Network Working Group D. Brown
InternetDraft E. Chin
Intended status: Standards Track C. Tse
Expires: December 13, 2007 Certicom Corp.
June 11, 2007
ECC Algorithms for MIKEY
draftietfmsecmikeyecc03
Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2007).
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Abstract
This document proposes extensions to the authentication, encryption
and digital signature methods described for use in MIKEY, employing
ellipticcurve cryptography (ECC). These extensions are defined to
align MIKEY with other ECC implementations and standards.
It should be noted that this document is not selfcontained; it uses
the notations and definitions of [RFC3830].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. MIKEYDHSIGN with ECDSA or ECGDSA . . . . . . . . . . . . . . 5
3. MIKEYDHSIGN with ECDH . . . . . . . . . . . . . . . . . . . . 6
4. MIKEYECIES . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. MIKEYECMQV . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Additional Payload Encoding . . . . . . . . . . . . . . . . . 11
6.1. ECC Point payload (ECCPT) . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18
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1. Introduction
This document describes additional algorithms for use in MIKEY. The
document assumes that the reader is familiar with the MIKEY protocol.
The MIKEY protocol [RFC3830] defines three methods for transporting
or establishing keys: with the use of a preshared key, publickey
encryption (MIKEYRSA), and DiffieHellman (DH) key exchange (MIKEY
DHSIGN). This document extends MIKEYDHSIGN to use Elliptic Curve
Digital Signature Algorithm (ECDSA) or Elliptic Curve German Digital
Signature Algorithm (ECGDSA) as the signature algorithm and further
extends MIKEYDHSIGN to use Elliptic Curve DiffieHellman (ECDH)
groups. In addition, this document introduces two new methods based
on the the Elliptic Curve Integrated Encryption Scheme (ECIES) and
Elliptic Curve MenezesQuVanstone (ECMQV). The ECIES method (MIKEY
ECIES) is similar to MIKEYRSA method, and the ECMQV method (MIKEY
ECMQV) is similar to MIKEYDHSIGN method.
Implementations have shown that elliptic curve algorithms can
significantly improve performance and securityperbit over other
recommended algorithms. The purpose of this document is to expand
the options available to implementers of MIKEY to take advantage of
these benefits.
In addition, elliptic curve algorithms are capable of providing
security consistent with AES keys of 128, 192, and 256 bits without
extensive growth in asymmetric key sizes. The following table, taken
from [HOF] and [LEN], gives approximate comparable key sizes for
symmetric systems, ECC systems, and DH/DSA/RSA systems. The
estimates are based on the running times of the best algorithms known
today.
Symmetric  ECC2N  ECP  DH/DSA/RSA
80  163  192  1024
128  283  256  3072
192  409  384  7680
256  571  521  15360
Table 1: Comparable key sizes
Thus, for example, when securing a 192bit symmetric key, it is
prudent to use either 409bit ECC2N, 384bit ECP, or 7680bit DH/DSA/
RSA. With smaller key sizes the symmetric keys would be
underprotected.
Section 2 describes the extension of MIKEYDHSIGN to use the ECDSA or
ECGDSA signature algorithm. Section 3 describes the extension of
MIKEYDHSIGN to use ECDH groups. Section 4 describes the MIKEYECIES
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method. Section 5 describes the MIKEYECMQV method. Section 6
describes additional payloads required to support these new methods.
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. MIKEYDHSIGN with ECDSA or ECGDSA
MIKEYDHSIGN is described in Section 3.3 of [RFC3830]. The
Initiator's message includes SIGNi, a signature covering the
Initiator's message. As well, the Responder's message includes
SIGNr, a signature covering the Responder's message. According to
Section 4.2.6 of [RFC3830], the signature algorithm applied is
defined by, and dependent on the certificate used. It is MANDATORY
to support RSA PKCS#1, v1.5, and it is RECOMMENDED to support RSA
PSS. Instead of these signature algorithms, ECDSA or ECGDSA may be
used to allow shorter and more efficient signatures.
ECDSA signatures are detailed in [ANSIX9.62] and ECGDSA signatures
are detailed in [ISOIEC159462]. Curve selection and other
parameters will be defined by, and dependent on the certificate used.
