AES Encryption with HMACSHA2 for Kerberos 5
draftietfkittenaesctshmacsha211
The information below is for an old version of the document that is already published as an RFC.
Document  Type 
This is an older version of an InternetDraft that was ultimately published as RFC 8009.



Authors  Michael J. Jenkins , Michael Peck , Kelley W. Burgin  
Last updated  20161027 (Latest revision 20160826)  
Replaces  draftietfkittenaescbchmacsha2  
RFC stream  Internet Engineering Task Force (IETF)  
Formats  
Reviews 
GENART Telechat review
(of
10)
Ready with Issues
SECDIR Last Call review
(of
10)
Has Issues


Additional resources  Mailing list discussion  
Stream  WG state  Submitted to IESG for Publication  
Document shepherd  Benjamin Kaduk  
Shepherd writeup  Show Last changed 20160705  
IESG  IESG state  RFC 8009 (Informational)  
Consensus boilerplate  Yes  
Telechat date  (None)  
Responsible AD  Stephen Farrell  
Send notices to  "Benjamin Kaduk" <kaduk@mit.edu>  
IANA  IANA review state  Version Changed  Review Needed  
IANA action state  RFCEdAck  
RFC Editor  RFC Editor state  AUTH48DONE  
Details 
draftietfkittenaesctshmacsha211
Network Working Group M. Jenkins Internet Draft National Security Agency Intended Status: Informational M. Peck Expires: February 27, 2017 The MITRE Corporation K. Burgin August 26, 2016 AES Encryption with HMACSHA2 for Kerberos 5 draftietfkittenaesctshmacsha211 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 SHA2 hash for integrity. Status of this Memo This InternetDraft is submitted in full conformance with the provisions of BCP 78 and BCP 79. InternetDrafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as InternetDrafts. The list of current Internet Drafts is at http://datatracker.ietf.org/drafts/current/. InternetDrafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use InternetDrafts as reference material or to cite them other than as "work in progress." This InternetDraft will expire on February 27, 2017. Copyright and License Notice Copyright (c) 2016 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 Provisions Relating to IETF Documents (http://trustee.ietf.org/licenseinfo) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Jenkins, et al. Expires February 27, 2017 [Page 1] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Protocol Key Representation . . . . . . . . . . . . . . . . . 3 3. Key Derivation Function . . . . . . . . . . . . . . . . . . . 3 4. Key Generation from Pass Phrases . . . . . . . . . . . . . . . 5 5. Kerberos Algorithm Protocol Parameters . . . . . . . . . . . . 5 6. Checksum Parameters . . . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 8.1. Random Values in Salt Strings . . . . . . . . . . . . . . 9 8.2. Algorithm Rationale . . . . . . . . . . . . . . . . . . . 9 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 10.1. Normative References . . . . . . . . . . . . . . . . . . 10 10.2. Informative References . . . . . . . . . . . . . . . . . 10 Appendix A. Test Vectors . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Jenkins, et al. Expires February 27, 2017 [Page 2] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 1. Introduction This document defines two encryption types and two corresponding checksum types for Kerberos 5 using AES with 128bit or 256bit keys. To avoid ciphertext expansion, we use a variation of the CBCCS3 mode defined in [SP80038A+], also referred to as ciphertext stealing or CTS mode. The new types conform to the framework specified in [RFC3961], but do not use the simplified profile, as the simplified profile is not compliant with modern cryptographic best practices such as calculating MACs over ciphertext rather than plaintext. The encryption and checksum types defined in this document are intended to support environments that desire to use SHA256 or SHA 384 (defined in [FIPS180]) as the hash algorithm. Differences between the encryption and checksum types defined in this document and the preexisting Kerberos AES encryption and checksum types specified in [RFC3962] are: * The pseudorandom function used by PBKDF2 is HMACSHA256 or HMAC SHA384 (HMAC is defined in [RFC2104]). * A key derivation function from [SP800108] using the SHA256 or SHA384 hash algorithm is used to produce keys for encryption, integrity protection, and checksum operations. * The HMAC is calculated over the cipherstate concatenated with the AES output, instead of being calculated over the confounder and plaintext. This allows the message receiver to verify the integrity of the message before decrypting the message. * The HMAC algorithm uses the SHA256 or SHA384 