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Versions: (draft-ietf-curdle-pkix-newcurves) 00 01 02 03 04 05 06 07 08 09 10 RFC 8410

Network Working Group                                       S. Josefsson
Internet-Draft                                                    SJD AB
Intended status: Standards Track                               J. Schaad
Expires: May 4, 2017                                      August Cellars
                                                        October 31, 2016


Algorithm Identifiers for Ed25519, Ed25519ph, Ed448, Ed448ph, X25519 and
      X448 for use in the Internet X.509 Public Key Infrastructure
                       draft-ietf-curdle-pkix-02

Abstract

   This document specifies algorithm identifiers and ASN.1 encoding
   formats for Elliptic Curve constructs using the Curve25519 and
   Curve448 curves.  The signature algorithms covered are Ed25519,
   Ed25519ph, Ed448 and Ed448ph.  The key agreement algorithm covered
   are X25519 and X448.  The Encoding for Public Key, Private Key and
   EdDSA digital signature structures is provided.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 4, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Terminology  . . . . . . . . . . . . . . . . . .   3
   3.  Curve25519 and Curve448 Algorithm Identifiers . . . . . . . .   3
   4.  Subject Public Key Fields . . . . . . . . . . . . . . . . . .   4
   5.  Key Usage Bits  . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  EdDSA Signatures  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Private Key Format  . . . . . . . . . . . . . . . . . . . . .   6
   8.  Human Readable Algorithm Names  . . . . . . . . . . . . . . .   7
   9.  ASN.1 Module  . . . . . . . . . . . . . . . . . . . . . . . .   8
   10. Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Example Ed25519 Public Key . . . . . . . . . . . . . . .  10
     10.2.  Example X25519 Certificate . . . . . . . . . . . . . . .  11
     10.3.  Example Ed25519 Private Key  . . . . . . . . . . . . . .  13
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  14
     14.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   In [RFC7748], the elliptic curves Curve25519 and Curve448 are
   described.  They are designed with performance and security in mind.
   The curves may be used for Diffie-Hellman and Digital Signature
   operations.

   [RFC7748] describes the operations on these curves for the Diffie-
   Hellman operation.  A convention has developed that when these two
   curves are used with the Diffie-Hellman operation, they are referred
   to as X25519 and X448.  This RFC defines the ASN.1 Object Identifiers
   (OIDs) for the operations X25519 and X448 along with the parameters.
   The use of these OIDs is described for public and private keys.

   In [I-D.irtf-cfrg-eddsa] the elliptic curve signature system Edwards-
   curve Digital Signature Algorithm (EdDSA) is described along with a
   recommendation for the use of the Curve25519 and Curve448.  EdDSA has
   defined two modes, the PureEdDSA mode without pre-hashing, and the
   HashEdDSA mode with pre-hashing.  The Ed25519ph and Ed448ph algorithm
   definitions specify the one-way hash function that is used for pre-
   hashing.  The convention used for identifying the algorithm/curve



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   combinations are to use the Ed25519 and Ed448 for the PureEdDSA mode,
   with Ed25519ph and Ed448ph for the HashEdDSA mode.  The use of the
   OIDs is described for public keys, private keys and signatures.

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.  Curve25519 and Curve448 Algorithm Identifiers

   Certificates conforming to [RFC5280] can 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.

   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 one of the OIDs defined below.

   o  parameters, which are optional, are the associated parameters for
      the algorithm identifier in the algorithm field.  When the 1997
      syntax for AlgorithmIdentifier was initially defined, it omitted
      the OPTIONAL key word.  The optionality of the parameters field
      was later recovered via a defect report, but by then many people
      thought that the field was mandatory.  For this reason, a small
      number of implementations may still require the field to be
      present.

   In this document we defined six new OIDs for identifying the
   different curve/algorithm pairs.  The curves being Curve25519 and
   Curve448.  The algorithms being ECDH, EdDSA in pure mode and EdDSA in
   pre-hash mode.  For all of the OIDs, the parameters MUST be absent.
   Implementations SHOULD NOT accept a parameters value of NULL.