When generating signatures, the hash function that MUST be used
depends on the key size, as follows:
ECC2N  ECP  Hash To Use
163  192  SHA1
233  224  SHA224
283  256  SHA256
409  384  SHA384
571  521  SHA512
Table 2: Hash to use with ECDSA and ECGDSA
The signature payload (SIGN) specified in Section 6.5 of [RFC3830]
can be used without modification. Two additional S types for ECDSA
and ECGDSA are defined as follows:
S type  Value  Comments

ECDSA  2  ECDSA signature [ANSI_X9.62]
ECGDSA  3  ECGDSA signature [ISO/IEC_159462]
[RFC3279] describes algorithms and identifiers for Internet X.509
certificates and CRLs. It includes ECC algorithms and identifiers.
To use the ECDSA or ECGDSA signature algorithm with Elliptic Curve
DiffieHellman, this extension to MIKEYDHSIGN may be combined with
the extension described in Section 3.
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3. MIKEYDHSIGN with ECDH
MIKEYDHSIGN is described in Section 3.3 of [RFC3830]. According to
Section 4.2.7 of [RFC3830], the support for OAKLEY 5 is MANDATORY and
support for OAKLEY 1 and OAKLEY 2 are OPTIONAL. Instead of these
DiffieHellman (DH) groups, elliptic curve DiffieHellman (ECDH)
groups may significantly improve performance and security.
The ECDH groups to be used by MIKEY are the groups recommended by
NIST in FIPS 1862 [FIPS1862]. Detailed descriptions of the ECDH
groups can be found in each of FIPS 1862 [FIPS1862] and SEC 2
[SEC2]. The ECDH groups use elliptic curves over GF[2^N] with N
prime or over GF[P] with P prime. Eleven of the groups proposed here
have been assigned identifiers by IANA [IANA] and the remaining five
might later be assigned identifiers by IANA. The group with IANA
number 6 is described in [ANSIX9.62] and [SEC2], with object
identifier sect163r1, but it is not one of the fifteen curves that
NIST recommends [FIPS1862]. The remaining NIST recommended groups
are suggested and anticipated to be assigned IANA numbers as
specified in Table 3.
id Group Type Group Description NIST Name SEC 2 OID
    
22 2 ECP ECPRGF192Random P192 secp192r1
23 3 EC2N EC2NGF163Random B163 sect163r2
7 3 EC2N EC2NGF163Koblitz K163 sect163k1
6 3 EC2N EC2NGF163Random2 none sect163r1
24 2 ECP ECPRGF224Random P224 secp224r1
25 3 EC2N EC2NGF233Random B233 sect233r1
26 3 EC2N EC2NGF233Koblitz K233 sect233k1
19 2 ECP ECPRGF256Random P256 secp256r1
8 3 EC2N EC2NGF283Random B283 sect283r1
9 3 EC2N EC2NGF283Koblitz K283 sect283k1
20 2 ECP ECPRGF384Random P384 secp384r1
10 3 EC2N EC2NGF409Random B409 sect409r1
11 3 EC2N EC2NGF409Koblitz K409 sect409k1
21 2 ECP ECPRGF521Random P521 secp521r1
12 3 EC2N EC2NGF571Random B571 sect571r1
13 3 EC2N EC2NGF571Koblitz K571 sect571k1
Table 3: Recommended Groups and Names
The ECDH groups in Table 3 are arranged into 5 classes, corresponding
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to approximately equivalent security strengths. To encourage
interoperability, implementations that support one of these classes,
SHOULD support the one group in that class that is defined over a
prime field (which will be one of P192, P224, P256, P384, or
P521). Implementations SHOULD support one of P256 or P384.
Implementations MAY support any set of groups.