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 Derivation Function We use a key derivation function from Section 5.1 of [SP800108] which uses the HMAC algorithm as the PRF. function KDFHMACSHA2(key, label, [context,] k): ktruncate(K1) Jenkins, et al. Expires February 27, 2017 [Page 3] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 where the value of K1 is computed as below. key: The source of entropy from which subsequent keys are derived (this is known as Ki in [SP800108]). label: An octet string describing the intended usage of the derived key. context: This parameter is optional. An octet string containing the information related to the derived keying material. This specification does not dictate a specific format for the context field. The context field is only used by the pseudorandom function defined in section 5, where it is set to the pseudorandom function's octetstring input parameter. The content of the octetstring input parameter is defined by the application that uses it. k: Length in bits of the key to be outputted, expressed in bigendian binary representation in 4 bytes (this is called L in [SP800108]). Specifically, k=128 is represented as 0x00000080, 192 as 0x000000C0, 256 as 0x00000100, and 384 as 0x00000180. When the encryption type is aes128ctshmacsha256128, k must be no greater than 256 bits. When the encryption type is aes256ctshmac sha384192, k must be no greater than 384 bits. The ktruncate function is defined in [RFC3961], Section 5.1. It returns the 'k' leftmost bits of the bitstring input. In all computations in this document,  indicates concatenation. When the encryption type is aes128ctshmacsha256128, then K1 is computed as follows: If the context parameter is not present: K1 = HMACSHA256(key, 0x00000001  label  0x00  k) If the context parameter is present: K1 = HMACSHA256(key, 0x00000001  label  0x00  context  k) When the encryption type is aes256ctshmacsha384192, then K1 is computed as follows: If the context parameter is not present: K1 = HMACSHA384(key, 0x00000001  label  0x00  k) If the context parameter is present: K1 = HMACSHA384(key, 0x00000001  label  0x00  context  k) Jenkins, et al. Expires February 27, 2017 [Page 4] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 In the definitions of K1 above, '0x00000001' is the i parameter (the iteration counter) from Section 5.1 of [SP800108]. 4. Key Generation from Pass Phrases As defined below, the stringtokey function uses PBKDF2 [RFC2898] and KDFHMACSHA2 to derive the basekey from a passphrase and salt. The stringtokey parameter string is four octets indicating an unsigned number in bigendian order, consistent with [RFC3962], except that the default is decimal 32768 if the parameter is not specified. To ensure that different longterm basekeys are used with different enctypes, we prepend the enctype name to the salt, separated by a null byte. The enctypename is "aes128ctshmacsha256128" or "aes256ctshmacsha384192" (without the quotes). The user's longterm basekey is derived as follows: iter_count = stringtokey parameter, default is decimal 32768 saltp = enctypename  0x00  salt tkey = randomtokey(PBKDF2(passphrase, saltp, iter_count, keylength)) basekey = randomtokey(KDFHMACSHA2(tkey, "kerberos", keylength)) where "kerberos" is the octetstring 0x6B65726265726F73. where PBKDF2 is the function of that name from RFC 2898, the pseudorandom function used by PBKDF2 is HMACSHA256 when the enctype is "aes128ctshmacsha256128" and HMACSHA384 when the enctype is "aes256ctshmacsha384192", the value for keylength is the AES key length (128 or 256 bits), and the algorithm KDFHMACSHA2 is defined in Section 3. 5. Kerberos Algorithm Protocol Parameters The RFC 3961 cipher state that maintains cryptographic state across different encryption operations using the same key is used as the formal initialization vector (IV) input into CBCCS3. The plaintext is prepended with a 16octet random value generated by the message originator, known as a confounder. The ciphertext is a concatenation of the output of AES in CBCCS3 mode and the HMAC of the cipher state concatenated with the AES output. The HMAC is computed using either SHA256 or SHA384 depending on the encryption type. The output of HMACSHA256 is truncated to 128 bits and the output of HMACSHA384 is truncated to Jenkins, et al. Expires February 27, 2017 [Page 5] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 192 bits. Sample test vectors are given in Appendix A. Decryption is performed by removing the HMAC, verifying the HMAC against the cipher state concatenated with the ciphertext, and then decrypting the