   The same algorithm identifiers are used for identifying a public key,
   identifying a private key and identifying a signature (for the four




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   EdDSA related OIDs).  Additional encoding information is provided
   below for each of these locations.

   id-X25519    OBJECT IDENTIFIER ::= { 1 3 101 110 }
   id-X448      OBJECT IDENTIFIER ::= { 1 3 101 111 }
   id-Ed25519   OBJECT IDENTIFIER ::= { 1 3 101 112 }
   id-Ed448     OBJECT IDENTIFIER ::= { 1 3 101 113 }
   id-Ed25519ph OBJECT IDENTIFIER ::= { 1 3 101 114 }
   id-Ed448ph   OBJECT IDENTIFIER ::= { 1 3 101 115 }

4.  Subject Public Key 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 above).

   o  subjectPublicKey contains the byte stream of the public key.
      While the encoded public keys for the current algorithms are all
      an even number of octets, future curves could change that.

   Both [RFC7748] and [I-D.irtf-cfrg-eddsa] define the public key value
   as being a byte string.  It should be noted that the public key is
   computed differently for each of these documents, thus the same
   private key will not produce the same public key.

   The following is an example of a public key encoded using the textual
   encoding defined in [RFC7468].

   -----BEGIN PUBLIC KEY-----
   MCowBQYDK2VwAyEAGb9ECWmEzf6FQbrBZ9w7lshQhqowtrbLDFw4rXAxZmE=
   -----END PUBLIC KEY-----

5.  Key Usage Bits

   The intended application for the key is indicated in the keyUsage
   certificate extension.






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   If the keyUsage extension is present in a certificate that indicates
   id-X25119 or id-X448 in SubjectPublicKeyInfo, then the following MUST
   be present:

           keyAgreement;

   one of the following MAY also be present:

             encipherOnly; or
             decipherOnly.

   If the keyUsage extension is present in an end-entity certificate
   that indicates id-EdDSA25519, id-EdDSA25519ph, id-EdDSA448 or id-
   EdDSA448ph , 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 indicates id-EdDSA25519 or id-EdDSA448, then the
   keyUsage extension MUST contain one or more of the following values:

          nonRepudiation;
          digitalSignature;
          keyCertSign; and
          cRLSign.

   CAs MUST NOT use the pre-hash versions of the EdDSA algorithms for
   the creation of certificates or CRLs.  This is implied by the fact
   that those algorithms are not listed in the previous paragraph.
   Additionally OCSP responders SHOULD NOT use the pre-hash versions of
   the EdDSA algorithms when generating OCSP responses.  No restriction
   is placed on generation of OCSP requests.

   AAs MUST NOT use the pre-hash versions of the EdDSA algorithms for
   the creation of attribute certificates or attribute CRLs [RFC5755].

6.  EdDSA Signatures

   Signatures can be placed in a number of different ASN.1 structures.
   The top level structure for a certificate is given below as being
   illustrative of how signatures are frequently encoded with an
   algorithm identifier and a location for the signature.







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      Certificate  ::=  SEQUENCE  {
           tbsCertificate       TBSCertificate,
           signatureAlgorithm   AlgorithmIdentifier,
           signatureValue       BIT STRING  }

   The same algorithm identifiers are used for signatures as are used
   for public keys.  When used to identify signature algorithms, the
   parameters MUST be absent.

   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 3.3 of
   [I-D.irtf-cfrg-eddsa].  The octet string representing the signature
   is encoded directly in the BIT STRING without adding any additional
   ASN.1 wrapping.  For the Certificate structure, the signature value
   is wrapped in the 'signatureValue' BIT STRING field.

   When the pre-hash versions of the EdDSA signature algorithms are
   used, the hash function used for the pre-hash is defined by the
   algorithm.  This means that the pre-hash function is implicitly
   included in the algorithm identifier rather than being explicit as
   done in [RFC3279].

   In [I-D.irtf-cfrg-eddsa], a parameter was defined for a context
   value, specific to an application, to be provided to the signing
   operation.  This value is used to force different signatures to be
   generated for different applications.  Along with the defintion of
   the context comes a recommendation that contexts only be used if all
   of the signature algorithms used for an application have the ability
   to accept a context string.  For this reason, applications MUST NOT
   define the use a context value with the signatures created for these
   OIDs.  New OIDs would be defined in the event that context values
   appear to provide additional value.

