Network Working Group S. Josefsson
Internet-Draft SJD AB
Intended status: Informational N. Mavrogiannopoulos
Expires: March 26, 2016 Red Hat, Inc.
September 23, 2015
Using EdDSA in the Internet X.509 Public Key Infrastructure
draft-josefsson-pkix-eddsa-03
Abstract
This document specify algorithm identifiers and ASN.1 encoding
formats for EdDSA digital signatures and subject public keys used in
the Internet X.509 Public Key Infrastructure (PKIX) for Certificates
and CRLs. Parameters for Ed25519 are defined.
Status of This Memo
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This Internet-Draft will expire on March 26, 2016.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Terminology . . . . . . . . . . . . . . . . . . 2
3. Subject Public Key Information Fields . . . . . . . . . . . . 2
4. EdDSA Public Keys . . . . . . . . . . . . . . . . . . . . . . 3
5. Key Usage Bits . . . . . . . . . . . . . . . . . . . . . . . 4
6. EdDSA Signatures . . . . . . . . . . . . . . . . . . . . . . 4
7. Human Readable Algorithm Names . . . . . . . . . . . . . . . 5
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Example SHA512-Ed25519 Public Key . . . . . . . . . . . . 6
8.2. Example SHA512-Ed25519 Certificate . . . . . . . . . . . 6
8.3. Example SHA512-Ed25519 Private Key . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
11. Security Considerations . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
12.1. Normative References . . . . . . . . . . . . . . . . . . 9
12.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
In [Ed25519], an elliptic curve signature system EdDSA was
introduced, and a recommended choice of curve Ed25519 is chosen.
EdDSA and Ed25519 was designed with performance and security in mind.
Specification, test vectors and a sample implementation is available
in [I-D.josefsson-eddsa-ed25519].
This RFC defines ASN.1 object identifiers for EdDSA for use in the
Internet X.509 PKI [RFC5280], and parameters for Ed25519. This
document serves a similar role as [RFC3279] does for RSA (and more),
[RFC4055] for RSA-OAEP/PSS, and [RFC5758] for SHA2-based (EC)DSA.
2. Requirements Terminology
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].
3. Subject Public Key Information Fields
In the X.509 certificate, the subjectPublicKeyInfo field has the
SubjectPublicKeyInfo type, which has the following ASN.1 syntax:
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SubjectPublicKeyInfo ::= SEQUENCE {
algorithm AlgorithmIdentifier,
subjectPublicKey BIT STRING
}
The fields in SubjectPublicKeyInfo have the following meanings:
o algorithm is the algorithm identifier and parameters for the
public key (see below).
o subjectPublicKey is the EdDSA public key.
The AlgorithmIdentifier type, which is included for convenience, is
defined as follows:
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL
}
The fields in AlgorithmIdentifier have the following meanings:
o algorithm identifies the cryptographic algorithm with an object
identifier. This is the EdDSA OID defined below.
o parameters, which are optional, are the associated parameters for
the algorithm identifier in the algorithm field.
4. EdDSA Public Keys
Certificates conforming to [RFC5280] may convey a public key for any
public key algorithm. The certificate indicates the algorithm
through an algorithm identifier. This algorithm identifier is an OID
and optionally associated parameters.
This section identify the OID and parameters for the EdDSA algorithm.
Conforming CAs MUST use the identified OIDs when issuing certificates
containing EdDSA public keys. Conforming applications supporting
EdDSA MUST, at a minimum, recognize the OID identified in this
section.
The id-EdDSAPublicKey OID is used for identifying EdDSA public keys.
id-EdDSAPublicKey OBJECT IDENTIFIER ::= { 1.3.101.100 }
The id-EdDSAPublicKey OID is intended to be used in the algorithm
field of a value of type AlgorithmIdentifier.
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EdDSA public keys use the parameter field to specify the particular
instantiation of EdDSA parameters. The parameters field have the
ASN.1 type EdDSAParameters as follows.
EdDSAParameters ::= ENUMERATED { ed25519 (1),
sha512-ed25519 (2) }
The EdDSAParameters enumeration may be extended in the future.
The value 'ed25519' means the set of "pure" EdDSA parameters
associated with Ed25519, including internal hash function (SHA512)
and curve. The value 'sha512-ed25519' means that the SHA512
algorithm will be used as the prehash parameter and the hash function
for the signature. For the definitions see [EdDSA-prehash].
The raw binary EdDSA public key is encoded directly in the
subjectPublicKey BIT STRING object. Note that unlike some other
schemes, there is no additional OCTET STRING encoding step.
5. Key Usage Bits
The intended application for the key MAY be indicated in the keyUsage
certificate extension.
If the keyUsage extension is present in an end-entity certificate
that conveys an EdDSA public key with the id-EdDSAPublicKey object
identifier, then the keyUsage extension MUST contain one or both of
the following values:
nonRepudiation; and
digitalSignature.