The DH data payload (DH) specified in Section 6.4 of [RFC3830] can be
used without modification. Additional DHGroup identifiers are
required as follows:
DHGroup  Value

ECPRGF192Random / P192 / secp192r1  3
EC2NGF163Random / B163 / sect163r2  4
EC2NGF163Koblitz / K163 / sect163k1  5
EC2NGF163Random2 / none / sect163r1  6

ECPRGF224Random / P224 / secp224r1  7
EC2NGF233Random / B233 / sect233r1  8
EC2NGF233Koblitz / K233 / sect233k1  9

ECPRGF256Random / P256 / secp256r1  10
EC2NGF283Random / B283 / sect283r1  11
EC2NGF283Koblitz / K283 / sect283k1  12

ECPRGF384Random / P384 / secp384r1  13
EC2NGF409Random / B409 / sect409r1  14
EC2NGF409Koblitz / K409 / sect409k1  15

ECPRGF521Random / P521 / secp521r1  16
EC2NGF571Random / B571 / sect571r1  17
EC2NGF571Koblitz / K571 / sect571k1  18
When using the ECDH groups, the DHvalue in the DH data payload (DH)
is the octet string representation specified in ANSI X9.62
[ANSIX9.62] and [SEC1].
If the initiator chooses secret i and the responder chooses secret r,
then the raw shared secret is the xcoordinate(only) of (ir)*G.
To use ECDH and ECDSA signature algorithm or to use ECDH and ECGDSA
signature algorithm, this extension to MIKEYDHSIGN may be combined
with the extension described in Section 2.
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4. MIKEYECIES
The Elliptic Curve Integrated Encryption Scheme (ECIES) is a public
key encryption scheme based on ECC. Section 3.2 of [RFC3830] already
specifies a publickey encryption method (MIKEYRSA). Here we
describe the new MIKEYECIES method.
Initiator Responder
I_MESSAGE =
HDR, T, RAND, [IDiCERTi], [IDr], {SP},
KEMAC, [CHASH], PKE, SIGNi >
R_MESSAGE =
[<] HDR, T, [IDr], V
As with the MIKEYRSA case, the main objective of the Initiator's
message is to transport one or more TGKs and a set of security
parameters to the Responder in a secure manner. In general, the
MIKEYECIES and MIKEYRSA methods are exactly the same, except that
the supported signature algorithm and the public key encryption
algorithm are different.
The signature algorithm applied is defined by, and dependent on the
certificate used. The MIKEYECIES method supports ECDSA as described
in [ANSIX9.62] and ECGDSA as described in [ISOIEC159462]. The
SIGNi will use either ECDSA or ECGDSA as a signature algorithm, as
described in Section 2.
The public key encryption algorithm applied is defined by, and
dependent on the certificate used. The MIKEYECIES method supports
ECIES as described in detail in [SEC1]. For ECIES, the key
derivation function that MUST be used is ANSIX9.63KDF as described
in [SEC1]. As well, the MAC scheme that MUST be used is HMACSHA1
160. The 'standard' elliptic curve DiffieHellman primitive MUST be
used (as opposed to 'cofactor'). The symmetric encryption scheme
that MUST be used depends on the key size, as follows:
ECC2N  ECP  Symmetric Cipher To Use
163  192  3DESCBC
233  224  AES128CBC
283  256  AES128CBC
409  384  AES256CBC
571  521  AES256CBC
Table 4: Symmetric cipher to use with ECIES
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5. MIKEYECMQV
ECMQV (Elliptic Curve MenezesQuVanstone) is defined in ANSI X9.63
[ANSIX9.63]. ECMQV provides mutual authentication between the
communicating parties and key establishment for the secure transport
of data. Here we describe the new MIKEYECMQV method based on the
2pass protocol.
Initiator Responder
I_MESSAGE =
HDR, T, RAND, [IDiCERTi], [IDr],
{SP}, ECCPTi, SIGNi >
R_MESSAGE =
[<] HDR, T, [IDrCERTr],
IDi, ECCPTr, ECCPTi, V
The MIKEYECMQV method is similar to the MIKEYDHSIGN method, except
that with MIKEYECMQV, a variablelength shared secret is created
using ECMQV instead of a fixedlength shared secret. Same as the
MIKEYDHSIGN method, this method cannot be used to create group keys;
it can only be used to create single peertopeer keys.
