document describes the conventions for using the SHAKE family of hash functions with the Cryptographic Message Syntax (CMS).
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[ EDNOTE: Remove this section before publication. ]
The Cryptographic Message Syntax (CMS) [RFC5652] is used to digitally sign, digest, authenticate, or encrypt arbitrary message contents. This specification describes the use of the SHAKE128 and SHAKE256 specified in [SHA3] as new hash functions in CMS. In addition, it describes the use of these functions with the RSASSA-PSS signature algorithm [RFC8017] and the Elliptic Curve Digital Signature Algorithm (ECDSA) [X9.62] with the CMS signed-data content type.
The SHA-3 family of one-way hash functions is specified in [SHA3]. In the SHA-3 family, two extendable-output functions (SHAKEs): SHAKE128 and SHAKE256, are defined. Four other hash function instances, SHA3-224, SHA3-256, SHA3-384, and SHA3-512 are also defined but are out of scope for this document. A SHAKE is a variable length hash function. The output length, in bits, of a SHAKE is defined by the d parameter. The corresponding collision and second preimage resistance strengths for SHAKE128 are min(d/2,128) and min(d,128) bits respectively. And, the corresponding collision and second preimage resistance strengths for SHAKE256 are min(d/2,256) and min(d,256) bits respectively.
A SHAKE can be used in CMS as the message digest function (to hash the message to be signed) in RSASSA-PSS and deterministic ECDSA, message authentication code and as the mask generating function in RSASSA-PSS. In Section 3 of this document we define six new OIDs using SHAKE128 and SHAKE256 in CMS.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
The object identifiers for SHAKE128 and SHAKE256 hash functions are defined in [shake-nist-oids] and we include them here for convenience.
id-shake128-len OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) 2 17 }
id-shake256-len OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) 2 18 }
In this specification, when using the id-shake128-len or id-shake256-len algorithm identifiers, the parameters MUST be absent. That is, the identifier SHALL be a SEQUENCE of one component, the OID.
The new identifiers for RSASSA-PSS signatures using SHAKEs are below.
id-RSASSA-PSS-SHAKE128 OBJECT IDENTIFIER ::= { TBD }
id-RSASSA-PSS-SHAKE256 OBJECT IDENTIFIER ::= { TBD }
[ EDNOTE: "TBD" will be specified by NIST later. ]
The new algorithm identifiers of ECDSA signatures using SHAKEs are below.
id-ecdsa-with-SHAKE128 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) 3 TBD }
id-ecdsa-with-SHAKE256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) 3 TBD }
[ EDNOTE: "TBD" will be specified by NIST. ]
The same RSASSA-PSS and deterministric ECDSA with SHAKEs algorithm identifiers are used for identifying public keys and signatures.
The parameters for the four RSASSA-PSS and deterministic ECDSA identifiers MUST be absent. That is, each identifier SHALL be a SEQUENCE of one component, the OID.
The new object identifiers for KMACs using SHAKE128 and SHAKE256 are below.
id-KmacWithSHAKE128 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) 2 TBD }
id-KmacWithSHAKE256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1) gov(101) csor(3)
nistAlgorithm(4) 2 TBD }
EDNOTE: "TBD" will be specified by NIST.
The parameters for id-KmacWithSHAKE128 and id-KmacWithSHAKE256 MUST be absent. That is, each identifier SHALL be a SEQUENCE of one component, the OID.
Section 4.1, Section 4.2.1, Section 4.2.2 and Section 4.4 specify the required output length for each use of SHAKE128 or SHAKE256 in message digests, RSASSA-PSS, determinstic ECDSA and KMAC.
The id-shake128-len and id-shake256-len OIDs (Section 3) can be used as the digest algorithm identifiers located in the SignedData, SignerInfo, DigestedData, and the AuthenticatedData digestAlgorithm fields in CMS [RFC5652]. The encoding MUST omit the parameters field and the output size, d, for the SHAKE128 or SHAKE256 message digest MUST be 256 or 512 bits respectively.
The digest values are located in the DigestedData field and the Message Digest authenticated attribute included in the signedAttributes of the SignedData signerInfo. In addition, digest values are input to signature algorithms.
In CMS, signature algorithm identifiers are located in the SignerInfo signatureAlgorithm field of SignedData content type and countersignature attribute. Signature values are located in the SignerInfo signature field of SignedData and countersignature.
Conforming implementations that process RSASSA-PSS and deterministic ECDSA with SHAKE signatures when processing CMS data MUST recognize the corresponding OIDs specified in Section 3.
The RSASSA-PSS algorithm is defined in [RFC8017]. When id-RSASSA-PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256 specified in Section 3 is used, the encoding MUST omit the parameters field. That is, the AlgorithmIdentifier SHALL be a SEQUENCE of one component, id-RSASSA-PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256.