ciphertext if the HMAC is correct. Finally, the first 16 octets of the decryption output (the confounder) is discarded, and the remainder is returned as the plaintext decryption output. The following parameters apply to the encryption types aes128cts hmacsha256128 and aes256ctshmacsha384192. protocol key format: as defined in Section 2. specific key structure: three derived keys: { Kc, Ke, Ki }. Kc: the checksum key, inputted into HMAC to provide the checksum mechanism defined in Section 6. Ke: the encryption key, inputted into AES encryption and decryption as defined in "encryption function" and "decryption function" below. Ki: the integrity key, inputted into HMAC to provide authenticated encryption as defined in "encryption function" and "decryption function" below. required checksum mechanism: as defined in Section 6. keygeneration seed length: key size (128 or 256 bits). stringtokey function: as defined in Section 4. default stringtokey parameters: iteration count of decimal 32768. randomtokey function: identity function. keyderivation function: KDFHMACSHA2 as defined in Section 3. The key usage number is expressed as four octets in bigendian order. If the enctype is aes128ctshmacsha256128: Kc = KDFHMACSHA2(basekey, usage  0x99, 128) Ke = KDFHMACSHA2(basekey, usage  0xAA, 128) Ki = KDFHMACSHA2(basekey, usage  0x55, 128) If the enctype is aes256ctshmacsha384192: Kc = KDFHMACSHA2(basekey, usage  0x99, 192) Ke = KDFHMACSHA2(basekey, usage  0xAA, 256) Ki = KDFHMACSHA2(basekey, usage  0x55, 192) Jenkins, et al. Expires February 27, 2017 [Page 6] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 cipher state: a 128bit CBC initialization vector derived from a previous (if any) ciphertext using the same encryption key, as specified below. initial cipher state: all bits zero. encryption function: as follows, where E() is AES encryption in CBCCS3 mode, and h is the size of truncated HMAC (128 bits or 192 bits as described above). N = random value of length 128 bits (the AES block size) IV = cipher state C = E(Ke, N  plaintext, IV) H = HMAC(Ki, IV  C) ciphertext = C  H[1..h] Steps to compute the 128bit cipher state: L = length of C in bits portion C into 128bit blocks, placing any remainder of less than 128 bits into a final block if L == 128: cipher state = C else if L mod 128 > 0: cipher state = last full (128bit) block of C (the nexttolast block) else if L mod 128 == 0: cipher state = nexttolast block of C (note that L will never be less than 128 because of the presence of N in the encryption input) decryption function: as follows, where D() is AES decryption in CBCCS3 mode, and h is the size of truncated HMAC. (C, H) = ciphertext (Note: H is the last h bits of the ciphertext) IV = cipher state if H != HMAC(Ki, IV  C)[1..h] stop, report error (N, P) = D(Ke, C, IV) Note: N is set to the first block of the decryption output, P is set to the rest of the output. cipher state = same as described above in encryption function pseudorandom function: If the enctype is aes128ctshmacsha256128: PRF = KDFHMACSHA2(inputkey, "prf", octetstring, 256) If the enctype is aes256ctshmacsha384192: PRF = KDFHMACSHA2(inputkey, "prf", octetstring, 384) Jenkins, et al. Expires February 27, 2017 [Page 7] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 where "prf" is the octetstring 0x707266 6. Checksum Parameters The following parameters apply to the checksum types hmacsha256128 aes128 and hmacsha384192aes256, which are the associated checksums for aes128ctshmacsha256128 and aes256ctshmacsha384192, respectively. associated cryptosystem: aes128ctshmacsha256128 or aes256cts hmacsha384192 as appropriate. get_mic: HMAC(Kc, message)[1..h]. where h is 128 bits for checksum type hmacsha256128aes128 and 192 bits for checksum type hmacsha384192aes256 verify_mic: get_mic and compare. 7. IANA Considerations IANA is requested to assign: Encryption type numbers for aes128ctshmacsha256128 and aes256ctshmacsha384192 in the Kerberos Encryption Type Numbers registry. Etype Encryption type Reference    TBD1 aes128ctshmacsha256128 [this document] TBD2 aes256ctshmacsha384192 [this document] Checksum type numbers for hmacsha256128aes128 and hmacsha384192 aes256 in the Kerberos Checksum Type Numbers registry. Sumtype Checksum type Size Reference     TBD3 hmacsha256128aes128 16 [this document] TBD4 hmacsha384192aes256 24 [this document] 8. Security Considerations This specification requires implementations to generate random values. The use of inadequate pseudorandom number generators (PRNGs) can result in little or no security. The generation of quality random numbers is difficult. [RFC4086] offers