The MIKEYECMQV method create a variablelength shared secret. From
this shared secret, the TGK and the auth_key for the Responder's
verification message are derived. The first portion of the shared
secret is the TGK, and the second portion of the shared secret is the
auth_key. The length of TGK is specified in ECCPT payload by the
Initiator. The length of auth_key is derived from the authentication
algorithm, which is also specified in ECCPT payload by the Initiator.
The main objective of the Initiator's message is to provide the
Responder with its ephemeral public key represented by the elliptic
curve point (ECCPTi), and a set of security protocol parameters.
These parameters include the authentication algorithm for the
Responder's verification message, the length of TGK, and the key
validity information.
The SIGNi is a signature covering the Initiator's message using the
Initiator's signature key from the Initiator's certificate. The
signature algorithm applied is defined by, and dependent on the
certificate used. The MIKEYECMQV method supports ECDSA as described
in [ANSIX9.62] and ECGDSA as described in [ISOIEC159462]. The
SIGNi will use either ECDSA or ECGDSA as a signature algorithm, as
described in Section 2.
The main objective of the Responder's message is to provide the
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Initiator with its ephemeral public key represented by the elliptic
curve point (ECCPTr). The set of security protocol parameters are
the same as the one in the Initiator's message.
If the Initiator's message is authenticated and accepted by the
Responder, and the ECMQV shared secret is created successfully, then
the verification message (V) is created using the auth_key. V is
calculated in the same way as in the MIKEYPSA method (see Section
5.2 of [RFC3830]).
If the Responder does not support the set of parameters suggested by
the Initiator, the error message SHOULD include the supported
parameters (see Section 5.1.1 of [ANSIX9.63]).
The error message is formed as:
HDR, T, {ERR}, {SP}, [SIGNr]
In case of error, the ECMQV shared secret should not be computed.
Without the shared secret, V cannot be generated. As a result, the
error message should include a SIGNr instead of V, in the cases when
the Responder is able to authenticate the Initiator's message.
The SIGNr is a signature covering the Responder's error message using
the Responder's signature key from the Responder's certificate. The
signature algorithm applied is defined by, and dependent on the
certificate used. The MIKEYECMQV method support ECDSA as described
in [ANSIX9.62] and ECGDSA as described in [ISOIEC159462]. The
SIGNi will use either ECDSA or ECGDSA as a signature algorithm, as
described in Section 2.
2pass ECMQV is described in detail in ANSI X9.63 [ANSIX9.63].
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6. Additional Payload Encoding
6.1. ECC Point payload (ECCPT)
The ECCPT payload carries a point on the elliptic curve used in
MIKEYECMQV. The payload identifier is 22.
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+++++++++++++++++++++++++++++++++
! Next payload ! ECC Curve ! ECC Point ~
+++++++++++++++++++++++++++++++++
! Auth alg ! TGK len ! Reserv! KV !
+++++++++++++++++++++++++++++++++
! KV data (optional) ~
+++++++++++++++++++++++++++++++++
* Next payload (8 bits): identifies the payload that is added after
this payload. See Section 6.1 of [RFC3830] for values.
* ECC curve (8 bits): identifies the ECC curve used.
ECC curve  Value

ECPRGF192Random / P192 / secp192r1  0
EC2NGF163Random / B163 / sect163r2  1
EC2NGF163Koblitz / K163 / sect163k1  2
EC2NGF163Random2 / none / sect163r1  3
ECPRGF224Random / P224 / secp224r1  4
EC2NGF233Random / B233 / sect233r1  5
EC2NGF233Koblitz / K233 / sect233k1  6
ECPRGF256Random / P256 / secp256r1  7
EC2NGF283Random / B283 / sect283r1  8
EC2NGF283Koblitz / K283 / sect283k1  9
ECPRGF384Random / P384 / secp384r1  10
EC2NGF409Random / B409 / sect409r1  11
EC2NGF409Koblitz / K409 / sect409k1  12
ECPRGF521Random / P521 / secp521r1  13
EC2NGF571Random / B571 / sect571r1  14
EC2NGF571Koblitz / K571 / sect571k1  15
* ECC point (variable length): ECC point data, padded to end on a
32bit boundary, encoded in octet string representation specified
in ANSI X9.62 [ANSIX9.62] and [SEC1]. Uncompressed format MUST be
supported. Hybrid and compressed formats MAY be supported.
