ftp.cc.uoc.gr
rfc3394
This is a purely informative rendering of an RFC that includes verified errata. This rendering may not be used as a reference.

The following 'Verified' errata have been incorporated in this document: EID 3671
Network Working Group                                          J. Schaad
Request for Comments: 3394                       Soaring Hawk Consulting
Category: Informational                                       R. Housley
                                                        RSA Laboratories
                                                          September 2002


         Advanced Encryption Standard (AES) Key Wrap Algorithm

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   The purpose of this document is to make the Advanced Encryption
   Standard (AES) Key Wrap algorithm conveniently available to the
   Internet community.  The United States of America has adopted AES as
   the new encryption standard.  The AES Key Wrap algorithm will
   probably be adopted by the USA for encryption of AES keys. The
   authors took most of the text in this document from the draft AES Key
   Wrap posted by NIST.

Table of Contents

   1. Introduction................................................  2
   2. Overview....................................................  2
   2.1 Notation and Definitions...................................  3
   2.2 Algorithms.................................................  4
   2.2.1 Key Wrap.................................................  4
   2.2.2 Key Unwrap...............................................  5
   2.2.3 Key Data Integrity -- the Initial Value..................  6
   2.2.3.1 Default Initial Value..................................  7
   2.2.3.2 Alternative Initial Values.............................  7
   3. Object Identifiers..........................................  8
   4. Test Vectors................................................  8
   4.1 Wrap 128 bits of Key Data with a 128-bit KEK...............  8
   4.2 Wrap 128 bits of Key Data with a 192-bit KEK............... 11
   4.3 Wrap 128 bits of Key Data with a 256-bit KEK............... 14
   4.4 Wrap 192 bits of Key Data with a 192-bit KEK............... 17
   4.5 Wrap 192 bits of Key Data with a 256-bit KEK............... 24
   4.6 Wrap 256 bits of Key Data with a 256-bit KEK............... 30

   5. Security Considerations..................................... 39
   6. References.................................................. 39
   7. Acknowledgments............................................. 39
   8. Authors' Addresses.......................................... 39
   9. Full Copyright Statement.................................... 40

1. Introduction

   NOTE: Most of the following text is taken from [AES-WRAP], and the
   assertions regarding the security of the AES Key Wrap algorithm are
   made by the US Government, not by the authors of this document.

   This specification is intended to satisfy the National Institute of
   Standards and Technology (NIST) Key Wrap requirement to:  Design a
   cryptographic algorithm called a Key Wrap that uses the Advanced
   Encryption Standard (AES) as a primitive to securely encrypt
   plaintext key(s) with any associated integrity information and data,
   such that the combination could be longer than the width of the AES
   block size (128-bits).  Each ciphertext bit should be a highly non-
   linear function of each plaintext bit, and (when unwrapping) each
   plaintext bit should be a highly non-linear function of each
   ciphertext bit.  It is sufficient to approximate an ideal
   pseudorandom permutation to the degree that exploitation of
   undesirable phenomena is as unlikely as guessing the AES engine key.

   This key wrap algorithm needs to provide ample security to protect
   keys in the context of prudently designed key management
   architecture.

   Throughout this document, any data being wrapped will be referred to
   as the key data.  It makes no difference to the algorithm whether the
   data being wrapped is a key; in fact there is often good reason to
   include other data with the key, to wrap multiple keys together, or
   to wrap data that isn't strictly a key.  So, the term "key data" is
   used broadly to mean any data being wrapped, but particularly keys,
   since this is primarily a key wrap algorithm.  The key used to do the
   wrapping will be referred to as the key-encryption key (KEK).

   In this document a KEK can be any valid key supported by the AES
   codebook.  That is, a KEK can be a 128-bit key, a 192-bit key, or a
   256-bit key.

2. Overview

   The AES key wrap algorithm is designed to wrap or encrypt key data.
   The key wrap operates on blocks of 64 bits.  Before being wrapped,
   the key data is parsed into n blocks of 64 bits.