The hash algorithm to hash a message being signed and the hash algorithm as the mask generation function "MGF(H, emLen - hLen - 1)" [RFC8017] used in RSASSA-PSS MUST be the same, SHAKE128 or SHAKE256 respectively. The output-length of the SHAKE which hashes the message SHALL be 32 or 64 bytes respectively.
SHAKE128(mgfSeed, maskLen)
SHA256(mgfSeed, maskLen)
In RSASSA-PSS, a mask generation function takes an octet string of variable length and a desired output length as input, and outputs an octet string of the desired length. In RSASSA-PSS with SHAKES, the SHAKEs MUST be used natively as the MGF, instead of the MGF1 algorithm that uses the hash function in multiple iterations as specified in Section B.2.1 of [RFC8017]. In other words, the MGF is defined as
The RSASSA-PSS saltLength MUST be 32 or 64 bytes respectively. Finally, the trailerField MUST be 1, which represents the trailer field with hexadecimal value 0xBC [RFC8017].
The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined in [X9.62]. When the id-ecdsa-with-SHAKE128 or id-ecdsa-with-SHAKE256 (specified in Section 3) algorithm identifier appears, the respective SHAKE function is used as the hash. The encoding MUST omit the parameters field. That is, the AlgorithmIdentifier SHALL be a SEQUENCE of one component, the OID id-ecdsa-with-SHAKE128 or id-ecdsa-with-SHAKE256.
For simplicity and compliance with the ECDSA standard specification, the output size of the hash function must be explicitly determined. The output size, d, for SHAKE128 or SHAKE256 used in ECDSA MUST be 256 or 512 bits respectively. The ECDSA message hash function is SHAKE128 or SHAKE256 respectively.
Conforming implementations that generate ECDSA with SHAKE signatures in CMS MUST generate such signatures with a deterministicly generated, non-random k in accordance with all the requirements specified in [RFC6979]. They MAY also generate such signatures in accordance with all other recommendations in [X9.62] or [SEC1] if they have a stated policy that requires conformance to these standards.
In Section 3.2 "Generation of k" of [RFC6979], HMAC is used to derive the deterministic k. Conforming implementations that generate deterministic ECDSA with SHAKE signatures in X.509 MUST use KMAC with SHAKE128 or KMAC with SHAKE256 as specfied in [SP800-185] when SHAKE128 or SHAKE256 is used as the message hashing algorithm, respectively. In this situation, KMAC with SHAKE128 and KMAC with SHAKE256 have 256-bit and 512-bit outputs respectively, and the optional customization bit string S is an empty string.
In CMS, the signer's public key algorithm identifiers are located in the OriginatorPublicKey's algorithm attribute.
Conforming implementations MUST specify the algorithms explicitly by using the OIDs specified in Section 3 when encoding RSASSA-PSS and ECDSA with SHAKE public keys in CMS messages. The conventions for RSASSA-PSS and ECDSA public keys algorithm identifiers are as specified in [RFC3279], [RFC4055] and [RFC5480] , but we include them below for convenience.
[RFC3279] defines the following OID for RSA AlgorithmIdentifier in the SubjectPublicKeyInfo with NULL parameters.
rsaEncryption OBJECT IDENTIFIER ::= { pkcs-1 1}
Additionally, when the RSA private key owner wishes to limit the use of the public key exclusively to RSASSA-PSS, the AlgorithmIdentifier for RSASSA-PSS defined in Section 3 can be used as the algorithm attribute in the OriginatorPublicKey sequence. The identifier parameters, as explained in Section 3, MUST be absent. The RSASSA-PSS algorithm functions and output lengths are the same as defined in Section 4.2.1.
Regardless of what public key algorithm identifier is used, the RSA public key, which is composed of a modulus and a public exponent, MUST be encoded using the RSAPublicKey type [RFC4055]. The output of this encoding is carried in the CMS publicKey bit string.
RSAPublicKey ::= SEQUENCE {
modulus INTEGER, -- n
publicExponent INTEGER -- e
}
When id-ecdsa-with-shake128 or id-ecdsa-with-shake256 are used as the algorithm identitifier in the public key, the parameters, as explained in Section 3, MUST be absent. The hash function and its output-length are the same as in Section 4.2.2.
Additionally, the mandatory EC SubjectPublicKey is defined in Section 2.1.1 and its syntax in Section 2.2 of [RFC5480]. We also include them here for convenience:
id-ecPublicKey OBJECT IDENTIFIER ::= {
iso(1) member-body(2) us(840) ansi-X9-62(10045) keyType(2) 1 }
ECParameters ::= CHOICE {
namedCurve OBJECT IDENTIFIER
-- implicitCurve NULL
-- specifiedCurve SpecifiedECDomain
}
The ECParameters associated with the ECDSA public key in the signers certificate SHALL apply to the verification of the signature.
