Internet DRAFT - draft-pala-composite-crypto
draft-pala-composite-crypto
Network Working Group M. Pala
Internet-Draft CableLabs
Intended status: Standards Track March 25, 2019
Expires: September 26, 2019
Composite Public Keys and Signatures
draft-pala-composite-crypto-03
Abstract
PKIs are used to provide scalability and ease key management. One
type of PKIs that is predominant for securing communications and data
is based on the X.509 standard. Since the security of PKIs,
ultimately, depends on the security of the cryptographic building
blocks that are used for authentication and encryption, the standards
community made algorithm agility a priority. Algorithm agility, in
particular, enables upgrading to newly available algorithms when
needed.
The CompositeCrypto (i.e., CompositeKey and CompositeSignature
structures) described in this document provides an additional tool
that enables the use of multiple algorithms to authenticate data
without the need to use multiple certificates and more complex data
structures.
This document provide the description of the definition and encoding
rules for CompositeKey and CompositeSignature. A description of how
to use these structures in main PKIX objects (e.g., X.509
certificates, CRLs, OCSP responses, etc.) is also 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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 26, 2019.
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Copyright Notice
Copyright (c) 2019 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
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described in the Simplified BSD License.
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 2
2. Introduction and Scope . . . . . . . . . . . . . . . . . . . 3
3. Composite Cryptography . . . . . . . . . . . . . . . . . . . 3
3.1. Composite Public Keys . . . . . . . . . . . . . . . . . . 4
3.2. Composite Private Keys . . . . . . . . . . . . . . . . . 4
3.2.1. Encoding Rules . . . . . . . . . . . . . . . . . . . 4
3.2.2. Encrypted and Un-encrypted Local Storage . . . . . . 4
3.2.3. Asymmetric Key Packages . . . . . . . . . . . . . . . 5
3.3. Composite Signatures . . . . . . . . . . . . . . . . . . 5
3.4. Generating Composite Signatures . . . . . . . . . . . . . 6
3.5. Verifying Composite Signatures . . . . . . . . . . . . . 6
4. Use of Composite Crypto in PKIX structures . . . . . . . . . 6
4.1. Use in X.509 Certificates . . . . . . . . . . . . . . . . 6
4.2. Use in X.509 CRLs . . . . . . . . . . . . . . . . . . . . 6
4.3. Use in X.509 OCSP Messages . . . . . . . . . . . . . . . 6
4.4. Use in PKCS#7 . . . . . . . . . . . . . . . . . . . . . . 6
4.5. Use in PKCS#8 . . . . . . . . . . . . . . . . . . . . . . 6
4.6. Use in PKCS#12 . . . . . . . . . . . . . . . . . . . . . 7
4.7. Use in CMS . . . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
8. Normative References . . . . . . . . . . . . . . . . . . . . 7
Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Requirements notation
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].
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2. Introduction and Scope
With the definition of new algorithms (e.g. more efficient factoring
techniques) and technologies (e.g., quantum-based computing devices)
that might be available in the near future, the need to provide an
easy-to-deploy and efficient solution capable of providing multi-
algorithms authentication is paramount.
Today there are no complete or general solutions that allow the use
of multiple public-key algorithms to authenticate PKIX data without
using multiple X.509 certificates or complex data structures. For
example, CRLs or OCSP responses can not be protected via multiple
algorithms without wrapping the OCSP responses' data via CMS or other
signed containers.
We define two new building blocks, i.e. compositeKey and
compositeSignature, that can be used in many environments where
Public Key authentication is used - i.e., from the generation of
certificates that are authenticated with multiple signatures (i.e.,
using multiple keys that may or may not use different cryptographic
schemes or different number of security bits), to the possibility of
specifying a composite key that combines multiple public keys
together (instead of one) in a single certificate.
This document describes the encoding of the new building blocks and
their application to different X.509 core data structures that are
used in PKIs. In particular, this document focuses only on the
definition of the composite keys and composite signatures definitions
for X.509 based PKIs (PKIX) by providing the encoding rules and their
usage in existing X.509 (PKIX) data structures.