   The only restriction the key wrap algorithm places on n is that n be
   at least two.  (For key data with length less than or equal to 64
   bits, the constant field used in this specification and the key data
   form a single 128-bit codebook input making this key wrap
   unnecessary.)  The key wrap algorithm accommodates all supported AES
   key sizes.  However, other cryptographic values often need to be
   wrapped.  One such value is the seed of the random number generator
   for DSS.  This seed value requires n to be greater than four.
   Undoubtedly other values require this type of protection. Therefore,
   no upper bound is imposed on n.

   The AES key wrap can be configured to use any of the three key sizes
   supported by the AES codebook.  The choice of a key size affects the
   overall security provided by the key wrap, but it does not alter the
   description of the key wrap algorithm.  Therefore, in the description
   that follows, the key wrap is described generically; no key size is
   specified for the KEK.

2.1 Notation and Definitions

   The following notation is used in the description of the key wrapping
   algorithms:

      AES(K, W)     Encrypt W using the AES codebook with key K
      AES-1(K, W)   Decrypt W using the AES codebook with key K
      MSB(j, W)     Return the most significant j bits of W
      LSB(j, W)     Return the least significant j bits of W
      B1 ^ B2       The bitwise exclusive or (XOR) of B1 and B2
      B1 | B2       Concatenate B1 and B2
      K             The key-encryption key K
      n             The number of 64-bit key data blocks
      s             The number of steps in the wrapping process, s = 6n
      P[i]          The ith plaintext key data block
      C[i]          The ith ciphertext data block
      A             The 64-bit integrity check register
      R[i]          An array of 64-bit registers where
                       i = 0, 1, 2, ..., n
      A[t], R[i][t] The contents of registers A and R[i] after encryption
                       step t.
      IV            The 64-bit initial value used during the wrapping
                       process.

   In the key wrap algorithm, the concatenation function will be used to
   concatenate 64-bit quantities to form the 128-bit input to the AES
   codebook.  The extraction functions will be used to split the 128-bit
   output from the AES codebook into two 64-bit quantities.

2.2 Algorithms

   The specification of the key wrap algorithm requires the use of the
   AES codebook [AES].  The next three sections will describe the key
   wrap algorithm, the key unwrap algorithm, and the inherent data
   integrity check.

2.2.1 Key Wrap

   The inputs to the key wrapping process are the KEK and the plaintext
   to be wrapped.  The plaintext consists of n 64-bit blocks, containing
   the key data being wrapped.  The key wrapping process is described
   below.

   Inputs:      Plaintext, n 64-bit values {P1, P2, ..., Pn}, and
                Key, K (the KEK).
   Outputs:     Ciphertext, (n+1) 64-bit values {C0, C1, ..., Cn}.

   1) Initialize variables.

       Set A0 to an initial value (see 2.2.3)
       For i = 1 to n
            R[0][i] = P[i]

   2) Calculate intermediate values.

       For t = 1 to s, where s = 6n
           A[t] = MSB(64, AES(K, A[t-1] | R[t-1][1])) ^ t
           For i = 1 to n-1
               R[t][i] = R[t-1][i+1]
           R[t][n] = LSB(64, AES(K, A[t-1] | R[t-1][1]))

   3) Output the results.

       Set C[0] = A[t]
       For i = 1 to n
           C[i] = R[t][i]

   An alternative description of the key wrap algorithm involves
   indexing rather than shifting.  This approach allows one to calculate
   the wrapped key in place, avoiding the rotation in the previous
   description.  This produces identical results and is more easily
   implemented in software.

   Inputs:  Plaintext, n 64-bit values {P1, P2, ..., Pn}, and
            Key, K (the KEK).
   Outputs: Ciphertext, (n+1) 64-bit values {C0, C1, ..., Cn}.

   1) Initialize variables.

       Set A = IV, an initial value (see 2.2.3)
       For i = 1 to n
           R[i] = P[i]

   2) Calculate intermediate values.

       For j = 0 to 5
           For i=1 to n
               B = AES(K, A | R[i])
               A = MSB(64, B) ^ t where t = (n*j)+i
               R[i] = LSB(64, B)

   3) Output the results.