KMAC message authentication code (KMAC) is specified in [SP800-185]. In CMS, KMAC algorithm identifiers are located in the AuthenticatedData macAlgorithm field. The KMAC values are located in the AuthenticatedData mac field.
When the id-KmacWithSHAKE128 or id-KmacWithSHAKE256 algorithm identifier is used as the KMAC algorithm identifier, the parameters field MUST be absent.
Conforming implementations that process KMACs with the SHAKEs when processing CMS data MUST recognize these identifiers.
When calculating the KMAC output, the variable N is 0xD2B282C2, S is an empty string, and L, the integer representing the requested output length in bits, is 256 or 512 for KmacWithSHAKE128 or KmacWithSHAKE256 respectively in this specification.
[ EDNOTE: Update here only if there are OID allocations by IANA. ]
This document has no IANA actions.
SHAKE128 and SHAKE256 are one-way extensible-output functions. Their output length depends on a required length of the consuming application.
The SHAKEs are deterministic functions. Like any other deterministic functions, executing each function with the same input multiple times will produce the same output. Therefore, users should not expect unrelated outputs (with the same or different output lengths) from excuting a SHAKE function with the same input multiple times. The shorter one of any 2 outputs produced from a SHAKE with the same input is a prefix of the longer one. It is a similar situation as truncating a 512-bit output of SHA-512 by taking its 256 left-most bits. These 256 left-most bits are a prefix of the 512-bit output.
Implementations must protect the signer's private key. Compromise of the signer's private key permits masquerade.
When more than two parties share the same message-authentication key, data origin authentication is not provided. Any party that knows the message-authentication key can compute a valid MAC, therefore the content could originate from any one of the parties.
Implementations must randomly generate message-authentication keys and one-time values, such as the k value when generating a ECDSA signature. In addition, the generation of public/private key pairs relies on random numbers. The use of inadequate pseudo-random number generators (PRNGs) to generate such cryptographic values can result in little or no security. The generation of quality random numbers is difficult. [RFC4086] offers important guidance in this area, and [SP800-90A] series provide acceptable PRNGs.
Implementers should be aware that cryptographic algorithms may become weaker with time. As new cryptanalysis techniques are developed and computing power increases, the work factor or time required to break a particular cryptographic algorithm may decrease. Therefore, cryptographic algorithm implementations should be modular allowing new algorithms to be readily inserted. That is, implementers should be prepared to regularly update the set of algorithms in their implementations.
This document is based on Russ Housley's draft [I-D.housley-lamps-cms-sha3-hash] It replaces SHA3 hash functions by SHAKE128 and SHAKE256 as the LAMPS WG agreed.
[EDNOTE: Update. TBD. ]
PKIXAlgsForSHAKE-2018 { iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-cms-shakes-2018(TBD) }
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
-- EXPORTS ALL;
IMPORTS
-- FROM [RFC6268]
--
-- One-Way Hash Functions
-- SHAKE128
mda-shake128 DIGEST-ALGORITHM ::= {
IDENTIFIER id-shake128 -- with output length 32 bytes.
}
id-shake128 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16)
us(840) organization(1) gov(101)
csor(3) nistAlgorithm(4)
hashAlgs(2) 11 }
-- SHAKE-256
mda-shake256 DIGEST-ALGORITHM ::= {
IDENTIFIER id-shake256 -- with output length 64 bytes.
}
id-shake256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16)
us(840) organization(1) gov(101)
csor(3) nistAlgorithm(4)
hashAlgs(2) 12 }
--
-- KMAC Functions
-- KMAC with SHAKE128
KMACwithSHAKE128 MAC-ALGORITHM ::= {
IDENTIFIER id-KMACWithSHAKE128
PARAMS TYPE KMACwithSHAKE128-params ARE required
}
id-KMACWithSHAKE128 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1)
gov(101) csor(3) nistAlgorithm(4)
hashAlgs(2) 19 }
KMACwithSHAKE128-params ::= SEQUENCE {
KMACOutputLength INTEGER DEFAULT 256, -- Output length in bits
customizationString OCTET STRING DEFAULT ''
}
-- KMAC with SHAKE256
KMACwithSHAKE256 MAC-ALGORITHM ::= {
IDENTIFIER id-KMACWithSHAKE256
PARAMS TYPE KMACwithSHAKE256-params ARE required
}
id-KMACWithSHAKE256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2)
country(16) us(840) organization(1)
gov(101) csor(3) nistAlgorithm(4)
hashAlgs(2) 20 }
KMACwithSHAKE256-params ::= SEQUENCE {
KMACOutputLength INTEGER DEFAULT 512, -- Output length in bits
customizationString OCTET STRING DEFAULT ''
}
END