]>
Internet X.509 Public Key Infrastructure: Additional Algorithm Identifiers for RSASSA-PSS and ECDSA using SHAKEsCisco Systemspkampana@cisco.comNIST100 Bureau Drive, Stop 8930GaithersburgMD20899-8930USAquynh.dang@nist.gov
General
LAMPS WGDigital signatures are used to sign messages, X.509
certificates and CRLs (Certificate Revocation Lists). This
document describes the conventions for using the SHAKE function
family in Internet X.509 certificates and CRLs as one-way hash
functions with the RSA Probabilistic signature and
ECDSA signature algorithms. The conventions for the
associated subject public keys are also described.[ EDNOTE: Remove this section before publication. ]draft-ietf-lamps-pkix-shake-08:
Small nits from Russ while in WGLC.draft-ietf-lamps-pkix-shake-07:
Incorporated Eric's suggestion from WGLC.draft-ietf-lamps-pkix-shake-06:
Added informative references.Updated ASN.1 so it compiles.Updated IANA considerations.draft-ietf-lamps-pkix-shake-05:
Added RFC8174 reference and text.Explicitly explained why RSASSA-PSS-params are omitted in section 5.1.1.Simplified Public Keys section by removing redundand info from RFCs.draft-ietf-lamps-pkix-shake-04:
Removed paragraph suggesting KMAC to be used in generating k in Deterministric ECDSA. That should be RFC6979-bis. Removed paragraph from Security Considerations that talks about randomness of k because we are using deterministric ECDSA.Various ASN.1 fixes.Text fixes.draft-ietf-lamps-pkix-shake-03:
Updates based on suggestions and clarifications by Jim. Added ASN.1.draft-ietf-lamps-pkix-shake-02:
Significant reorganization of the sections to simplify the introduction, the new OIDs and their use in PKIX.Added new OIDs for RSASSA-PSS that hardcode hash, salt and MGF, according the WG consensus.Updated Public Key section to use the new RSASSA-PSS OIDs and clarify the algorithm identifier usage.Removed the no longer used SHAKE OIDs from section 3.1.Consolidated subsection for message digest algorithms.Text fixes.draft-ietf-lamps-pkix-shake-01:
Changed titles and section names.Removed DSA after WG discussions.Updated shake OID names and parameters, added MGF1 section.Updated RSASSA-PSS section.Added Public key algorithm OIDs.Populated Introduction and IANA sections.draft-ietf-lamps-pkix-shake-00:
Initial versionThis document describes cryptographic algorithm identifiers
for several cryptographic algorithms which use variable length output
SHAKE functions introduced in which can be used
with the Internet X.509 Certificate and CRL profile . 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 defined as SHAKE(M, d) where the
output is a d-bits long digest of message M. 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 as the message digest function (to hash the message to be signed)
in RSASSA-PSS and ECDSA and as the hash in the mask generating function in RSASSA-PSS.
This specification describes the identifiers for SHAKEs to be used in X.509 and their
meaning.The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in BCP 14
when, and only when, they appear in all capitals, as shown here.This section defines four new object identifiers (OIDs), for RSASSA-PSS and ECDSA with each
of SHAKE-128 and SHAKE-256. The same algorithm identifiers can be
used for identifying a public key in RSASSA-PSS.The new identifiers for RSASSA-PSS signatures using SHAKEs are below.The new algorithm identifiers of ECDSA signatures using SHAKEs are below.The parameters for the four identifiers above MUST be absent. That is,
the identifier SHALL be a SEQUENCE of one component, the OID. and specify the required output length
for each use of SHAKE128 or SHAKE256 in RSASSA-PSS and ECDSA. In summary, when hashing messages
to be signed, output lengths of SHAKE128 and SHAKE256 are 256 and 512 bits respectively.
When the SHAKEs are used as mask generation functions RSASSA-PSS, their output length is
(n - 264) or (n - 520) bits respectively, where n is the RSA modulus size in bits.Signatures are used in a number of different ASN.1 structures.
In an X.509 certificate a signature is encoded with an
algorithm identifier in the signatureAlgorithm attribute and
a signatureValue that contains the actual signature.
The identifiers defined in can be used
as the AlgorithmIdentifier in the signatureAlgorithm field in the sequence
Certificate and the signature field in the sequence tbsCertificate in X.509
.
The parameters of these signature algorithms are absent as explained
in .Conforming CA implementations MUST specify the algorithms
explicitly by using the OIDs specified in when
encoding RSASSA-PSS or ECDSA with SHAKE signatures
in certificates and CRLs.
Conforming client implementations that process RSASSA-PSS or ECDSA
with SHAKE signatures when processing certificates and CRLs
MUST recognize the corresponding OIDs.
Encoding rules for RSASSA-PSS and ECDSA
signature values are specified in and
respectively.The RSASSA-PSS algorithm is defined in .
When id-RSASSA-PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256 specified in
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.
defines RSASSA-PSS-params that are used to define the algorithms and inputs
to the algorithm. This specification does not use parameters because the
hash and mask generating algorithsm and trailer and salt are embedded in
the OID definition.The hash algorithm to hash a message being signed and the hash algorithm as the
mask generation function
used in RSASSA-PSS MUST be the same, SHAKE128 or SHAKE256 respectively. The
output-length of the hash algorithm which hashes the message SHALL be 32 or
64 bytes respectively. The 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 function, instead of the MGF1 algorithm that uses
the hash function in multiple iterations as specified in Section B.2.1 of
. In other words, the MGF is defined as
the SHAKE128 or SHAKE256 output of the mgfSeed for id-RSASSA-PSS-SHAKE128 and
id-RSASSA-PSS-SHAKE256 respectively. The mgfSeed is the seed
from which mask is generated, an octet string .