       Set C[0] = A
       For i = 1 to n
           C[i] = R[i]

2.2.2 Key Unwrap

   The inputs to the unwrap process are the KEK and (n+1) 64-bit blocks
   of ciphertext consisting of previously wrapped key.  It returns n
   blocks of plaintext consisting of the n 64-bit blocks of the
   decrypted key data.

   Inputs:  Ciphertext, (n+1) 64-bit values {C0, C1, ..., Cn}, and
           Key, K (the KEK).
   Outputs: Plaintext, n 64-bit values {P1, P2, ..., Pn}.

   1) Initialize variables.

       Set A[s] = C[0] where s = 6n
       For i = 1 to n
           R[s][i] = C[i]

   2) Calculate the intermediate values.

       For t = s to 1
           A[t-1] = MSB(64, AES-1(K, ((A[t] ^ t) | R[t][n]))
           R[t-1][1] = LSB(64, AES-1(K, ((A[t]^t) | R[t][n]))
           For i = 2 to n
               R[t-1][i] = R[t][i-1]

   3) Output the results.

       If A[0] is an appropriate initial value (see 2.2.3),
       Then
           For i = 1 to n
               P[i] = R[0][i]
       Else
           Return an error

   The unwrap algorithm can also be specified as an index based
   operation, allowing the calculations to be carried out in place.
   Again, this produces the same results as the register shifting
   approach.

   Inputs:  Ciphertext, (n+1) 64-bit values {C0, C1, ..., Cn}, and
            Key, K (the KEK).
   Outputs: Plaintext, n 64-bit values {P0, P1, K, Pn}.

   1) Initialize variables.

       Set A = C[0]
       For i = 1 to n
           R[i] = C[i]

   2) Compute intermediate values.

       For j = 5 to 0
           For i = n to 1
               B = AES-1(K, (A ^ t) | R[i]) where t = n*j+i
               A = MSB(64, B)
               R[i] = LSB(64, B)

   3) Output results.

   If A is an appropriate initial value (see 2.2.3),
   Then
       For i = 1 to n
           P[i] = R[i]
   Else
       Return an error

2.2.3 Key Data Integrity -- the Initial Value

   The initial value (IV) refers to the value assigned to A[0] in the
   first step of the wrapping process.  This value is used to obtain an
   integrity check on the key data.  In the final step of the unwrapping
   process, the recovered value of A[0] is compared to the expected

   value of A[0].  If there is a match, the key is accepted as valid,
   and the unwrapping algorithm returns it.  If there is not a match,
   then the key is rejected, and the unwrapping algorithm returns an
   error.

   The exact properties achieved by this integrity check depend on the
   definition of the initial value.  Different applications may call for
   somewhat different properties; for example, whether there is need to
   determine the integrity of key data throughout its lifecycle or just
   when it is unwrapped.  This specification defines a default initial
   value that supports integrity of the key data during the period it is
   wrapped (2.2.3.1).  Provision is also made to support alternative
   initial values (in 2.2.3.2).

2.2.3.1 Default Initial Value

   The default initial value (IV) is defined to be the hexadecimal
   constant:

       A[0] = IV = A6A6A6A6A6A6A6A6

   The use of a constant as the IV supports a strong integrity check on
   the key data during the period that it is wrapped.  If unwrapping
   produces A[0] = A6A6A6A6A6A6A6A6, then the chance that the key data
   is corrupt is 2^-64.  If unwrapping produces A[0] equal to any other value, 
EID 3671 (Verified) is as follows:

Section: 2.2.3.1

Original Text:

If unwrapping produces A[0] any other value,

Corrected Text:

If unwrapping produces A[0] equal to any other value,
Notes:
This resembles a copy-paste typo, where the last portion of "If unwrapping produces A[0]" was not removed in the second of two sentences.