If the keyUsage extension is present in a certification authority
certificate that conveys an EdDSA public key with the id-
EdDSAPublicKey object identifier, then the keyUsage extension MUST
contain one or more of the following values:
nonRepudiation;
digitalSignature;
keyCertSign; and
cRLSign.
6. EdDSA Signatures
Certificates and CRLs conforming to [RFC5280] may be signed with any
public key signature algorithm. The certificate or CRL indicates the
algorithm through an algorithm identifier which appears in the
signatureAlgorithm field within the Certificate or CertificateList.
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This algorithm identifier is an OID and has optionally associated
parameters. For illustration the Certificate structure is reproduced
here:
Certificate ::= SEQUENCE {
tbsCertificate TBSCertificate,
signatureAlgorithm AlgorithmIdentifier,
signatureValue BIT STRING }
Recall the definition of the AlgorithmIdentifier type:
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL
}
This document identify an AlgorithmIdentifier OID for EdDSA
signatures. No parameters are defined. The EdDSA parameters follow
from the public-key parameters.
The data to be signed is prepared for EdDSA. Then, a private key
operation is performed to generate the signature value. This value
is the opaque value ENC(R) || ENC'(S) described in section 4.3 of
[I-D.josefsson-eddsa-ed25519]. This signature value is then ASN.1
encoded as a BIT STRING and included in the Certificate or
CertificateList in the signatureValue field.
The id-EdDSASignature OID is used for identifying EdDSA signatures.
id-EdDSASignature OBJECT IDENTIFIER ::= { 1.3.101.101 }
The id-EdDSASignature OID is intended to be used in the algorithm
field of a value of type AlgorithmIdentifier. The parameters field
MUST be absent. To further clarify how to encode the parameters
field, due to historical misunderstandings in this area, it MUST NOT
have an ASN.1 type NULL.
7. Human Readable Algorithm Names
For the purpose of consistent cross-implementation naming this
section establish human readable names for the algorithms specified
in this document. Implementations SHOULD use these names when
referring to the algorithms. If there is a strong reason to deviate
from these names -- for example, if the implementation has a
different naming convention and wants to maintain internal
consistency -- it is encouraged to deviate as little as possible from
the names given here. For example, if a naming convention is to not
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use hyphen ("-") then instead of "SHA512-Ed25519" the string
"SHA512Ed25519" could be used.
Use the string "EdDSA" when referring to a public key or signature
when the parameter set is not known or relevant.
When the EdDSAParameters value is known, use a more specific string.
For the ed25519(1) value use the string "Ed25519". For the
sha512-ed25519(2) value use the string "SHA512-Ed25519".
8. Examples
This section contains illustrations of EdDSA public keys and
certificates, illustrating parameter choices.
8.1. Example SHA512-Ed25519 Public Key
An example of a SHA512-Ed25519 public key:
Public Key Information:
Public Key Algorithm: EdDSA
Algorithm Security Level: High (256 bits)
Parameters: SHA512-Ed25519
Public Key Usage:
Public Key ID: 9b1f5eeded043385e4f7bc623c5975b90bc8bb3b
-----BEGIN PUBLIC KEY-----
MC0wCAYDK2VkCgECAyEAGb9ECWmEzf6FQbrBZ9w7lshQhqowtrbLDFw4rXAxZuE=
-----END PUBLIC KEY-----
8.2. Example SHA512-Ed25519 Certificate
An example of a PKIX certificate using SHA512-Ed25519 would be:
X.509 Certificate Information:
Version: 3
Serial Number (hex): 5601474a2a8dc326
Issuer: CN=Test Ed25519-SHA512 certificate
Validity:
Not Before: Tue Sep 22 12:19:24 UTC 2015
Not After: Fri Dec 31 23:59:59 UTC 9999
Subject: CN=Test Ed25519-SHA512 certificate
Subject Public Key Algorithm: SHA512-EdDSA
Algorithm Security Level: High (256 bits)
Extensions:
Basic Constraints (critical):
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Certificate Authority (CA): FALSE
Key Usage (critical):
Digital signature.