As explained in Step 9 of section 9.1.1 of , the output
length of the MGF is emLen - hLen - 1 bytes. emLen is the maximum message
length ceil((n-1)/8), where n is the RSA modulus in bits. hLen is 32 and
64-bytes for id-RSASSA-PSS-SHAKE128 and id-RSASSA-PSS-SHAKE256 respectively.
Thus when SHAKE is used as the MGF, the SHAKE output length maskLen is
(n - 264) or (n - 520) bits respectively. For example, when RSA modulus n is 2048,
the output length of SHAKE128 or SHAKE256 as the MGF will be 1784 or 1528-bits
when id-RSASSA-PSS-SHAKE128 or id-RSASSA-PSS-SHAKE256 is used respectively. 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 .The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined in
. When the id-ecdsa-with-SHAKE128 or id-ecdsa-with-SHAKE256
(specified in ) algorithm identifier appears, the respective SHAKE
function (SHAKE128 or SHAKE256) 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 length of the hash function must be explicitly determined. The
output length, d, for SHAKE128 or SHAKE256 used in ECDSA MUST be 256 or 512
bits respectively. It is RECOMMENDED that conforming CA implementations that generate ECDSA
with SHAKE signatures in certificates or CRLs generate such signatures
with a deterministically generated, non-random k in accordance
with all the requirements specified in .
They MAY also generate such signatures
in accordance with all other recommendations in or
if they have a stated policy that requires
conformance to these standards. These standards may have not specified
SHAKE128 and SHAKE256 as hash algorithm options. However, SHAKE128 and
SHAKE256 with output length being 32 and 64 octets respectively are
subtitutions for 256 and 512-bit output hash algorithms such as SHA256
and SHA512 used in the standards.Certificates conforming to can convey a
public key for any public key algorithm. The certificate indicates
the public key algorithm through an algorithm identifier. This algorithm
identifier is an OID and optionally associated parameters.
The conventions and encoding for RSASSA-PSS and ECDSA
public keys algorithm identifiers are as specified in
Section 2.3 of ,
Section 3.1 of
and Section 2.1 of .
Traditionally, the rsaEncryption object identifier is used to
identify RSA public keys. The rsaEncryption object identifier
continues to identify the subject public key when the RSA private
key owner does not wish to limit the use of the public key
exclusively to RSASSA-PSS with SHAKEs. When the RSA private
key owner wishes to limit the use of the public key exclusively
to RSASSA-PSS with SHAKEs, the AlgorithmIdentifiers for
RSASSA-PSS defined in SHOULD be used as the algorithm
field in the SubjectPublicKeyInfo sequence .
Conforming client implementations that process RSASSA-PSS
with SHAKE public keys when processing certificates and CRLs MUST
recognize the corresponding OIDs. Conforming CA implementations MUST specify the X.509 public key
algorithm explicitly by using the OIDs specified in
when encoding ECDSA with SHAKE public keys in certificates and CRLs.
Conforming client implementations that process ECDSA with
SHAKE public keys when processing certificates and CRLs MUST recognize
the corresponding OIDs. The identifier parameters, as explained in section ,
MUST be absent.One object identifier for the ASN.1 module in
was assigned in the SMI Security for PKIX Module Identifiers
(1.3.6.1.5.5.7.0) registry:
The SHAKEs are deterministic functions. Like any other deterministic function,
executing multiple times with the same input will produce the
same output. Therefore, users should not expect unrelated outputs (with the
same or different output lengths) from running a SHAKE function with the
same input multiple times. The shorter of any two 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.When using ECDSA with SHAKEs, the ECDSA curve order SHOULD be
chosen in line with the SHAKE output length. NIST has defined appropriate
use of the hash functions in terms of the algorithm strengths and
expected time frames for secure use in Special Publications (SPs)
and .
These documents can be used as guides to choose appropriate key sizes
for various security scenarios. In the context of this document
id-ecdsa-with-shake128 is RECOMMENDED for curves with group order
of 256-bits. id-ecdsa-with-shake256 is RECOMMENDED for curves
with group order of 384-bits or more.We would like to thank Sean Turner, Jim Schaad and Eric
Rescorla for their valuable contributions to this document.The authors would like to thank Russ Housley for his guidance and
very valuable contributions with the ASN.1 module.
&RFC2119;
&RFC8174;
&RFC4055;
&RFC5280;
&RFC5480;
&RFC8017;
SHA-3 Standard - Permutation-Based Hash and Extendable-Output Functions FIPS PUB 202National Institute of Standards and Technology (NIST)
&RFC3279;
&RFC5912;
&RFC6979;
SEC 1: Elliptic Curve CryptographyStandards for Efficient Cryptography GroupX9.62-2005: Public Key Cryptography for the Financial Services Industry: The Elliptic Curve Digital Signature Standard (ECDSA)American National Standard for Financial Services (ANSI)SP800-78-4: Cryptographic Algorithms and Key Sizes for Personal Identity VerificationNational Institute of Standards and Technology (NIST)SP800-107: Recommendation for Applications Using Approved Hash AlgorithmsNational Institute of Standards and Technology (NIST)This appendix includes the ASN.1 module for SHAKEs in X.509.
This module does not come from any existing RFC.