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IETF RFC 7935
Last modified on Thursday, September 1st, 2016
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Internet Engineering Task Force (IETF) G. Huston
Request for Comments: 7935 G. Michaelson, Ed.
Obsoletes: 6485 APNIC
Category: Standards Track August 2016
ISSN: 2070-1721
The Profile for Algorithms and Key Sizes
for Use in the Resource Public Key Infrastructure
 Abstract
This document specifies the algorithms, algorithms' parameters,
asymmetric key formats, asymmetric key size, and signature format for
the Resource Public Key Infrastructure (RPKI) subscribers that
generate digital signatures on certificates, Certificate Revocation
Lists (CRLs), Cryptographic Message Syntax (CMS) signed objects and
certification requests as well as for the relying parties (RPs) that
verify these digital signatures.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 7935.
Huston & Michaelson Standards Track PAGE 1 
RFC 7935 RPKI Algorithm Profile August 2016
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
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Asymmetric Key Pair Formats . . . . . . . . . . . . . . . . . 4
3.1. Public Key Format . . . . . . . . . . . . . . . . . . . . 5
3.2. Private Key Format . . . . . . . . . . . . . . . . . . . 5
4. Signature Format . . . . . . . . . . . . . . . . . . . . . . 5
5. Additional Requirements . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Changes Applied to RFC 6485 . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
Huston & Michaelson Standards Track PAGE 2
RFC 7935 RPKI Algorithm Profile August 2016
1. Introduction
This document specifies:
* the digital signature algorithm and parameters;
* the hash algorithm and parameters;
* the public and private key formats; and,
* the signature format
used by Resource Public Key Infrastructure (RPKI) [RFC 6480]
subscribers when they apply digital signatures to certificates and
Certificate Revocation Lists (CRLs) [RFC 5280], Cryptographic Message
Syntax (CMS) signed objects [RFC 5652] (e.g., Route Origin
Authorizations (ROAs) [RFC 6482] and manifests [RFC 6486]), and
certification requests [RFC 2986] [RFC 4211]. Relying parties (RPs)
also use the algorithms defined in this document to verify RPKI
subscribers' digital signatures [RFC 6480].
The RPKI profiles and specification documents that reference RFC 6485
now refer to this document; these documents include the RPKI
Certificate Policy (CP) [RFC 6484], the RPKI Certificate Profile
[RFC 6487], the RPKI Architecture [RFC 6480], and the Signed Object
Template for the RPKI [RFC 6488]. Familiarity with these documents is
assumed.
1.1. 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 [RFC 2119].
2. Algorithms
Two cryptographic algorithms are used in the RPKI:
* The signature algorithm used in certificates, CRLs, CMS signed
objects, and certification requests is RSA Public-Key
Cryptography Standards (PKCS) #1 Version 1.5 (sometimes
referred to as "RSASSA-PKCS1-v1_5") from Section 8.2 of
[RFC 3447].
Huston & Michaelson Standards Track PAGE 3
RFC 7935 RPKI Algorithm Profile August 2016
* The hashing algorithm used in certificates, CRLs, CMS signed
objects and certification requests is SHA-256 [SHS] (see note
below).
NOTE: The exception is the use of SHA-1 [SHS] when CAs generate
authority and subject key identifiers [RFC 6487].
In certificates, CRLs, and certification requests the hashing and
digital signature algorithms are identified together, i.e., "RSA
PKCS #1 v1.5 with SHA-256" or more simply "RSA with SHA-256". The
Object Identifier (OID) sha256WithRSAEncryption from [RFC 4055] MUST
be used in these products.
The OID is in the following locations:
In the certificate, the OID appears in the signature and
signatureAlgorithm fields [RFC 4055].
In the CRL, the OID appears in the signatureAlgorithm field
[RFC 4055].
In a certification request, the OID appears in the PKCS #10
signatureAlgorithm field [RFC 2986], or in the Certificate Request
Message Format (CRMF) POPOSigningKey algorithmIdentifier field
[RFC 4211].
In CMS SignedData, the hashing (message digest) and digital signature
algorithms are identified separately. The object identifier and
parameters for SHA-256 (as defined in [RFC 5754]) MUST be used for the
SignedData digestAlgorithms field and the SignerInfo digestAlgorithm
field. The object identifier and parameters for rsaEncryption
[RFC 3370] MUST be used for the SignerInfo signatureAlgorithm field
when generating CMS SignedData objects. RPKI implementations MUST
accept either rsaEncryption or sha256WithRSAEncryption for the
SignerInfo signatureAlgorithm field when verifying CMS SignedData
objects (for compatibility with objects produced by implementations
conforming to [RFC 6485]).
