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Versions: (draft-ietf-kitten-aes-cbc-hmac-sha2) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 8009

Network Working Group                                          K. Burgin
Internet Draft                                  National Security Agency
Intended Status: Informational                                   M. Peck
Expires: December 30, 2013                         The MITRE Corporation
                                                           June 28, 2013

              AES Encryption with HMAC-SHA2 for Kerberos 5
                 draft-ietf-kitten-aes-cts-hmac-sha2-01

Abstract

   This document specifies two encryption types and two corresponding
   checksum types for Kerberos 5.  The new types use AES in CTS mode
   (CBC mode with ciphertext stealing) for confidentiality and HMAC with
   a SHA-2 hash for integrity.

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
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   This Internet-Draft will expire on December 30, 2013.

Copyright and License Notice

   Copyright (c) 2013 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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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Protocol Key Representation  . . . . . . . . . . . . . . . . .  3
   3.  Key Generation from Pass Phrases . . . . . . . . . . . . . . .  3
   4.  Key Derivation Function  . . . . . . . . . . . . . . . . . . .  4
   5.  Kerberos Algorithm Protocol Parameters . . . . . . . . . . . .  5
   6.  Checksum Parameters  . . . . . . . . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
     8.1.  Random Values in Salt Strings  . . . . . . . . . . . . . .  9
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Appendix A.  Test Vectors  . . . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15



































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1.  Introduction

   This document defines two encryption types and two corresponding
   checksum types for Kerberos 5 using AES with 128-bit or 256-bit keys.
   To avoid ciphertext expansion, we use the CBC-CS3 variant to CBC mode
   defined in [SP800-38A+] (this mode is also referred to as CTS).  The
   new types conform to the framework specified in [RFC3961], but do not
   use the simplified profile.

   Note that [SP800-38A+] requires the plaintext length to be greater
   than the block size, so the encryption types have two cases.

   The encryption and checksum types defined in this document are
   intended to support NSA's Suite B Profile for Kerberos [suiteb-
   kerberos] which requires the use of SHA-256 or SHA-384 as the hash
   algorithm.  Differences between the encryption and checksum types
   defined in this document and existing Kerberos encryption and
   checksum types are:

   *  The pseudorandom function used by PBKDF2 is HMAC-SHA-256 or HMAC-
      SHA-384.

   *  A key derivation function from [SP800-108] which uses the SHA-256
      or SHA-384 hash algorithm is used to produce keys for encryption,
      integrity protection, and checksum operations.

   *  The IV used during content encryption is sent as part of the
      ciphertext, instead of using a confounder. This saves one
      encryption and decryption operation per message.

   *  The HMAC is calculated over the AES output, instead of being
      calculated over the plaintext.  This allows the message receiver
      to verify the integrity of the message before decrypting the
      message.

   *  The HMAC algorithm uses the SHA-256 or SHA-384 hash algorithm for
      integrity protection and checksum operations.

2.  Protocol Key Representation

   The AES key space is dense, so we can use random or pseudorandom
   octet strings directly as keys.  The byte representation for the key
   is described in [FIPS197], where the first bit of the bit string is
   the high bit of the first byte of the byte string (octet string).

3.  Key Generation from Pass Phrases

   The pseudorandom function used by PBKDF2 will be the SHA-256 or SHA-



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   384 HMAC of the passphrase and salt. If the enctype is "aes128-cts-
   hmac-sha256-128", then HMAC-SHA-256 is used as the PRF.  If the
   enctype is "aes256-cts-hmac-sha384-192", then HMAC-SHA-384 is used as
   the PRF.

   The final key derivation step uses the algorithm KDF-HMAC-SHA2
   defined below in Section 4.

   If no string-to-key parameters are specified, the default number of
   iterations is raised to 32,768.