7.  Private Key Format

   Asymmetric Key Packages [RFC5958] describes how encode a private key
   in a structure that both identifies what algorithm the private key is
   for, but allows for the public key and additional attributes about
   the key to be included as well.  For illustration, the ASN.1
   structure OneAsymmetricKey is replicated below.  The algorithm
   specific details of how a private key is encoded is left for the
   document describing the algorithm itself.








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   OneAsymmetricKey ::= SEQUENCE {
      version Version,
      privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
      privateKey PrivateKey,
      attributes [0] Attributes OPTIONAL,
      ...,
      [[2: publicKey [1] PublicKey OPTIONAL ]],
      ...
   }

   PrivateKey ::= OCTET STRING

   PublicKey ::= OCTET STRING

   For the keys defined in this document, the private key is always an
   opaque byte sequence.  The ASN.1 type EdPrivateKey is defined in this
   document to hold the byte sequence.  Thus when encoding a
   OneAsymmetricKey object, the private key is wrapped in an
   EdPrivateKey object and then placed in the 'privateKey' field.

   EdPrivateKey ::= OCTET STRING

   To encode a EdDSA, X25519 or X448 private key, the "privateKey" field
   will hold the encoded private key.  The "privateKeyAlgorithm" field
   uses the AlgorithmIdentifier structure.  The structure is encoded as
   defined above.  If present, the "publicKey" field will hold the
   encoded key as defined in [RFC7748] and [I-D.irtf-cfrg-eddsa].
   public key.

   The following is an example of a private key encoded using the
   textual encoding defined in [RFC7468].

   -----BEGIN PRIVATE KEY-----
   MC4CAQAwBQYDK2VwBCIEINTuctv5E1hK1bbY8fdp+K06/nwoy/HU++CXqI9EdVhC
   -----END PRIVATE KEY-----

8.  Human Readable Algorithm Names

   For the purpose of consistent cross-implementation naming this
   section establishes 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.





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   Use the string "ECDH" when referring to a public key of type X25519
   or X448 when the curve is not known or relevant.

   When the curve is known, use the more specific string of X25519 or
   X448.

   Use the string "EdDSA" when referring to a signing public key or
   signature when the curve is not known or relevant.

   When the curve is known, use a more specific string.  For the id-
   EdDSA25519 value use the string "Ed25519".  For the id-EdDSA25519ph
   value use the string "Ed25519ph".  For id-EdDSA448 use "Ed448".  For
   id-EdDSA448ph use "Ed448ph".

9.  ASN.1 Module

   For reference purposes, the ASN.1 syntax is presented as an ASN.1
   module here.

   -- ASN.1 Module

   Safecurves-pkix-0 {1 3 101 120}

   DEFINITIONS EXPLICIT TAGS ::=
   BEGIN

   IMPORTS
     SIGNATURE-ALGORITHM, KEY-AGREE, PUBLIC-KEY, KEY-WRAP,
     KeyUsage, AlgorithmIdentifier
     FROM AlgorithmInformation-2009
       {iso(1) identified-organization(3) dod(6) internet(1) security(5)
       mechanisms(5) pkix(7) id-mod(0)
       id-mod-algorithmInformation-02(58)}

     mda-sha512
     FROM PKIX1-PSS-OAEP-Algorithms-2009
       { iso(1) identified-organization(3) dod(6) internet(1)
         security(5) mechanisms(5) pkix(7) id-mod(0)
         id-mod-pkix1-rsa-pkalgs-02(54) }

     kwa-aes128-wrap, kwa-aes256-wrap
     FROM CMSAesRsaesOaep-2009
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
         smime(16) modules(0) id-mod-cms-aes-02(38) }
     ;


   id-edwards-curve-algs OBJECT IDENTIFIER ::= { 1 3 101 }



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   id-X25519        OBJECT IDENTIFIER ::= { id-edwards-curve-algs 110 }
   id-X448          OBJECT IDENTIFIER ::= { id-edwards-curve-algs 111 }
   id-EdDSA25519    OBJECT IDENTIFIER ::= { id-edwards-curve-algs 112 }
   id-EdDSA25519-ph OBJECT IDENTIFIER ::= { id-edwards-curve-algs 114 }
   id-EdDSA448      OBJECT IDENTIFIER ::= { id-edwards-curve-algs 113 }
   id-EdDSA448-ph   OBJECT IDENTIFIER ::= { id-edwards-curve-algs 115 }