I edited this based on comments from the authors.
then the unwrap must return an error and not return any key data. 2.2.3.2 Alternative Initial Values When the key wrap is used as part of a larger key management protocol or system, the desired scope for data integrity may be more than just the key data or the desired duration for more than just the period that it is wrapped. Also, if the key data is not just an AES key, it may not always be a multiple of 64 bits. Alternative definitions of the initial value can be used to address such problems. NIST will define alternative initial values in future key management publications as needed. In order to accommodate a set of alternatives that may evolve over time, key wrap implementations that are not application-specific will require some flexibility in the way that the initial value is set and tested. 3. Object Identifiers NIST has assigned the following object identifiers to identify the key wrap algorithm with the default initial value specified in 2.2.3.1. One object identifier is assigned for use with each of the KEK AES key sizes. aes OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101) csor(3) nistAlgorithm(4) 1 } id-aes128-wrap OBJECT IDENTIFIER ::= { aes 5 } id-aes192-wrap OBJECT IDENTIFIER ::= { aes 25 } id-aes256-wrap OBJECT IDENTIFIER ::= { aes 45 } 4. Test Vectors The examples in this section were generated using the index-based implementation of the key wrap algorithm. The use of this approach allows a straightforward software implementation of the key wrap algorithm. 4.1 Wrap 128 bits of Key Data with a 128-bit KEK Input: KEK: 000102030405060708090A0B0C0D0E0F Key Data: 00112233445566778899AABBCCDDEEFF Wrap: Step t A R1 R2 1 In A6A6A6A6A6A6A6A6 0011223344556677 8899AABBCCDDEEFF Enc F4740052E82A2251 74CE86FBD7B805E7 8899AABBCCDDEEFF XorT F4740052E82A2250 74CE86FBD7B805E7 8899AABBCCDDEEFF 2 In F4740052E82A2250 74CE86FBD7B805E7 8899AABBCCDDEEFF Enc 06BA4EBDE7768D0B 74CE86FBD7B805E7 D132EE38147E76F8 XorT 06BA4EBDE7768D09 74CE86FBD7B805E7 D132EE38147E76F8 3 In 06BA4EBDE7768D09 74CE86FBD7B805E7 D132EE38147E76F8 Enc FC967627BE937208 FE6E8D679C5D3460 D132EE38147E76F8 XorT FC967627BE93720B FE6E8D679C5D3460 D132EE38147E76F8 4 In FC967627BE93720B FE6E8D679C5D3460 D132EE38147E76F8 Enc 5896EA9028EE203B FE6E8D679C5D3460 07B2BD973E36A6FC XorT 5896EA9028EE203F FE6E8D679C5D3460 07B2BD973E36A6FC 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 4.2 Wrap 128 bits of Key Data with a 192-bit KEK Input: KEK: 000102030405060708090A0B0C0D0E0F1011121314151617 Key Data: 00112233445566778899AABBCCDDEEFF Wrap: Step t A R1 R21 In A6A6A6A6A6A6A6A6 0011223344556677 8899AABBCCDDEEFF Enc DFE8FD5D1A3786A7 351D385096CCFB29 8899AABBCCDDEEFF XorT DFE8FD5D1A3786A6 351D385096CCFB29 8899AABBCCDDEEFF 2 In DFE8FD5D1A3786A6 351D385096CCFB29 8899AABBCCDDEEFF Enc 9D9B32B9ED742E02 351D385096CCFB29 51F22F3286758A2D XorT 9D9B32B9ED742E00 351D385096CCFB29 51F22F3286758A2D 3 In 9D9B32B9ED742E00 351D385096CCFB29 51F22F3286758A2D Enc 7B8E343CA51CF8AB BC164F51E20CC983 51F22F3286758A2D XorT 7B8E343CA51CF8A8 