   To ensure that different long-term keys are used with different
   enctypes, we prepend the enctype name to the salt string, separated
   by a null byte.  The enctype name is "aes128-cts-hmac-sha256-128" or
   "aes256-cts-hmac-sha384-192" (without the quotes). The user's long-
   term key is derived as follows

     saltp = enctype-name | 0x00 | salt
     tkey = random-to-key(PBKDF2(passphrase, saltp,
                              iter_count, keylength))
     key = KDF-HMAC-SHA2(tkey, "kerberos") where "kerberos" is the
           byte string {0x6b65726265726f73}.

   where the pseudorandom function used by PBKDF2 is HMAC-SHA-256 when
   the enctype is "aes128-cts-hmac-sha256-128" and HMAC-SHA-384 when the
   enctype is "aes256-cts-hmac-sha384-192", the value for keylength is
   the AES key length, and the algorithm KDF-HMAC-SHA2 is defined in
   Section 4.


4.  Key Derivation Function

   We use a key derivation function from Section 5.1 of [SP800-108]
   which uses the HMAC algorithm as the PRF.  The counter i is expressed
   as four octets in big-endian order.  The length of the output key in
   bits (denoted as k) is also represented as four octets in big-endian
   order.  The "Label" input to the KDF is the usage constant supplied
   to the key derivation function, and the "Context" input is null.
   Each application of the KDF only requires a single iteration of the
   PRF, so n = 1 in the notation of [SP800-108].

   In the following summary, | indicates concatenation.  The random-to-
   key function is the identity function, as defined in Section 3.  The
   k-truncate function is defined in [RFC3961], Section 5.1.

   When the encryption type is aes128-cts-hmac-sha256-128, the output
   key length k is 128 bits for all applications of KDF-HMAC-SHA2(key,
   constant) which is computed as follows:



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     K1 = HMAC-SHA-256(key, 00 00 00 01 | constant | 0x00 | 00 00 00 80)
     KDF-HMAC-SHA2(key, constant) = random-to-key(k-truncate(K1))

   When the encryption type is aes256-cts-hmac-sha384-192, the output
   key length k is 256 bits when computing the base-key and Ke, and the
   output key length k is 192 bits when deriving Kc and Ki.  KDF-HMAC-
   SHA2(key, constant) is computed as follows:

     If deriving Kc or Ki (the constant ends with 0x99 or 0x55):
     k = 192
     K1 = HMAC-SHA-384(key, 00 00 00 01 | constant | 0x00 | 00 00 00 C0)
     KDF-HMAC-SHA2(key, constant) = random-to-key(k-truncate(K1))

     Otherwise (if deriving Ke or deriving the base-key from a
                passphrase as described in Section 3):
     k = 256
     K1 = HMAC-SHA-384(key, 00 00 00 01 | constant | 0x00 | 00 00 01 00)
     KDF-HMAC-SHA2(key, constant) = random-to-key(k-truncate(K1))

   The constants used for key derivation are the same as those used in
   the simplified profile.

5.  Kerberos Algorithm Protocol Parameters

   In cases where the plaintext length is greater than the block size:

      Each encryption will use a 16-octet nonce generated at random by
      the message originator.  The initialization vector (IV) used by
      AES is obtained by xoring the random nonce with the cipherstate.

      The ciphertext is the concatenation of the random nonce, the
      output of AES in CBC-CS3 mode, and the HMAC of the nonce
      concatenated with the AES output.  The HMAC is computed using
      either SHA-256 or SHA-384.  The output of SHA-256 is truncated to
      128 bits and the output of SHA-384 is truncated to 192 bits.
      Sample test vectors are given in Appendix A.

      Decryption is performed by removing the HMAC, verifying the HMAC
      against the remainder, and then decrypting the remainder if the
      HMAC is correct.

   In cases where the plaintext length is less than or equal to the
   block size, a different algorithm is specified.

      Each encryption will use a 16-octet nonce generated at random by
      the message originator.  The initialization vector (IV) used by
      AES is obtained by xoring the random nonce with the cipherstate.




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      The plaintext is padded with zeros so the length of the result is
      one block length (no zeros are added if the plaintext length
      equals the block length).  The padded plaintext is xored with the
      IV, then encrypted using AES in ECB mode.  The output of AES is
      split into two parts, so that the length of the first part equals
      the length of the unpadded plaintext.  The nonce is also split
      into two parts, so that the length of the first part equals the
      length of the unpadded plaintext.