    sa-EdDSA25519 SIGNATURE-ALGORITHM ::= {
       IDENTIFIER id-EdDSA25519
        PARAMS ARE absent
        PUBLIC-KEYS {pk-EdDSA25519}
        SMIME-CAPS { IDENTIFIED BY id-EdDSA25519 }
    }

    pk-EdDSA25519 PUBLIC-KEY ::= {
        IDENTIFIER id-EdDSA25519
        -- KEY no ASN.1 wrapping --
        PARAMS ARE absent
        CERT-KEY-USAGE {digitalSignature, nonRepudiation,
                        keyCertSign, cRLSign}
        PRIVATE-KEY EdPrivateKey
    }

    sa-EdDSA25519-ph SIGNATURE-ALGORITHM ::= {
        IDENTIFIER id-EdDSA25519-ph
        PARAMS ARE absent
        HASHES { mda-sha512 }
        PUBLIC-KEYS {pk-EdDSA25519-ph}
        SMIME-CAPS { IDENTIFIED BY id-EdDSA25519-ph }
    }

    pk-EdDSA25519-ph PUBLIC-KEY ::= {
        IDENTIFIER id-EdDSA25519-ph
        -- KEY no ASN.1 wrapping --
        PARAMS ARE absent
        CERT-KEY-USAGE {digitalSignature, nonRepudiation}
        PRIVATE-KEY EdPrivateKey
    }

    kaa-X25519 KEY-AGREE ::= {
        IDENTIFIER id-X25519
        PARAMS ARE absent
        PUBLIC-KEYS {pk-X25519}
        UKM -- TYPE no ASN.1 wrapping -- ARE preferredPresent
        SMIME-CAPS {
           TYPE AlgorithmIdentifier{KEY-WRAP, {KeyWrapAlgorithms}}
           IDENTIFIED BY id-X25519 }



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    }

    pk-X25519 PUBLIC-KEY ::= {
        IDENTIFIER id-X25519
        -- KEY no ASN.1 wrapping --
        PARAMS ARE absent
        CERT-KEY-USAGE { keyAgreement }
        PRIVATE-KEY EdPrivateKey
    }

    KeyWrapAlgorithms KEY-WRAP ::= {
        kwa-aes128-wrap | kwa-aes256-wrap,
        ...
    }

    kaa-X488 KEY-AGREE ::= {
        IDENTIFIER id-X448
        PARAMS ARE absent
        PUBLIC-KEYS {pk-X448}
        UKM -- TYPE no ASN.1 wrapping  -- ARE preferredPresent
        SMIME-CAPS {
           TYPE AlgorithmIdentifier{KEY-WRAP, {KeyWrapAlgorithms}}
           IDENTIFIED BY id-X448 }
    }

    pk-X448 PUBLIC-KEY ::= {
        IDENTIFIER id-X448
        -- KEY no ASN.1 wrapping --
        PARAMS ARE absent
        CERT-KEY-USAGE { keyAgreement }
        PRIVATE-KEY EdPrivateKey
    }

   EdPrivateKey ::= OCTET STRING


   END

10.  Examples

   This section contains illustrations of EdDSA public keys and
   certificates, illustrating parameter choices.

10.1.  Example Ed25519 Public Key

   An example of a Ed25519 public key:





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         Public Key Information:
             Public Key Algorithm: EdDSA25519
             Algorithm Security Level: High

         Public Key Usage:

         Public Key ID: 9b1f5eeded043385e4f7bc623c5975b90bc8bb3b

         -----BEGIN PUBLIC KEY-----
         MCowBQYDK2VwAyEAGb9ECWmEzf6FQbrBZ9w7lshQhqowtrbLDFw4rXAxZmE=
         -----END PUBLIC KEY-----

10.2.  Example X25519 Certificate

   An example of a self issued PKIX certificate using Ed25519 to sign a
   X25519 public key would be:

