draft-ietf-smime-key-wrap-00.txt   draft-ietf-smime-key-wrap-01.txt 
S/MIME Working Group R. Housley S/MIME Working Group R. Housley
Internet Draft RSA Laboratories Internet Draft RSA Laboratories
expires in six months September 2001 expires in six months September 2001
Triple-DES and RC2 Key Wrapping Triple-DES and RC2 Key Wrapping
<draft-ietf-smime-key-wrap-00.txt> <draft-ietf-smime-key-wrap-01.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
skipping to change at page 2, line 19 skipping to change at page 2, line 19
wrap algorithms are commonly used in two situations. First, key wrap algorithms are commonly used in two situations. First, key
agreement algorithms (such as Diffie-Hellman [DH-X9.42]) generate a agreement algorithms (such as Diffie-Hellman [DH-X9.42]) generate a
pairwise key-encryption key, and a key wrap algorithm is used to pairwise key-encryption key, and a key wrap algorithm is used to
encrypt the content-encryption key or a multicast key with the encrypt the content-encryption key or a multicast key with the
pairwise key-encryption key. Second, a key wrap algorithm is used to pairwise key-encryption key. Second, a key wrap algorithm is used to
encrypt the content-encryption key, multicast key, or session key in encrypt the content-encryption key, multicast key, or session key in
a locally generated storage key-encryption key or a key-encryption a locally generated storage key-encryption key or a key-encryption
key that was distributed out-of-band. key that was distributed out-of-band.
This document specifies the algorithm for wrapping one Triple-DES key This document specifies the algorithm for wrapping one Triple-DES key
with another Triple-DES key [3DES] and specifies the algorithm for with another Triple-DES key [3DES], and it specifies the algorithm
wrapping one RC2 key with another RC2 key [RC2]. Encryption of a for wrapping one RC2 key with another RC2 key [RC2]. Encryption of a
Triple-DES key with another Triple-DES key uses the algorithm Triple-DES key with another Triple-DES key uses the algorithm
specified in section 3. Encryption of a RC2 key with another RC2 key specified in section 3. Encryption of a RC2 key with another RC2 key
uses the algorithm specified in section 4. Both of these algorithms uses the algorithm specified in section 4. Both of these algorithms
rely on the key checksum algorithm specified in section 2. Triple- rely on the key checksum algorithm specified in section 2. Triple-
DES and RC2 content-encryption keys are encrypted in Cipher Block DES and RC2 content-encryption keys are encrypted in Cipher Block
Chaining (CBC) mode [MODES]. Chaining (CBC) mode [MODES].
In this document, the key words MUST, MUST NOT, REQUIRED, SHOULD, In this document, the key words MUST, MUST NOT, REQUIRED, SHOULD,
SHOULD NOT, RECOMMENDED, and MAY are to be interpreted as described SHOULD NOT, RECOMMENDED, and MAY are to be interpreted as described
by Scott Bradner in [STDWORDS]. by Scott Bradner in [STDWORDS].
The same key wrap algorithm is used for both Two-key Triple-DES and
Three-key Triple-DES keys. When a Two-key Triple-DES key is to be
wrapped, a third DES key with the same value as the first DES key is
created. Thus, all wrapped Triple-DES keys include three DES keys.
However, a Two-key Triple-DES key MUST NOT be used to wrap a Three-
key Triple-DES key that is comprised of three unique DES keys.
RC2 supports variable length keys. RC2 128-bit keys MUST be used as
key-encryption keys; however, the wrapped RC2 key MAY be of any size.
2 Key Checksum 2 Key Checksum
The key checksum algorithm is used to provide a key integrity check The key checksum algorithm is used to provide a key integrity check
value. The algorithm is: value. The algorithm is:
1. Compute a 20 octet SHA-1 [SHA1] message digest on the key 1. Compute a 20 octet SHA-1 [SHA1] message digest on the key
that is to be wrapped. that is to be wrapped.
2. Use the most significant (first) eight octets of the message 2. Use the most significant (first) eight octets of the message
digest value as the checksum value. digest value as the checksum value.
3 Triple-DES Key Wrapping and Unwrapping 3 Triple-DES Key Wrapping and Unwrapping
This section specifies the algorithms for wrapping and unwrapping one This section specifies the algorithms for wrapping and unwrapping one
Triple-DES key with another Triple-DES key [3DES]. Triple-DES key with another Triple-DES key [3DES].
The same key wrap algorithm is used for both Two-key Triple-DES and
Three-key Triple-DES keys. When a Two-key Triple-DES key is to be
wrapped, a third DES key with the same value as the first DES key is
created. Thus, all wrapped Triple-DES keys include three DES keys.
However, a Two-key Triple-DES key MUST NOT be used to wrap a Three-
key Triple-DES key that is comprised of three unique DES keys.