      The ciphertext is the concatenation of the first part of the
      random nonce, the second part of the AES output followed by the
      first part of the AES output, and the HMAC of the concatenation of
      the first part of the random nonce, the second part of the AES
      output followed by the first part of the AES output.  The HMAC is
      computed using either SHA-256 or SHA-384.  The output of SHA-256
      is truncated to 128 bits and the output of SHA-384 is truncated to
      192 bits. Sample test vectors are given in Appendix A.

      Decryption is performed by first removing the HMAC, and verifying
      the HMAC against the remainder.  If the HMAC is correct, separate
      the remainder into N' and C' by taking the first 16 bytes as N',
      and the following bytes as C'.  Split N' into two parts, so that
      the length of the first part equals the length of C'.  Decrypt the
      concatenation of C' with the second part of N' using ECB mode to
      get a value P' whose length is one block length.  The nonce is
      recovered by taking the concatenation of the first part of N' with
      the second part of P' xored with the cipherState (where again, the
      length of the first part equals the length of C').  The IV is
      recovered as the nonce xored with cipherState, and the plaintext
      is recovered as the first part of P' xored with the IV.

   The following parameters apply to the encryption types aes128-cts-
   hmac-sha256-128 and aes256-cts-hmac-sha384-192.

   protocol key format: as defined in Section 2.

   specific key structure: three protocol-format keys: { Kc, Ke, Ki }.

   required checksum mechanism: as defined in Section 6.

   key-generation seed length: key size (128 or 256 bits).

   string-to-key function: as defined in Section 3.

   default string-to-key parameters: 00 00 80 00.

   random-to-key function: identity function.




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   key-derivation function: KDF-HMAC-SHA2 as defined in Section 4.  The
   key usage number is expressed as four octets in big-endian order.

   Kc = KDF-HMAC-SHA2(base-key, usage | 0x99)
   Ke = KDF-HMAC-SHA2(base-key, usage | 0xAA)
   Ki = KDF-HMAC-SHA2(base-key, usage | 0x55)

   cipherState: a 128-bit random nonce.

   initial cipherState: all bits zero.

   encryption function: as follows.  When the plaintext length is
   greater than the block size, CTS mode is used. When the plaintext
   is less than or equal to the block size, ECB mode is used.

   h = size of truncated HMAC
   E() = encryption function
   D() = decryption function
   c = block size of the encryption algorithm
   L(x) = length of x
   < = less-than operator; true == 1, false == 0
   zeroblock = one block (length c) of zeros
   o[start:len] = sub-string operation returning the substring of
                  length len of string o starting at byte start
                  (zero-based)

   encryption function:
      N = random nonce of length 128 bits
      IV = N XOR cipherState
      if (L(P) > c)
          PC = 0
          P' = P
          C = E(Ke, P', IV)
              // using CBC-CS3-Encrypt defined
              // in [SP800-38A+]
          N' = N
          C' = C
      else
          PC = c - L(P)
          P' = P | zeroblock[0:PC]
          C = E(Ke, P' XOR IV)
              // using ECB mode
          N' = N[0:c - PC] | C[c - PC:PC]
          C' = C[0:c - PC]
      H = HMAC(Ki, N' | C')
      ciphertext =  N' | C' | H[1..h]
      cipherState = N




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   decryption function:
      (N', C', H) = ciphertext
      if (H != HMAC(Ki, N' | C')[1..h])
          stop, report error

      if (L(C') > c)
          // Not short-plaintext
          IV = N' XOR cipherState
          P = D(Ke, C', IV)
              // using CBC-CS3-Decrypt defined
              // in [SP800-38A+]
          cipherState = N'
          stop, output P, success
      else
      // Short plaintext
      PC = c - L(C')
      C = C' | N'[c - PC:PC]
      P' = D(Ke, C)
           // using ECB mode

      // P' here == (P | zeroblock[0:PC]) XOR IV
      // so IV[c - PC:PC] == P'[c - PC:PC]
      // In the non-short-pt case we'd recover
      // IV as N XOR cipherState, but here we only know
      // a head of N and tail of IV.