    0 300: SEQUENCE {
    4 223:   SEQUENCE {
    7   3:     [0] {
    9   1:       INTEGER 2
         :       }
   12   8:     INTEGER 56 01 47 4A 2A 8D C3 30
   22   5:     SEQUENCE {
   24   3:       OBJECT IDENTIFIER
         :         EdDSA 25519 signature algorithm { 1 3 101 112 }
         :       }
   29  25:     SEQUENCE {
   31  23:       SET {
   33  21:         SEQUENCE {
   35   3:           OBJECT IDENTIFIER commonName (2 5 4 3)
   40  14:           UTF8String 'IETF Test Demo'
         :           }
         :         }
         :       }
   56  30:     SEQUENCE {
   58  13:       UTCTime 01/08/2016 12:19:24 GMT
   73  13:       UTCTime 31/12/2040 23:59:59 GMT
         :       }
   88  25:     SEQUENCE {
   90  23:       SET {
   92  21:         SEQUENCE {
   94   3:           OBJECT IDENTIFIER commonName (2 5 4 3)
   99  14:           UTF8String 'IETF Test Demo'
         :           }
         :         }
         :       }
  115  42:     SEQUENCE {



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  117   5:       SEQUENCE {
  119   3:         OBJECT IDENTIFIER
         :           ECDH 25519 key agreement { 1 3 101 110 }
         :         }
  124  33:       BIT STRING
         :         85 20 F0 09 89 30 A7 54 74 8B 7D DC B4 3E F7 5A
         :         0D BF 3A 0D 26 38 1A F4 EB A4 A9 8E AA 9B 4E 6A
         :       }
  159  69:     [3] {
  161  67:       SEQUENCE {
  163  15:         SEQUENCE {
  165   3:           OBJECT IDENTIFIER basicConstraints (2 5 29 19)
  170   1:           BOOLEAN TRUE
  173   5:           OCTET STRING, encapsulates {
  175   3:             SEQUENCE {
  177   1:               BOOLEAN FALSE
         :               }
         :             }
         :           }
  180  14:         SEQUENCE {
  182   3:           OBJECT IDENTIFIER keyUsage (2 5 29 15)
  187   1:           BOOLEAN FALSE
  190   4:           OCTET STRING, encapsulates {
  192   2:             BIT STRING 3 unused bits
         :               '10000'B (bit 4)
         :             }
         :           }
  196  32:         SEQUENCE {
  198   3:           OBJECT IDENTIFIER subjectKeyIdentifier (2 5 29 14)
  203   1:           BOOLEAN FALSE
  206  22:           OCTET STRING, encapsulates {
  208  20:             OCTET STRING
         :               9B 1F 5E ED ED 04 33 85 E4 F7 BC 62 3C 59 75 B9
         :               0B C8 BB 3B
         :             }
         :           }
         :         }
         :       }
         :     }
  230   5:   SEQUENCE {
  232   3:     OBJECT IDENTIFIER
         :       EdDSA 25519 signature algorithm { 1 3 101 112 }
         :     }
  237  65:   BIT STRING
         :     AF 23 01 FE DD C9 E6 FF C1 CC A7 3D 74 D6 48 A4
         :     39 80 82 CD DB 69 B1 4E 4D 06 EC F8 1A 25 CE 50
         :     D4 C2 C3 EB 74 6C 4E DD 83 46 85 6E C8 6F 3D CE
         :     1A 18 65 C5 7A C2 7B 50 A0 C3 50 07 F5 E7 D9 07



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         :   }

  -----BEGIN CERTIFICATE-----
  MIIBLDCB36ADAgECAghWAUdKKo3DMDAFBgMrZXAwGTEXMBUGA1UEAwwOSUVURiBUZX
  N0IERlbW8wHhcNMTYwODAxMTIxOTI0WhcNNDAxMjMxMjM1OTU5WjAZMRcwFQYDVQQD
  DA5JRVRGIFRlc3QgRGVtbzAqMAUGAytlbgMhAIUg8AmJMKdUdIt93LQ+91oNvzoNJj
  ga9OukqY6qm05qo0UwQzAPBgNVHRMBAf8EBTADAQEAMA4GA1UdDwEBAAQEAwIDCDAg
  BgNVHQ4BAQAEFgQUmx9e7e0EM4Xk97xiPFl1uQvIuzswBQYDK2VwA0EAryMB/t3J5v
  /BzKc9dNZIpDmAgs3babFOTQbs+BolzlDUwsPrdGxO3YNGhW7Ibz3OGhhlxXrCe1Cg
  w1AH9efZBw==
  -----END CERTIFICATE-----