3. Asymmetric Key Pair Formats
The RSA key pairs used to compute the signatures MUST have a 2048-bit
modulus and a public exponent (e) of 65,537.
Huston & Michaelson Standards Track PAGE 4
RFC 7935 RPKI Algorithm Profile August 2016
3.1. Public Key Format
The subject's public key is included in subjectPublicKeyInfo
[RFC 5280]. It has two sub-fields: algorithm and subjectPublicKey.
The values for the structures and their sub-structures follow:
algorithm (which is an AlgorithmIdentifier type):
The object identifier for RSA PKCS #1 v1.5 with SHA-256 MUST be
used in the algorithm field, as specified in Section 5 of
[RFC 4055]. The value for the associated parameters from that
clause MUST also be used for the parameters field.
subjectPublicKey:
RSAPublicKey MUST be used to encode the certificate's
subjectPublicKey field, as specified in [RFC 4055].
3.2. Private Key Format
Local policy determines the private key format.
4. Signature Format
The structure for the certificate's signature field is as specified
in Section 1.2 of [RFC 4055]. The structure for the signature field
in the CMS SignedData's SignerInfos is as specified in [RFC 5652].
5. Additional Requirements
It is anticipated that the RPKI will require the adoption of updated
key sizes and a different set of signature and hash algorithms over
time, in order to maintain an acceptable level of cryptographic
security to protect the integrity of signed products in the RPKI.
This profile should be replaced to specify such future requirements,
as and when appropriate.
The procedures to implement such a transition of key sizes and
algorithms are specified in [RFC 6916].
6. Security Considerations
The Security Considerations of [RFC 4055], [RFC 5280], and [RFC 6487]
apply to certificates and CRLs. The Security Considerations of
[RFC 2986], [RFC 4211], and [RFC 6487] apply to certification requests.
The Security Considerations of [RFC 5754] apply to CMS signed objects.
No new security threats are introduced as a result of this
specification.
Huston & Michaelson Standards Track PAGE 5
RFC 7935 RPKI Algorithm Profile August 2016
7. Changes Applied to RFC 6485
This update includes a slight technical change to [RFC 6485] that is
considered to be outside the limited scope of an erratum. The
document update process has included other errata and also corrected
a number of nits.
Section 2 of [RFC 6485] specified sha256WithRSAEncryption as the OID
to use for the SignerInfo signatureAlgorithm field in CMS
SignedObjects. However, existing implementations use the
rsaEncryption OID for this field. (Support for rsaEncryption in
third-party cryptographic libraries is better than
sha256WithRSAEncryption, perhaps because [RFC 3370] says that support
for rsaEncryption is required, while support for OIDs that specify
both RSA and a digest algorithm is optional.)
Rather than force existing implementations to switch to
sha256WithRSAEncryption, this document was changed to follow existing
practice. This does not represent a cryptographic algorithm change,
just an identifier change. (Unlike certificates, CRLs, and
certification requests, CMS signed objects have a separate algorithm
identifier field for the hash (digest) algorithm, and that field is
already required to contain the id-sha256 OID per Section 2.)
To avoid compatibility problems, RPs are still required to accept
sha256WithRSAEncryption if encountered.
Other changes include:
* Minor wording and typo fixes.
* Corrections to references ([RFC 5652] instead of [RFC 3370],
[RFC 3447] instead of [RFC 4055]).
* Additional citations included in the Introduction.
* Correction to the CRMF POPOSigningKey field that is mentioned
in Section 2 (algorithmIdentifier instead of signature).
* Inclusion of certification requests in mentions of
certificates, CRLs, and CMS signed objects.
* Replacement of text in Section 5 with a pointer to the
procedures specified in [RFC 6916] (algorithm agility).
* Replacement of "signed object" with "CMS signed object"
everywhere.
Huston & Michaelson Standards Track PAGE 6
RFC 7935 RPKI Algorithm Profile August 2016
8. References
8.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<http://www.rfc-editor.org/info/RFC 2119>.
[RFC 2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification
Request Syntax Specification Version 1.7", RFC 2986,
DOI 10.17487/RFC 2986, November 2000,
<http://www.rfc-editor.org/info/RFC 2986>.
[RFC 3370] Housley, R., "Cryptographic Message Syntax (CMS)
Algorithms", RFC 3370, DOI 10.17487/RFC 3370, August 2002,
<http://www.rfc-editor.org/info/RFC 3370>.