3. Composite Cryptography
Composite Cryptography is defined as the possibility to combine
different public keys and signatures in PKIX objects. The following
OID is defined to identfy the algorithm class:
id-pk-compositeCrypto OBJECT IDENTIFIER ::= { iso(1)
identified-organization(3) dod(6) internet(1) private(4)
enterprise(1) OpenCA(18227) Algorithms(2) 1 }
Composite Cryptography provides three distinct building blocks: the
compositePublicKey, the compositePrivateKey and the
compositeSignature. The compositePublicKey is meant to carry all the
public keys associated with an identity. The compositePrivateKey is
meant to carry all the private keys associated with an identity. The
compositeSignature, instead, carries a sequence of signatures that
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are generated by using the different individual keys from a
compositePrivateKey.
3.1. Composite Public Keys
This document defines a new Object Identifier and data strcuture for
composite public keys as follows:
id-pk-compositePublicKey OBJECT IDENTIFIER ::= { id-kp-compositeCrypto 1 }
CompositePublicKey ::= SEQUENCE (1..MAX) OF SubjectPublicKeyInfo
3.2. Composite Private Keys
This section specifies a syntax and semantics for Composite Keys
private key information. Composite private key information is built
as a SEQUENCE of BIT STRINGs each of which contains the single
private keys and parameters. Additionally, it may include the
corresponding public keys.
The structure defined in this document allows for the distribution of
the composite keys (public and private) and the associated domain
parameters by using a sequence of OneAsymmetricKey as defined in
[RFC5958].
The Algorithm Identifier and data structure associated for Composite
Private Keys is defined as follows:
id-pk-compositePrivateKey OBJECT IDENTIFIER ::= { id-kp-compositeCrypto 2 }
CompositePrivateKey ::= SEQUENCE (1..MAX) OF OneAsymmetricKey
3.2.1. Encoding Rules
When encoding Composite Private Keys, generators SHOULD use
Distinguished Encoding Rules (DER) [X.690] and receivers SHOULD be
prepared to handle Basic Encoding Rules (BER) [X.690] and DER
[X.690].
3.2.2. Encrypted and Un-encrypted Local Storage
The compositePrivateKeys format as defined in the previous subsection
can also be used for local storage of an unencrypted
compositePrivateKeys binary object. The compositePrivateKeys can
also be formatted in PEM format that uses the (".pem") file extension
and which is encoded as the the Base64 encoding (see Section 4 of
[RFC4648]), of the DER-encoded compositePrivateKeys object with the
following armour:
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-----BEGIN COMPOSITE PRIVATE KEY-----
-----END COMPOSITE PRIVATE KEY-----
Local storage of an encrypted CompositePrivateKeys object is out of
scope of this document. However, CompositePrivateKeys should be the
format for the plaintext key being encrypted. DER [X.690] encoding
the CompositePrivateKeys will promote interoperability if the key is
encrypted for transport to another party. PEM encoding the DER-
encoded CompositePrivateKeys is common; "Proc-Type:" and "DEK-INFO:"
fields [RFC1421] followed by the DER-encoded CompositePrivateKeys.
The following armour used in this case is as follows:
-----BEGIN COMPOSITE PRIVATE KEY-----
-----END COMPOSITE PRIVATE KEY-----
3.2.3. Asymmetric Key Packages
The Cryptographic Message Syntax (CMS), as defined in RFC 5652, can
be used to digitally sign, digest, authenticate, or encrypt the
asymmetric key format content type.
When encoding Composite Private Keys, the privateKeyAlgorithm in the
OneAsymmetricKey SHALL be set to id-kp-compositePrivateKey.
The parameters of the privateKeyAlgorithm SHALL be a sequence of
AlgorithmIdentifier objects, each of which are encoded according to
the rules defined for each of the different keys in the Composite
Private Key.
The value of the privateKey field in the OneAsymmetricKey SHALL be
set to the DER encoding of the SEQUENCE of private key values that
make up the composite key. The number and order of elements in the
sequence SHALL be the same as identified in the sequence of
parameters in the privateKeyAlgorithm.
The value of the the publicKey (if present) SHALL be set to the DER
encoding of the SEQUENCE of publicKey values. If this field is
present, the number and order of elements SHALL be the same as
identified in the sequence of parameters in the privateKeyAlgorithm.