10.3.  Example Ed25519 Private Key

   An example of an Ed25519 private key:

   -----BEGIN PRIVATE KEY-----
   MC4CAQAwBQYDK2VwBCIEINTuctv5E1hK1bbY8fdp+K06/nwoy/HU++CXqI9EdVhC
   -----END PRIVATE KEY-----

11.  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, James Manger, Nikos Mavrogiannopoulos, Russ Housley, David
   Benjamin, and Alex Wilson.

   A big thank you to Symantec for kindly donating the OIDs used in this
   draft.

12.  IANA Considerations

   None.

13.  Security Considerations

   The security considerations of [RFC5280], [RFC7748], and
   [I-D.irtf-cfrg-eddsa] apply accordingly.

   The procedures for going from a private key to a public key is
   different for when used with Diffie-Helman and when used with Edwards
   Signatures.  This means that the same public key cannot be used for
   both ECDH and EdDSA.





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   In the original design of Ed25519 signatures, there was a known
   attack between the pure and the pre-hash version of the signatures.
   This has sense been corrected in the final version of the design.
   The initial problem meant that there was a known attack, and
   therefore a known reason to forbid the use of Ed25519 keys with the
   Ed25519ph signature scheme and visa versa.  With the change in the
   design this attack has been prevented.  This does not mean that the
   same Ed25519 key should be used with both schemes, there still may be
   attacks where collisions can be found.  For this reason, the same
   keys are not to be used for the pure and pre-hash versions of the
   scheme.  This applies to both curve 25519 and curve 448.

14.  References

14.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [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, DOI 10.17487/RFC5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC5480]  Turner, S., Brown, D., Yiu, K., Housley, R., and T. Polk,
              "Elliptic Curve Cryptography Subject Public Key
              Information", RFC 5480, DOI 10.17487/RFC5480, March 2009,
              <http://www.rfc-editor.org/info/rfc5480>.

   [RFC7748]  Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
              for Security", RFC 7748, DOI 10.17487/RFC7748, January
              2016, <http://www.rfc-editor.org/info/rfc7748>.

   [I-D.irtf-cfrg-eddsa]
              Josefsson, S. and I. Liusvaara, "Edwards-curve Digital
              Signature Algorithm (EdDSA)", draft-irtf-cfrg-eddsa-08
              (work in progress), August 2016.

   [RFC5958]  Turner, S., "Asymmetric Key Packages", RFC 5958,
              DOI 10.17487/RFC5958, August 2010,
              <http://www.rfc-editor.org/info/rfc5958>.







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14.2.  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, DOI 10.17487/RFC3279, April
              2002, <http://www.rfc-editor.org/info/rfc3279>.

   [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,
              DOI 10.17487/RFC4055, June 2005,
              <http://www.rfc-editor.org/info/rfc4055>.

   [RFC5639]  Lochter, M. and J. Merkle, "Elliptic Curve Cryptography
              (ECC) Brainpool Standard Curves and Curve Generation",
              RFC 5639, DOI 10.17487/RFC5639, March 2010,
              <http://www.rfc-editor.org/info/rfc5639>.

   [RFC5755]  Farrell, S., Housley, R., and S. Turner, "An Internet
              Attribute Certificate Profile for Authorization",
              RFC 5755, DOI 10.17487/RFC5755, January 2010,
              <http://www.rfc-editor.org/info/rfc5755>.

   [RFC7468]  Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
              PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
              April 2015, <http://www.rfc-editor.org/info/rfc7468>.

Authors' Addresses

   Simon Josefsson
   SJD AB

   Email: simon@josefsson.org


   Jim Schaad
   August Cellars

   Email: ietf@augustcellars.com










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