      N = N'[0:c -PC] | (P' XOR cipherState)[c - PC:PC]
      IV = N XOR cipherState
      P = (P' XOR IV)[0:PC]
      cipherState = N
      stop, output P, success

   pseudo-random function:
      Kp  = KDF-HMAC-SHA2(protocol-key, "prf")
      PRF = HMAC(Kp, octet-string)

6.  Checksum Parameters

   The following parameters apply to the checksum types hmac-sha256-128-
   aes128 and hmac-sha384-192-aes256, which are the associated checksums
   for aes128-cts-hmac-sha256-128 and aes256-cts-hmac-sha384-192,
   respectively.

   associated cryptosystem: AES-128-CTS or AES-256-CTS as appropriate

   get_mic: HMAC(Kc, message)[1..h]

   verify_mic: get_mic and compare



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7.  IANA Considerations

   IANA is requested to assign:

   Encryption type numbers for aes128-cts-hmac-sha256-128 and
   aes256-cts-hmac-sha384-192 in the Kerberos Encryption Type Numbers
   registry.

      Etype   encryption type              Reference
      -----   ---------------              ---------
      TBD1    aes128-cts-hmac-sha256-128   [this document]
      TBD2    aes256-cts-hmac-sha384-192   [this document]

   Checksum type numbers for hmac-sha256-128-aes128 and hmac-sha384-192-
   aes256 in the Kerberos Checksum Type Numbers registry.

      Sumtype   Checksum type            Size   Reference
      -------   -------------            ----   ---------
      TBD3      hmac-sha256-128-aes128   16     [this document]
      TBD4      hmac-sha384-192-aes256   24     [this document]

8.  Security Considerations

   This specification requires implementations to generate random
   values.  The use of inadequate pseudo-random number generators
   (PRNGs) can result in little or no security.  The generation of
   quality random numbers is difficult.  NIST Special Publication 800-90
   [SP800-90] and [RFC4086] offer random number generation guidance.

   This document specifies a mechanism for generating keys from pass
   phrases or passwords.  The salt and iteration count resist brute
   force and dictionary attacks, however, it is still important to
   choose or generate strong passphrases.

8.1.  Random Values in Salt Strings

   NIST guidance in Section 5.1 of [SP800-132] requires the salt used as
   input to the PBKDF to contain at least 128 bits of random.  Some
   known issues with including random values in Kerberos encryption type
   salt strings are:

   *  Cross-realm TGTs are currently managed by entering the same
      password at two KDCs to get the same keys.  If each KDC uses a
      random salt, they won't have the same keys.

   *  The string-to-key function as defined in [RFC3961] requires the
      salt to be valid UTF-8 strings.  Not every 128-bit random string
      will be valid UTF-8.



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   *  Current implementations of password history checking will not
      work.

   *  ktutil's add_entry command assumes the default salt.

9.  References

9.1.  Normative References

   [RFC3961]    Raeburn, K., "Encryption and Checksum Specifications for
                Kerberos 5", RFC 3961, February 2005.

   [RFC4086]    Eastlake 3rd, D., Schiller, J., and S. Crocker,
                "Randomness Requirements for Security", BCP 106,
                RFC 4086, June 2005.

   [FIPS197]    National Institute of Standards and Technology,
                "Advanced Encryption Standard (AES)", FIPS PUB 197,
                November 2001.

9.2.  Informative References

   [SP800-38A+] National Institute of Standards and Technology,
                "Recommendation for Block Cipher Modes of Operation:
                Three Variants of Ciphertext Stealing for CBC Mode",
                Addendum to NIST Special Publication 800-38A, October
                2010.

   [SP800-90]   National Institute of Standards and Technology,
                Recommendation for Random Number Generation Using
                Deterministic Random Bit Generators (Revised), NIST
                Special Publication 800-90, March 2007.

   [SP800-108]  National Institute of Standards and Technology,
                "Recommendation for Key Derivation Using Pseudorandom
                Functions", NIST Special Publication 800-108, October
                2009.

   [SP800-132]  National Institute of Standards and Technology,
                "Recommendation for Password-Based Key Derivation, Part
                1: Storage Applications", NIST Special Publication 800-
                132, June 2010.

   [suiteb-kerberos]
                Burgin, K. and K. Igoe, "Suite B Profile for
                Kerberos 5", internet-draft draft-burgin-kerberos-
                suiteb-01, 2012.