The value of the attributes is encoded as usual.
3.3. Composite Signatures
The use of composite signatures allows for the use of multiple
algorithms for authentication.
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id-pk-compositeSignature OBJECT IDENTIFIER ::= { compositeCrypto 3 }
CompositeSignature OBJECT IDENTIFIER ::= SEQUENCE (1..MAX) OF BITSTRING
3.4. Generating Composite Signatures
When generating a CompositeSignature, the signing entity MUST
generate one signature per key that is in the corresponding
compositePrivateKey set.
The value of the compositeSignature is the DER encoding of the
SEQUENCE of BIT STRING where each BIT STRING is the DER
representation of the signature generated with one of the private key
in the compositePrivateKey set.
When signing, the order of the signature MUST respect the order of
keys in the compositePrivateKey and compositePublicKey sets.
3.5. Verifying Composite Signatures
When validating a compositeSignature, the relying party MUST verify
at least one of the signatures in the compositeSignature structure
and SHOULD verify all of them.
The process of validating composite signatures starts with going
through the sequence of the signatures and if the inner signature
algorithm is supported, the relying party MUST verify the signature
with the corresponding public key in the compositePrivateKey.
The order of the signatures MUST respect the order of keys in the
compositePrivateKey and compositePublicKey sets.
4. Use of Composite Crypto in PKIX structures
4.1. Use in X.509 Certificates
4.2. Use in X.509 CRLs
4.3. Use in X.509 OCSP Messages
4.4. Use in PKCS#7
4.5. Use in PKCS#8
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4.6. Use in PKCS#12
4.7. Use in CMS
5. Security Considerations
This structures described in this document do not protect the private
keys information in any way unless combined with a security protocol
or encryption properties of the objects (if any) where the
CompositePrivateKey is used (see next Section).
Protection of the private key information is vital to public key
cryptography. The consequences of disclosure depend on the purpose
of the private key. If a private key is used for signature, then the
disclosure allows unauthorized signing. If a private key is used for
key management, then disclosure allows unauthorized parties to access
the managed keying material. The encryption algorithm used in the
encryption process must be as 'strong' as the key it is protecting.
6. IANA considerations
The CMS content type OID is registered in a DoD arc. The ASN.1
module OID is TBD. The id-pk-compositeCrypto, id-pk-
compositePrivateKey, id-pk-compositePublicKey, and id-pk-
compositeSignature OIDs are to be assigned by IANA. The authors
suggest to use the id-pkix arc for this usage.
7. Acknowledgments
The authors would like to thank everybody who provided insightful
comments and helped in any form. This document uses a lot of text
from similar documents ([RFC3279] and [RFC8410]) as well as [I-
D.ietf-lamps-cms-hash-sig]. Thanks go to the authors of those
documents. "Copying always makes things easier and less error prone"
- [RFC8411].
8. 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,
<https://www.rfc-editor.org/info/rfc2119>.
Appendix A. ASN.1 Module
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CompositeCrypto-2009 { iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) TBD }
DEFINITIONS IMPLICIT TAGS ::= BEGIN
EXPORTS ALL;
IMPORTS
PUBLIC-KEY, SIGNATURE-ALGORITHM
FROM AlgorithmInformation-2009 -- RFC 5911 [CMSASN1]
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-algorithmInformation-02(58) }
--
-- Object Identifiers
--
id-pk-compositeCrypto OBJECT IDENTIFIER ::= { iso(1)
identified-organization(3) dod(6) internet(1) private(4)
enterprise(1) OpenCA(18227) Algorithms(2) 1 }
id-pk-compositePublicKey OBJECT IDENTIFIER ::= {
id-kp-compositeCrypto 1 }
id-pk-compositePrivateKey OBJECT IDENTIFIER ::= {
id-kp-compositeCrypto 2 }
id-pk-compositeSignature OBJECT IDENTIFIER ::= {
id-kp-compositeCrypto 3 }
END
Author's Address
Massimiliano Pala
CableLabs
858 Coal Creek Cir
Louisville, CO 80027
USA
Email: director@openca.org
URI: http://www.linkedin.com/in/mpala
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