3.1 Triple-DES Key Wrap 3.1 Triple-DES Key Wrap
The Triple-DES key wrap algorithm encrypts a Triple-DES key with a The Triple-DES key wrap algorithm encrypts a Triple-DES key with a
Triple-DES key-encryption key. The Triple-DES key wrap algorithm is: Triple-DES key-encryption key. The Triple-DES key wrap algorithm is:
1. Set odd parity for each of the DES key octets comprising the 1. Set odd parity for each of the DES key octets comprising the
Three-Key Triple-DES key that is to be wrapped, call the result Three-Key Triple-DES key that is to be wrapped, call the result
CEK. CEK.
2. Compute an 8 octet key checksum value on CEK as described above 2. Compute an 8 octet key checksum value on CEK as described above
in Section 2, call the result ICV. in Section 2, call the result ICV.
skipping to change at page 4, line 30 skipping to change at page 4, line 24
Some security protocols employ ASN.1 [X.208-88, X.209-88], and these Some security protocols employ ASN.1 [X.208-88, X.209-88], and these
protocols employ algorithm identifiers to name cryptographic protocols employ algorithm identifiers to name cryptographic
algorithms. To support these protocols, the Triple-DES key wrap algorithms. To support these protocols, the Triple-DES key wrap
algorithm has been assigned the following algorithm identifier: algorithm has been assigned the following algorithm identifier:
id-alg-CMS3DESwrap OBJECT IDENTIFIER ::= { iso(1) member-body(2) id-alg-CMS3DESwrap OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) alg(3) 6 } us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) alg(3) 6 }
The AlgorithmIdentifier parameter field MUST be NULL. The AlgorithmIdentifier parameter field MUST be NULL.
3.4 Triple-DES Key Wrap Example
This section contains a Triple-DES Key Wrap example. Intermediate
values corresponding to the named items in section 3.1 are given in
hexadecimal.
CEK: 2923 bf85 e06d d6ae 5291 49f1 f1ba e9ea b3a7 da3d 860d 3e98
KEK: 255e 0d1c 07b6 46df b313 4cc8 43ba 8aa7 1f02 5b7c 0838 251f
ICV: 181b 7e96 86e0 4a4e
CEKICV: 2923 bf85 e06d d6ae 5291 49f1 f1ba e9ea b3a7 da3d 860d 3e98
181b 7e96 86e0 4a4e
IV: 5dd4 cbfc 96f5 453b
TEMP1: cfc1 a789 c675 dd2a b49a 3204 ef92 cc03 5c1f 3b97 7a79 60f6
a44d cc5f 729d 8449
TEMP2: 5dd4 cbfc 96f5 453b cfc1 a789 c675 dd2a b49a 3204 ef92 cc03
5c1f 3b97 7a79 60f6 a44d cc5f 729d 8449
TEMP3: 4984 9d72 5fcc 4da4 f660 797a 3b97 1f5c 03cc 92ef 0432 9ab4
2add 75c6 89a7 c1cf 3b45 f596 fccb d45d
RESULT: 6901 0761 8ef0 92b3 b48c a179 6b23 4ae9 fa33 ebb4 1596 0403
7db5 d6a8 4eb3 aac2 768c 6327 75a4 67d4
4 RC2 Key Wrapping and Unwrapping 4 RC2 Key Wrapping and Unwrapping
This section specifies the algorithms for wrapping and unwrapping one This section specifies the algorithms for wrapping and unwrapping one
RC2 key with another RC2 key [RC2]. RC2 key with another RC2 key [RC2].
RC2 supports variable length keys. RC2 128-bit keys MUST be used as
key-encryption keys; however, the wrapped RC2 key MAY be of any size.
4.1 RC2 Key Wrap 4.1 RC2 Key Wrap
The RC2 key wrap algorithm encrypts a RC2 key with a RC2 key- The RC2 key wrap algorithm encrypts a RC2 key with a RC2 key-
encryption key. The RC2 key wrap algorithm is: encryption key. The RC2 key wrap algorithm is:
1. Let the RC2 key be called CEK, and let the length of CEK in 1. Let the RC2 key be called CEK, and let the length of CEK in
octets be called LENGTH. LENGTH is a single octet. octets be called LENGTH. LENGTH is a single octet.