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Appendix A.  Test Vectors

   Sample results for string-to-key conversion:
   --------------------------------------------

   Iteration count = 32768
   Pass phrase = "password"
   Saltp for creating 128-bit master key:
      61 65 73 31 32 38 2D 63 74 73 2D 68 6D 61 63 2D
      73 68 61 32 35 36 2D 31 32 38 00 10 DF 9D D7 83
      E5 BC 8A CE A1 73 0E 74 35 5F 61 41 54 48 45 4E
      41 2E 4D 49 54 2E 45 44 55 72 61 65 62 75 72 6E
   (The saltp is "aes128-cts-hmac-sha256-128" | 0x00 |
    random 16 byte valid UTF-8 sequence | "ATHENA.MIT.EDUraeburn")
   128-bit master key:
      3C 44 03 85 28 06 BF 5C EE E6 36 48 6C 29 2F D6

   Saltp for creating 256-bit master key:
      61 65 73 32 35 36 2D 63 74 73 2D 68 6D 61 63 2D
      73 68 61 33 38 34 2D 31 39 32 00 10 DF 9D D7 83
      E5 BC 8A CE A1 73 0E 74 35 5F 61 41 54 48 45 4E
      41 2E 4D 49 54 2E 45 44 55 72 61 65 62 75 72 6E
   (The saltp is "aes256-cts-hmac-sha384-192" | 0x00 |
    random 16 byte valid UTF-8 sequence | "ATHENA.MIT.EDUraeburn")
   256-bit master key:
      53 96 0C AF 44 D5 57 4D FF 4D 44 37 38 75 22 B0
      7F 5B 02 5C 5E 65 BF EF 29 C2 B4 28 98 3B 37 08

   Sample results for key derivation:
   ----------------------------------

   enctype aes128-cts-hmac-sha256-128:
   128-bit master key:
      37 05 D9 60 80 C1 77 28 A0 E8 00 EA B6 E0 D2 3C
   Kc value for key usage 2 (constant = 0x0000000299):
      B3 1A 01 8A 48 F5 47 76 F4 03 E9 A3 96 32 5D C3
   Ke value for key usage 2 (constant = 0x00000002AA):
      9B 19 7D D1 E8 C5 60 9D 6E 67 C3 E3 7C 62 C7 2E
   Ki value for key usage 2 (constant = 0x0000000255):
      9F DA 0E 56 AB 2D 85 E1 56 9A 68 86 96 C2 6A 6C

   enctype aes256-cts-hmac-sha384-192:
   256-bit master key:
      6D 40 4D 37 FA F7 9F 9D F0 D3 35 68 D3 20 66 98
      00 EB 48 36 47 2E A8 A0 26 D1 6B 71 82 46 0C 52
   Kc value for key usage 2 (constant = 0x0000000299):
      EF 57 18 BE 86 CC 84 96 3D 8B BB 50 31 E9 F5 C4
      BA 41 F2 8F AF 69 E7 3D



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   Ke value for key usage 2 (constant = 0x00000002AA):
      56 AB 22 BE E6 3D 82 D7 BC 52 27 F6 77 3F 8E A7
      A5 EB 1C 82 51 60 C3 83 12 98 0C 44 2E 5C 7E 49
   Ki value for key usage 2 (constant = 0x0000000255):
      69 B1 65 14 E3 CD 8E 56 B8 20 10 D5 C7 30 12 B6
      22 C4 D0 0F FC 23 ED 1F

   Sample encryptions (using the default cipher state):
   ----------------------------------------------------

   128-bit AES key:
      2B 7E 15 16 28 AE D2 A6 AB F7 15 88 09 CF 4F 3C
   128-bit HMAC key:
      67 C3 31 A4 D7 AB 52 EF 3A A9 73 E0 39 AD D3 32
   Nonce:
      7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 A3 71 48
   Plaintext: (length less than block size)
      49 6E 63 6F 6E 63 65 69 76 61 62 6C 65
   AES Output:
      1C 17 3E AD FC 67 C8 BC B3 A5 93 02 98 CB FC 60
   HMAC Output (truncated):
      35 E8 32 B2 EB F4 6A 46 C2 E6 50 D2 50 AB 84 43
   Ciphertext: (Nonce* | AES Output** | Truncated HMAC Output)
      7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 CB FC 60
      1C 17 3E AD FC 67 C8 BC B3 A5 93 02 98 35 E8 32
      B2 EB F4 6A 46 C2 E6 50 D2 50 AB 84 43

   *   Only the first 13 bytes of Nonce are sent.
   **  The AES Output is split and rearranged as described in Section 5
       since the plaintext length is less than the block size.