BC164F51E20CC983 51F22F3286758A2D 4 In 7B8E343CA51CF8A8 BC164F51E20CC983 51F22F3286758A2D Enc 02A97C5897140595 BC164F51E20CC983 05FC2D8F8FF4B919 XorT 02A97C5897140591 BC164F51E20CC983 05FC2D8F8FF4B919 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 4.3 Wrap 128 bits of Key Data with a 256-bit KEK Input: KEK:000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F Key Data: 00112233445566778899AABBCCDDEEFF Wrap: Step t A R1 R2 1 In A6A6A6A6A6A6A6A6 0011223344556677 8899AABBCCDDEEFF Enc 794314D454E3FDE1 F661BD9F31FBFA31 8899AABBCCDDEEFF XorT 794314D454E3FDE0 F661BD9F31FBFA31 8899AABBCCDDEEFF 2 In 794314D454E3FDE0 F661BD9F31FBFA31 8899AABBCCDDEEFF Enc D450EA5C5BBCB561 F661BD9F31FBFA31 F60E0CDB7F429FE8 XorT D450EA5C5BBCB563 F661BD9F31FBFA31 F60E0CDB7F429FE8 3 In D450EA5C5BBCB563 F661BD9F31FBFA31 F60E0CDB7F429FE8 Enc 85DBDF1879D5C0A5 5602001BFA07AD8B F60E0CDB7F429FE8 XorT 85DBDF1879D5C0A6 5602001BFA07AD8B F60E0CDB7F429FE8 4 In 85DBDF1879D5C0A6 5602001BFA07AD8B F60E0CDB7F429FE8 Enc 738C291128B7226D 5602001BFA07AD8B 58924F777C3F678C XorT 738C291128B72269 5602001BFA07AD8B 58924F777C3F678C 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 4.4 Wrap 192 bits of Key Data with a 192-bit KEK Input: KEK: 000102030405060708090A0B0C0D0E0F1011121314151617 Key Data: 00112233445566778899AABBCCDDEEFF0001020304050607 Wrap: Step t A/R3 R1 R2 1 In A6A6A6A6A6A6A6A6 0011223344556677 8899AABBCCDDEEFF 0001020304050607 Enc DFE8FD5D1A3786A7 351D385096CCFB29 8899AABBCCDDEEFF 0001020304050607 XorT DFE8FD5D1A3786A6 351D385096CCFB29 8899AABBCCDDEEFF 0001020304050607 2 In DFE8FD5D1A3786A6 351D385096CCFB29 8899AABBCCDDEEFF 0001020304050607 Enc 9D9B32B9ED742E02 351D385096CCFB29 51F22F3286758A2D 0001020304050607 XorT 9D9B32B9ED742E00 351D385096CCFB29 51F22F3286758A2D 0001020304050607 3 In 9D9B32B9ED742E00 351D385096CCFB29 51F22F3286758A2D 0001020304050607 Enc 2C8E19A519025B7C 351D385096CCFB29 51F22F3286758A2D FF540E514DE120A3 XorT 2C8E19A519025B7F 351D385096CCFB29 51F22F3286758A2D FF540E514DE120A3 4 In 2C8E19A519025B7F 351D385096CCFB29 51F22F3286758A2D FF540E514DE120A3 Enc E727C7BDF822602E A08DAA041D17BBBA 51F22F3286758A2D FF540E514DE120A3 XorT E727C7BDF822602A A08DAA041D17BBBA 51F22F3286758A2D FF540E514DE120A3 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 4.5 Wrap 192 bits of Key Data with a 256-bit KEK Input: KEK: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F Key Data: 00112233445566778899AABBCCDDEEFF0001020304050607 Wrap: Step t A/R3 R1 R2 1 In A6A6A6A6A6A6A6A6 0011223344556677 8899AABBCCDDEEFF 0001020304050607 Enc 794314D454E3FDE1 F661BD9F31FBFA31 8899AABBCCDDEEFF 0001020304050607 XorT 794314D454E3FDE0 F661BD9F31FBFA31 8899AABBCCDDEEFF 0001020304050607 2 In 794314D454E3FDE0 F661BD9F31FBFA31 8899AABBCCDDEEFF 0001020304050607 Enc D450EA5C5BBCB561 F661BD9F31FBFA31 F60E0CDB7F429FE8 0001020304050607 XorT D450EA5C5BBCB563 F661BD9F31FBFA31 F60E0CDB7F429FE8 0001020304050607 3 In D450EA5C5BBCB563 F661BD9F31FBFA31 F60E0CDB7F429FE8 0001020304050607 Enc 9DF8F5405FBC00C1 F661BD9F31FBFA31 F60E0CDB7F429FE8 6CA405593A3B5154 XorT 9DF8F5405FBC00C2 