Internet DRAFT - draft-josefsson-tls-ed25519
draft-josefsson-tls-ed25519
Network Working Group S. Josefsson
Internet-Draft SJD AB
Intended status: Informational May 30, 2015
Expires: December 1, 2015
Using EdDSA/Ed25519 in the Internet X.509 Public Key Infrastructure
draft-josefsson-tls-ed25519-00
Abstract
This document specify algorithm identifiers and ASN.1 encoding
formats for EdDSA/Ed25519 digital signatures and subject public keys
used in the Internet X.509 Public Key Infrastructure (PKIX) for
Certificates and CRLs.
Status of This Memo
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This Internet-Draft will expire on December 1, 2015.
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1. Introduction
In [Ed25519], an elliptic curve signature system EdDSA was
introduced, and a recommended choice of curve Ed25519 is chosen.
Ed25519 was designed with performance and security in mind. EdDSA
and Ed25519 is also described in [I-D.josefsson-eddsa-ed25519].
This RFC defines ASN.1 object identifiers for EdDSA and Ed25519 for
use in the Internet X.509 PKI [RFC5280]. 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. EdDSA ASN.1 Object Identifier Tree
The root of the tree for the object identifiers defined in this
specification is given by:
id-EdDSA OBJECT IDENTIFIER ::= { 1.3.6.1.4.1.11591.4.12 }
4. Subject Public Key Information Fields
In the X.509 certificate, the subjectPublicKeyInfo field has the
SubjectPublicKeyInfo type, which has the following ASN.1 syntax:
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:
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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.
5. 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 ::= { id-EdDSA 1 }
The id-EdDSAPublicKey OID is intended to be used in the algorithm
field of a value of type AlgorithmIdentifier. The parameters field
MUST have ASN.1 type NULL for this algorithm identifier.
The EdDSA public key MUST be encoded using the ASN.1 type
EdDSAPublicKey:
EdDSAPublicKey ::= OCTET STRING -- LE edwards point
where the value is the little-endian encoded edwards point. The DER
encoded EdDSAPublicKey is the value of the BIT STRING
subjectPublicKey.
6. Key Usage Bits
The intended application for the key MAY be indicated in the keyUsage
certificate extension.
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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.
7. 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.
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 }
Also 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 data to be signed is prepared for EdDSA. Then, a private key
operation is performed to generate the signature value. This
signature value is then ASN.1 encoded as a BIT STRING and included in
the Certificate or CertificateList in the signature field.
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The id-EdDSASignature OID is used for identifying EdDSA signatures.
id-EdDSASignature OBJECT IDENTIFIER ::= { id-EdDSA 2 }
The id-EdDSASignature OID is intended to be used in the algorithm
field of a value of type AlgorithmIdentifier. The parameters field
MUST have ASN.1 type NULL for this algorithm identifier.
8. Acknowledgements
Text and/or inspiration were drawn from [RFC5280], [RFC3279],
[RFC4055], [RFC5480], and [RFC5639].
Thanks to Ilari Liusvaara for ideas and discussion.
9. IANA Considerations
None.
10. Security Considerations
The security considerations of [RFC5280] and
[I-D.josefsson-eddsa-ed25519] apply accordingly.
11. References
11.1. 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.
11.2. 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.
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[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.
[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.
Author's Address
Simon Josefsson
SJD AB
Email: simon@josefsson.org
Josefsson Expires December 1, 2015 [Page 6]