   128-bit AES key:
      2B 7E 15 16 28 AE D2 A6 AB F7 15 88 09 CF 4F 3C
   128-bit HMAC key:
      67 C3 31 A4 D7 AB 52 EF 3A A9 73 E0 39 AD D3 32
   Nonce:
      7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 A3 71 48
   Plaintext: (length equals block size)
      67 61 73 74 72 6F 69 6E 74 65 73 74 69 6E 61 6C
   AES Output:
      F6 71 0B 75 0C 60 65 E8 2E BF F8 9D DC E0 C9 B9
   HMAC Output (truncated):
      7B 2C D9 70 E6 DF 18 F5 E0 3D 8B 8E 40 02 F4 C0
   Ciphertext: (Nonce | AES Output | Truncated HMAC Output)
      7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 A3 71 48
      F6 71 0B 75 0C 60 65 E8 2E BF F8 9D DC E0 C9 B9
      7B 2C D9 70 E6 DF 18 F5 E0 3D 8B 8E 40 02 F4 C0




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   256-bit AES key:
      60 3D EB 10 15 CA 71 BE 2B 73 AE F0 85 7D 77 81
      1F 35 2C 07 3B 61 08 D7 2D 98 10 A3 09 14 DF F4
   192-bit HMAC key:
      37 16 14 EB 62 24 E1 F0 C4 72 6E E6 BE A7 A3 D2
      F4 62 C6 AC 66 42 A6 AC
   Nonce:
      7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 A3 71 48
   Plaintext: (length less than block size)
      49 6E 63 6F 6E 63 65 69 76 61 62 6C 65
   AES Output:
      BD AE EC 5C F9 C9 B6 3C 9D DB A2 B7 9D 5C 6C 0B
   HMAC Output (truncated):
      65 D4 C7 07 8E 14 65 8B C9 B3 C4 EA F5 F7 C2 6F
      ED 36 AC 7A CD 59 19 2B
   Ciphertext: (Nonce* | AES Output* | Truncated HMAC Output)
      7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 5C 6C 0B
      BD AE EC 5C F9 C9 B6 3C 9D DB A2 B7 9D 65 D4 C7
      07 8E 14 65 8B C9 B3 C4 EA F5 F7 C2 6F ED 36 AC
      7A CD 59 19 2B

   *   Only the first 13 bytes of Nonce are sent.
   **  The AES Output is split and rearranged as described in Section 5
       since the plaintext length is less than the block size.

   256-bit AES key:
      60 3D EB 10 15 CA 71 BE 2B 73 AE F0 85 7D 77 81
      1F 35 2C 07 3B 61 08 D7 2D 98 10 A3 09 14 DF F4
   192-bit HMAC key:
      37 16 14 EB 62 24 E1 F0 C4 72 6E E6 BE A7 A3 D2
      F4 62 C6 AC 66 42 A6 AC
   Nonce:
      7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 A3 71 48
   Plaintext: (length equals block size)
      67 61 73 74 72 6F 69 6E 74 65 73 74 69 6E 61 6C
   AES Output:
      5D E5 49 BE D6 50 23 18 78 8F 14 D2 E1 17 E0 5A
   HMAC Output (truncated):
      2C EA DF D5 B0 60 38 DE A9 22 29 2D 7C 56 50 10
      C5 D6 D2 8D F6 21 E9 7A
   Ciphertext: (Nonce | AES Output | Truncated HMAC Output)
      7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 A3 71 48
      5D E5 49 BE D6 50 23 18 78 8F 14 D2 E1 17 E0 5A
      2C EA DF D5 B0 60 38 DE A9 22 29 2D 7C 56 50 10
      C5 D6 D2 8D F6 21 E9 7A