2. Let LCEK = LENGTH || CEK. 2. Let LCEK = LENGTH || CEK.
3. Let LCEKPAD = LCEK || PAD. If the length of LCEK is a multiple 3. Let LCEKPAD = LCEK || PAD. If the length of LCEK is a multiple
of 8, the PAD has a length of zero. If the length of LCEK is of 8, the PAD has a length of zero. If the length of LCEK is
skipping to change at page 6, line 21 skipping to change at page 6, line 38
RC2ParameterVersion ::= INTEGER RC2ParameterVersion ::= INTEGER
The RC2 effective-key-bits (key size) greater than 32 and less than The RC2 effective-key-bits (key size) greater than 32 and less than
256 is encoded in the RC2ParameterVersion. For the effective-key- 256 is encoded in the RC2ParameterVersion. For the effective-key-
bits of 40, 64, and 128, the rc2ParameterVersion values are 160, 120, bits of 40, 64, and 128, the rc2ParameterVersion values are 160, 120,
and 58 respectively. These values are not simply the RC2 key length. and 58 respectively. These values are not simply the RC2 key length.
Note that the value 160 must be encoded as two octets (00 A0), Note that the value 160 must be encoded as two octets (00 A0),
because the one octet (A0) encoding represents a negative number. because the one octet (A0) encoding represents a negative number.
3.4 RC2 Key Wrap Example
This section contains a RC2 Key Wrap example. Intermediate values
corresponding to the named items in section 4.1 are given in
hexadecimal.
CEK: b70a 25fb c9d8 6a86 050c e0d7 11ea d4d9
KEK: fd04 fd08 0607 07fb 0003 feff fd02 fe05
LENGTH: 10
LCEK: 10b7 0a25 fbc9 d86a 8605 0ce0 d711 ead4 d9
PAD: 4845 cce7 fd12 50
LCEKPAD: 10b7 0a25 fbc9 d86a 8605 0ce0 d711 ead4
d948 45cc e7fd 1250
ICV: 0a6f f19f db40 4988
LCEKPADICV: 10b7 0a25 fbc9 d86a 8605 0ce0 d711 ead4
d948 45cc e7fd 1250 0a6f f19f db40 4988
IV: c7d9 0059 b29e 97f7
TEMP1: a01d a259 3793 1260 e48c 55f5 04ce 70b8
ac8c d79e ffe8 9932 9fa9 8a07 a31f f7a7
TEMP2: c7d9 0059 b29e 97f7 a01d a259 3793 1260
e48c 55f5 04ce 70b8 ac8c d79e ffe8 9932
9fa9 8a07 a31f f7a7
TEMP3: a7f7 1fa3 078a a99f 3299 8eff 9ed7 8cac
b870 ce04 f555 8ce4 6012 9337 59a2 1da0
f797 9eb2 5900 d9c7
RESULT: 70e6 99fb 5701 f783 3330 fb71 e87c 85a4
20bd c99a f05d 22af 5a0e 48d3 5f31 3898
6cba afb4 b28d 4f35
References References
3DES American National Standards Institute. ANSI X9.52-1998, 3DES American National Standards Institute. ANSI X9.52-1998,
Triple Data Encryption Algorithm Modes of Operation. 1998. Triple Data Encryption Algorithm Modes of Operation. 1998.
CMS Housley, R., "Cryptographic Message Syntax", RFC 2630, CMS Housley, R., "Cryptographic Message Syntax", RFC 2630,
June 1999. June 1999.
DES American National Standards Institute. ANSI X3.106, DES American National Standards Institute. ANSI X3.106,
"American National Standard for Information Systems - Data "American National Standard for Information Systems - Data
skipping to change at page 7, line 46 skipping to change at page 8, line 46
reviewed for use with Triple-DES and RC2, and they have not been reviewed for use with Triple-DES and RC2, and they have not been
reviewed for use with other encryption algorithms. Similarly, the reviewed for use with other encryption algorithms. Similarly, the
key wrap algorithms make use of CBC mode [MODES], and they have not key wrap algorithms make use of CBC mode [MODES], and they have not
been reviewed for use with other cryptographic modes. been reviewed for use with other cryptographic modes.
Acknowledgments Acknowledgments
This document is the result of contributions from many professionals. This document is the result of contributions from many professionals.
I appreciate the hard work of all members of the IETF S/MIME Working I appreciate the hard work of all members of the IETF S/MIME Working
Group. I extend a special thanks to Carl Ellison, Peter Gutmann, Bob Group. I extend a special thanks to Carl Ellison, Peter Gutmann, Bob
Jueneman, Don Johnson, and Burt Kaliski for their support in defining Jueneman, Don Johnson, Burt Kaliski, John Pawling, and Jim Schaad for
these algorithms. their support in defining these algorithms and generating this
specification.
Author Address Author Address
Russell Housley Russell Housley
RSA Laboratories RSA Laboratories
918 Spring Knoll Drive 918 Spring Knoll Drive
Herndon, VA 20170 Herndon, VA 20170
USA USA
rhousley@rsasecurity.com rhousley@rsasecurity.com
 End of changes. 

This html diff was produced by rfcdiff 1.25, available from http://www.levkowetz.com/ietf/tools/rfcdiff/