F661BD9F31FBFA31 F60E0CDB7F429FE8 6CA405593A3B5154 4 In 9DF8F5405FBC00C2 F661BD9F31FBFA31 F60E0CDB7F429FE8 6CA405593A3B5154 Enc F1D28EA6295891EC 0CC86A4D9B9C6A31 F60E0CDB7F429FE8 6CA405593A3B5154 XorT F1D28EA6295891E8 0CC86A4D9B9C6A31 F60E0CDB7F429FE8 6CA405593A3B5154 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 4.6 Wrap 256 bits of Key Data with a 256-bit KEK Input: KEK: 000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F Key Data: 00112233445566778899AABBCCDDEEFF000102030405060708090A0B0C0D0E0F Wrap: Step t A/R3 R1/R4 R2 1 In A6A6A6A6A6A6A6A6 0011223344556677 8899AABBCCDDEEFF 0001020304050607 08090A0B0C0D0E0F Enc 794314D454E3FDE1 F661BD9F31FBFA31 8899AABBCCDDEEFF 0001020304050607 08090A0B0C0D0E0F XorT 794314D454E3FDE0 F661BD9F31FBFA31 8899AABBCCDDEEFF 0001020304050607 08090A0B0C0D0E0F 2 In 794314D454E3FDE0 F661BD9F31FBFA31 8899AABBCCDDEEFF 0001020304050607 08090A0B0C0D0E0F Enc D450EA5C5BBCB561 F661BD9F31FBFA31 F60E0CDB7F429FE8 0001020304050607 08090A0B0C0D0E0F XorT D450EA5C5BBCB563 F661BD9F31FBFA31 F60E0CDB7F429FE8 0001020304050607 08090A0B0C0D0E0F 3 In D450EA5C5BBCB563 F661BD9F31FBFA31 F60E0CDB7F429FE8 0001020304050607 08090A0B0C0D0E0F Enc 9DF8F5405FBC00C1 F661BD9F31FBFA31 F60E0CDB7F429FE8 6CA405593A3B5154 08090A0B0C0D0E0F XorT 9DF8F5405FBC00C2 F661BD9F31FBFA31 F60E0CDB7F429FE8 6CA405593A3B5154 08090A0B0C0D0E0F 4 In 9DF8F5405FBC00C2 F661BD9F31FBFA31 F60E0CDB7F429FE8 6CA405593A3B5154 08090A0B0C0D0E0F Enc 564408FDD0DD2EA4 F661BD9F31FBFA31 F60E0CDB7F429FE8 6CA405593A3B5154 E5923CB9FDB56FBC XorT 564408FDD0DD2EA0 F661BD9F31FBFA31 F60E0CDB7F429FE8 6CA405593A3B5154 E5923CB9FDB56FBC 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 5. Security Considerations The key wrap algorithm includes a strong integrity check on the key data. If unwrapping produces the expected check value in A[0], then the chance that the key data is corrupt is 2^-64. If unwrapping produces an unexpected value, then the algorithm implementation MUST return an error, and it MUST NOT return any key data. Implementations must protect the KEK from disclosure. Compromise of the KEK may result in the disclosure of all key data protected with that KEK. 6. References AES National Institute of Standards and Technology. FIPS Pub 197: Advanced Encryption Standard (AES). 26 November 2001. AES-WRAP National Institute of Standards and Technology. AES Key Wrap Specification. 17 November 2001. [http://csrc.nist.gov/encryption/kms/key-wrap.pdf] 7. Acknowledgments Most of the text in this document is taken from [AES-WRAP]. The authors of that document are responsible for the development of the AES key wrap algorithm. 8. Authors' Addresses Jim Schaad Soaring Hawk Consulting EMail: jimsch@exmsft.com Russell Housley RSA Laboratories 918 Spring Knoll Drive Herndon, VA 20170 USA EMail: rhousley@rsasecurity.com 9. Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others provided that the above copyright notice and this paragraph are included on all such copies. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. 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