   128-bit AES key:
      9B 19 7D D1 E8 C5 60 9D 6E 67 C3 E3 7C 62 C7 2E



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Internet-Draft      AES-CTS HMAC-SHA2 For Kerberos 5       June 28, 2013


   128-bit HMAC key:
      9F DA 0E 56 AB 2D 85 E1 56 9A 68 86 96 C2 6A 6C
   Nonce:
      8D 32 50 F6 36 AB 81 02 BE 6F AB 1E 57 D8 F8 17
   Plaintext: (length greater than the block size)
      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
      10 11 12 13 14
   AES Output:
      13 64 FB 39 DC C0 E3 D9 83 A7 DB 5B 4B 9F FB CA
      42 F6 65 88 29
   HMAC Output (truncated):
      F2 1F C8 95 75 AE 93 C7 57 18 AB 3C 7C FB 28 E1
   Ciphertext: (Nonce | AES Output | HMAC Output)
      8D 32 50 F6 36 AB 81 02 BE 6F AB 1E 57 D8 F8 17
      13 64 FB 39 DC C0 E3 D9 83 A7 DB 5B 4B 9F FB CA
      42 F6 65 88 29 F2 1F C8 95 75 AE 93 C7 57 18 AB
      3C 7C FB 28 E1

   256-bit AES key:
      56 AB 22 BE E6 3D 82 D7 BC 52 27 F6 77 3F 8E A7
      A5 EB 1C 82 51 60 C3 83 12 98 0C 44 2E 5C 7E 49
   192-bit HMAC key:
      69 B1 65 14 E3 CD 8E 56 B8 20 10 D5 C7 30 12 B6
      22 C4 D0 0F FC 23 ED 1F
   Nonce:
      8D 32 50 F6 36 AB 81 02 BE 6F AB 1E 57 D8 F8 17
   Plaintext: (length greater than the block size)
      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
      10 11 12 13 14
   AES Output:
      50 CB FF DC DF 38 69 D7 0B EA FF C3 2C 47 0B C6
      5B 72 C3 37 2D
   HMAC Output (truncated):
      6E D7 B3 47 E9 0B BD 8F 31 F5 79 58 F9 69 50 BA
      A1 41 64 6E 65 6C F6 7C
   Ciphertext: (Nonce | AES Output | HMAC Output)
      8D 32 50 F6 36 AB 81 02 BE 6F AB 1E 57 D8 F8 17
      50 CB FF DC DF 38 69 D7 0B EA FF C3 2C 47 0B C6
      5B 72 C3 37 2D 6E D7 B3 47 E9 0B BD 8F 31 F5 79
      58 F9 69 50 BA A1 41 64 6E 65 6C F6 7C

   Sample checksums:
   -----------------

   Checksum type: hmac-sha256-128-aes128
   128-bit master key:
      37 05 D9 60 80 C1 77 28 A0 E8 00 EA B6 E0 D2 3C
   128-bit HMAC key (Kc, key usage 2):



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Internet-Draft      AES-CTS HMAC-SHA2 For Kerberos 5       June 28, 2013


      B3 1A 01 8A 48 F5 47 76 F4 03 E9 A3 96 32 5D C3
   Plaintext:
      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
      10 11 12 13 14
   Checksum:
      D7 83 67 18 66 43 D6 7B 41 1C BA 91 39 FC 1D EE

   Checksum type: hmac-sha384-192-aes256
   256-bit master key:
      6D 40 4D 37 FA F7 9F 9D F0 D3 35 68 D3 20 66 98
      00 EB 48 36 47 2E A8 A0 26 D1 6B 71 82 46 0C 52
   192-bit HMAC key (Kc, key usage 2):
      EF 57 18 BE 86 CC 84 96 3D 8B BB 50 31 E9 F5 C4
      BA 41 F2 8F AF 69 E7 3D
   Plaintext:
      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
      10 11 12 13 14
   Checksum:
      45 EE 79 15 67 EE FC A3 7F 4A C1 E0 22 2D E8 0D
      43 C3 BF A0 66 99 67 2A

Authors' Addresses

   Kelley W. Burgin
   National Security Agency

   EMail: kwburgi@tycho.ncsc.mil

   Michael A. Peck
   The MITRE Corporation

   EMail: mpeck@mitre.org



















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