* Auth alg (8 bits): specifies the MAC algorithm used for the
verification message. See Section 6.2 of [RFC3830] for defined
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values.
* TGK len (16 bits): the length of the TGK (in bytes).
* KV (4 bits): indicates the type of key validity period specified.
This may be done by using an SPI (alternatively an MKI in SRTP) or
by providing an interval in which the key is valid (e.g., in the
latter case, for SRTP this will be the index range where the key
is valid). See Section 6.13 of [RFC3830] for predefined values.
* KV data (variable length): This includes either the SPI/MKI or an
interval (see Section 6.14 of [RFC3830]). If KV is NULL, this
field is not included.
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7. Security Considerations
Since this document proposes new methods for use within MIKEY, many
of the security considerations contained within [RFC3830] apply here
as well. Some of the methods proposed in this document offer higher
cryptographic strength than those proposed in [RFC3830]. In
particular, there are elliptic curves corresponding to each of the
symmetric key sizes 80 bits, 128 bits, 192 bits, and 256 bits. This
allows the MIKEY key exchange to offer security comparable with
higherstrength AES algorithms and SHA implementations. The methods
proposed in this document are among those standardized by NIST in
FIPS 1862 [FIPS1862], by the SECG in SEC2 [SEC2], and by ANSI in
ANSI X9.62 [ANSIX9.62] and X9.63 [ANSIX9.63].
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8. IANA Considerations
This document adds entries to existing MIKEY namespaces in Section 2
(S types in signature payloads), Section 3 (DH Group identifier in DH
payloads), Section 6.1 (ECCPT payload identifier), and Section 6.1
(ECC curve).
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9. References
9.1. Normative References
[ANSIX9.62]
American National Standards Institute, "ANSI X9.62: Public
Key Cryptography For The Financial Services Industry: The
Elliptic Curve Digital Signature Algorithm (ECDSA)", 2005.
[ANSIX9.63]
American National Standards Institute, "ANSI X9.63: Public
Key Cryptography For The Financial Services Industry: Key
Agreement and Key Transport using Elliptic Curve
Cryptography", 2001.
[FIPS1862]
National Institute of Standards and Technology, "FIPS
1862 Digital Signature Standard", 2000.
[IANA] Internet Assigned Numbers Authority, "Attribute Assigned
Numbers.", .
[ISOIEC159462]
International Organization for Standardization and
International Electrotechnical Commission, "ISO/IEC
159462: Information technology  Security techniques 
Cryptographic techniques based on elliptic curves  Part
2: Digital signatures", 2002.
[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.
[RFC3830] Arkko, J., Carrara, E., Lindholm, F., Naslund, M., and K.
Norrman, "MIKEY: Multimedia Internet KEYing", RFC 3830,
August 2004.
[SEC1] Standards for Efficient Cryptography Group, "Elliptic
Curve Cryptography", September 2000.
[SEC2] Standards for Efficient Cryptography Group, "Recommended
Elliptic Curve Domain Parameters", September 2000.
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9.2. Informative References
[HOF] Hoffman, P. and H. Orman, "Determining strengths for
public keys used for exchanging symmetric keys",
August 2000.
[LEN] Lenstra, A. and E. Verhuel, "Selecting cryptographic key
sizes", .
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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Authors' Addresses
Daniel R. L. Brown
Certicom Corp.
5520 Explorer Drive
Mississauga, Ontario L4W 5L1
CANADA
Phone: +19055074220
Fax: +19055074230
Email: dbrown@certicom.com
URI: http://www.certicom.com
Eugene Chin
Certicom Corp.
5520 Explorer Drive
Mississauga, Ontario L4W 5L1
CANADA
Phone: +19055074220
Fax: +19055074230
Email: echin@certicom.com
URI: http://www.certicom.com
Chi Chiu Tse
Certicom Corp.
5520 Explorer Drive
Mississauga, Ontario L4W 5L1
CANADA
Phone: +19055074220
Fax: +19055074230
Email: ctse@certicom.com
URI: http://www.certicom.com
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