Subject Key Identifier (not critical):
9b1f5eeded043385e4f7bc623c5975b90bc8bb3b
Signature Algorithm: SHA512-Ed25519
Signature:
be:9d:f8:b4:19:07:99:c9:04:12:21:e7:85:33:55:76
b0:5f:29:70:77:bd:69:7a:a6:db:33:fe:c4:f5:3d:79
d2:ba:77:6d:68:9b:a3:e9:53:bc:a6:56:54:3f:fa:f4
1c:37:89:4e:c7:43:c0:3b:77:68:5d:98:f6:19:9d:05
Other Information:
SHA1 fingerprint:
a3b75d83a56e127d0728ed8563233cadf943757e
SHA256 fingerprint:
cab1d7df29bdf82270d2192997c81f1b333dc37e670d7e88068fbe9dd747da3a
Public Key ID:
9b1f5eeded043385e4f7bc623c5975b90bc8bb3b
Public key's random art:
+-[SHA512Ed25519]-+
| . |
| o ..|
| o.=|
| . . +=|
| S o .+oo|
| o o.++o|
| o ...*.o.|
| o Eo.oo |
| ooo ..o|
+-----------------+
-----BEGIN CERTIFICATE-----
MIIBUTCCAQKgAwIBAgIIVgFHSiqNwyYwBgYEK2VkATAqMSgwJgYDVQQDEx9UZXN0
IEVkMjU1MTktU0hBNTEyIGNlcnRpZmljYXRlMCAXDTE1MDkyMjEyMTkyNFoYDzk5
OTkxMjMxMjM1OTU5WjAqMSgwJgYDVQQDEx9UZXN0IEVkMjU1MTktU0hBNTEyIGNl
cnRpZmljYXRlMC0wCAYDK2VkCgECAyEAGb9ECWmEzf6FQbrBZ9w7lshQhqowtrbL
DFw4rXAxZuGjQDA+MAwGA1UdEwEB/wQCMAAwDwYDVR0PAQH/BAUDAweAADAdBgNV
HQ4EFgQUmx9e7e0EM4Xk97xiPFl1uQvIuzswBgYEK2VkAQNBAL6d+LQZB5nJBBIh
54UzVXawXylwd71peqbbM/7E9T150rp3bWibo+lTvKZWVD/69Bw3iU7HQ8A7d2hd
mPYZnQU=
-----END CERTIFICATE-----
8.3. Example SHA512-Ed25519 Private Key
An example of a SHA512-Ed25519 private key:
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Public Key Info:
Public Key Algorithm: EdDSA
Key Security Level: High (256 bits)
parameters: SHA512-Ed25519
private key:
d4:ee:72:db:f9:13:58:4a:d5:b6:d8:f1:f7:69:f8:ad
3a:fe:7c:28:cb:f1:d4:fb:e0:97:a8:8f:44:75:58:42
x:
19:bf:44:09:69:84:cd:fe:85:41:ba:c1:67:dc:3b:96
c8:50:86:aa:30:b6:b6:cb:0c:5c:38:ad:70:31:66:e1
Public Key ID: 9B:1F:5E:ED:ED:04:33:85:E4:F7:BC:62:3C:59:75:B9:0B:C8:BB:3B
Public key's random art:
+-[SHA512Ed25519]-+
| . |
| o ..|
| o.=|
| . . +=|
| S o .+oo|
| o o.++o|
| o ...*.o.|
| o Eo.oo |
| ooo ..o|
+-----------------+
-----BEGIN EDDSA PRIVATE KEY-----
MCUKAQEEINTuctv5E1hK1bbY8fdp+K06/nwoy/HU++CXqI9EdVhC
-----END EdDSA PRIVATE KEY-----
9. Acknowledgements
Text and/or inspiration were drawn from [RFC5280], [RFC3279],
[RFC4055], [RFC5480], and [RFC5639].
The following people discussed the document and provided feedback:
Klaus Hartke, Ilari Liusvaara, Erwann Abalea, Rick Andrews, Rob
Stradling.
A big thank you to Symantec for kindly donating the OIDs used in this
draft.
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10. IANA Considerations
None.
11. Security Considerations
The security considerations of [RFC5280] and
[I-D.josefsson-eddsa-ed25519] apply accordingly.
A common misconception may be that a Ed25519 public key can be used
to create SHA512-Ed25519 signatures, or vice versa. This leads to
cross-key attacks, and is not permitted.
12. References
12.1. Normative References
[I-D.josefsson-eddsa-ed25519]
Josefsson, S. and N. Moller, "EdDSA and Ed25519", draft-
josefsson-eddsa-ed25519-02 (work in progress), February
2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
12.2. Informative References
[RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and
Identifiers for the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 3279, April 2002.
[RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional
Algorithms and Identifiers for RSA Cryptography for use in
the Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile", RFC 4055,
June 2005.
[RFC5480] Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
"Elliptic Curve Cryptography Subject Public Key
Information", RFC 5480, March 2009.
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[RFC5639] Lochter, M. and J. Merkle, "Elliptic Curve Cryptography
(ECC) Brainpool Standard Curves and Curve Generation", RFC
5639, March 2010.
[RFC5758] Dang, Q., Santesson, S., Moriarty, K., Brown, D., and T.
Polk, "Internet X.509 Public Key Infrastructure:
Additional Algorithms and Identifiers for DSA and ECDSA",
RFC 5758, January 2010.
[Ed25519] Bernstein, J., Duif, , Lange, , Schwabe, , and Yang,
"Ed25519: High-speed high-security signatures", WWW
http://ed25519.cr.yp.to/ed25519-20110926.pdf, September
2011.
[EdDSA-prehash]
Bernstein, J., Josefsson, , Lange, , Schwabe, , and Yang,
"EdDSA for more curves", WWW
http://ed25519.cr.yp.to/eddsa-20150704.pdf, July 2015.
Authors' Addresses
Simon Josefsson
SJD AB
Email: simon@josefsson.org
Nikos Mavrogiannopoulos
Red Hat, Inc.
Email: nmav@redhat.com
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