[RFC 3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, DOI 10.17487/RFC 3447, February
2003, <http://www.rfc-editor.org/info/RFC 3447>.
[RFC 4055] 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/RFC 4055, June 2005,
<http://www.rfc-editor.org/info/RFC 4055>.
[RFC 4211] Schaad, J., "Internet X.509 Public Key Infrastructure
Certificate Request Message Format (CRMF)", RFC 4211,
DOI 10.17487/RFC 4211, September 2005,
<http://www.rfc-editor.org/info/RFC 4211>.
[RFC 5280] 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/RFC 5280, May 2008,
<http://www.rfc-editor.org/info/RFC 5280>.
[RFC 5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC 5652, September 2009,
<http://www.rfc-editor.org/info/RFC 5652>.
[RFC 5754] Turner, S., "Using SHA2 Algorithms with Cryptographic
Message Syntax", RFC 5754, DOI 10.17487/RFC 5754, January
2010, <http://www.rfc-editor.org/info/RFC 5754>.
Huston & Michaelson Standards Track PAGE 7
RFC 7935 RPKI Algorithm Profile August 2016
[RFC 6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, DOI 10.17487/RFC 6480,
February 2012, <http://www.rfc-editor.org/info/RFC 6480>.
[RFC 6484] Kent, S., Kong, D., Seo, K., and R. Watro, "Certificate
Policy (CP) for the Resource Public Key Infrastructure
(RPKI)", BCP 173, RFC 6484, DOI 10.17487/RFC 6484, February
2012, <http://www.rfc-editor.org/info/RFC 6484>.
[RFC 6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for
X.509 PKIX Resource Certificates", RFC 6487,
DOI 10.17487/RFC 6487, February 2012,
<http://www.rfc-editor.org/info/RFC 6487>.
[RFC 6488] Lepinski, M., Chi, A., and S. Kent, "Signed Object
Template for the Resource Public Key Infrastructure
(RPKI)", RFC 6488, DOI 10.17487/RFC 6488, February 2012,
<http://www.rfc-editor.org/info/RFC 6488>.
[SHS] National Institute of Standards and Technology (NIST),
"FIPS Publication 180-3: Secure Hash Standard", FIPS
Publication 180-3, October 2008.
8.2. Informative References
[RFC 6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
Origin Authorizations (ROAs)", RFC 6482,
DOI 10.17487/RFC 6482, February 2012,
<http://www.rfc-editor.org/info/RFC 6482>.
[RFC 6485] Huston, G., "The Profile for Algorithms and Key Sizes for
Use in the Resource Public Key Infrastructure (RPKI)",
RFC 6485, DOI 10.17487/RFC 6485, February 2012,
<http://www.rfc-editor.org/info/RFC 6485>.
[RFC 6486] Austein, R., Huston, G., Kent, S., and M. Lepinski,
"Manifests for the Resource Public Key Infrastructure
(RPKI)", RFC 6486, DOI 10.17487/RFC 6486, February 2012,
<http://www.rfc-editor.org/info/RFC 6486>.
[RFC 6916] Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility
Procedure for the Resource Public Key Infrastructure
(RPKI)", BCP 182, RFC 6916, DOI 10.17487/RFC 6916, April
2013, <http://www.rfc-editor.org/info/RFC 6916>.
Huston & Michaelson Standards Track PAGE 8
RFC 7935 RPKI Algorithm Profile August 2016
Acknowledgments
The authors acknowledge the reuse in this document of material
originally contained in working drafts of the RPKI Certificate Policy
[RFC 6484] and resource certificate profile [RFC 6487] documents. The
coauthors of these two documents -- namely, Stephen Kent, Derrick
Kong, Karen Seo, Ronald Watro, George Michaelson, and Robert Loomans
-- are acknowledged, with thanks. The constraint on key size noted
in this profile is the outcome of comments from Stephen Kent and
review comments from David Cooper. Sean Turner has provided
additional review input to this document.
Andrew Chi and David Mandelberg discovered the issue addressed in
this replacement of [RFC 6485], and the changes in this updated
specification reflect the outcome of a discussion between Rob Austein
and Matt Lepinski on the SIDR Working group mailing list. Richard
Hansen contributed a significant number of suggestions that have been
incorporated into this document.
Authors' Addresses
Geoff Huston
APNIC
Email: gih@apnic.net
George Michaelson (editor)
APNIC
Email: ggm@apnic.net
Huston & Michaelson Standards Track PAGE 9
RFC TOTAL SIZE: 17952 bytes
PUBLICATION DATE: Thursday, September 1st, 2016
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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