random number Jenkins, et al. Expires February 27, 2017 [Page 8] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 generation guidance. This document specifies a mechanism for generating keys from passphrases or passwords. The use of PBKDF2, a salt, and a large iteration count adds some resistance to offline dictionary attacks by passive eavesdroppers. Salting prevents rainbow table attacks, while large iteration counts slow password guess attempts. Nonetheless, computing power continues to rapidly improve, including the potential for use of graphics processing units (GPUs) in password guess attempts. It is important to choose strong passphrases. Use of Kerberos extensions that protect against offline dictionary attacks should also be considered, as should the use of public key cryptography for initial Kerberos authentication [RFC4556] to eliminate the use of passwords or passphrases within the Kerberos protocol. The NIST guidance in section 5.3 of [SP80038A], requiring that CBC initialization vectors be unpredictable, is satisfied by the use of a random confounder as the first block of plaintext. The confounder fills the cryptographic role typically played by an initialization vector. This approach was chosen to align with other Kerberos cryptosystem approaches. 8.1. Random Values in Salt Strings NIST guidance in Section 5.1 of [SP800132] requires at least 128 bits of the salt to be randomly generated. The stringtokey function as defined in [RFC3961] requires the salt to be valid UTF8 strings [RFC3629]. Not every 128bit random string will be valid UTF8, so a UTF8 compatible encoding would be needed to encapsulate the random bits. However, using a salt containing a random portion may have the following issues with some implementations: * Crossrealm krbtgt keys are typically 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. * Random salts may interfere with password history checking. 8.2. Algorithm Rationale This document has been written to be consistent with common implementations of AES and SHA2. The encryption and hash algorithm sizes have been chosen to create a consistent level of protection, with consideration to implementation efficiencies. So, for instance, SHA384, which would normally be matched to AES192, is instead matched to AES256 to leverage the fact that there are efficient hardware implementations of AES256. Note that, as indicated by the Jenkins, et al. Expires February 27, 2017 [Page 9] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 enctype name "aes256ctshmacsha384192", the truncation of the HMACSHA384 output to 192bits results in an overall 192bit level of security. 9. Acknowledgements Kelley Burgin was employed at the National Security Agency during much of the work on this document. 10. References 10.1. Normative References [RFC2104] Krawczyk, H. et al., "HMAC: KeyedHashing for Message Authentication", RFC 2104, February 1997. [RFC2898] Kaliski, B., "PKCS #5: PasswordBased Cryptography Specification Version 2.0", RFC 2898, September 2000. [RFC3629] Yergeau, F., "UTF8, a transformation format of ISO 10646", RFC 3629, November 2003. [RFC3961] Raeburn, K., "Encryption and Checksum Specifications for Kerberos 5", RFC 3961, February 2005. [RFC3962] Raeburn, K., "Advanced Encryption Standard (AES) Encryption for Kerberos 5", RFC 3962, February 2005. [FIPS180] National Institute of Standards and Technology, "Secure Hash Standard", FIPS PUB 1804, August 2015. [FIPS197] National Institute of Standards and Technology, "Advanced Encryption Standard (AES)", FIPS PUB 197, November 2001. [SP80038A+] National Institute of Standards and Technology, "Recommendation for Block Cipher Modes of Operation: Three Variants of Ciphertext Stealing for CBC Mode", NIST Special Publication 80038A Addendum, October 2010. [SP800108] National Institute of Standards and Technology, "Recommendation for Key Derivation Using Pseudorandom Functions", NIST Special Publication 800108, October 2009. 10.2. Informative References [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, Jenkins, et al. Expires February 27, 2017 [Page 10] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005. [SP80038A] National Institute of Standards and Technology, "Recommendation for Block Cipher Modes of Operation: Methods and Techniques", NIST Special Publication 80038A, December 2001. [SP800132] National Institute of Standards and Technology, "Recommendation for PasswordBased Key Derivation, Part 1: Storage Applications", NIST Special Publication 800 132, June 2010. Appendix A. Test Vectors Sample results for stringtokey conversion:  Iteration count = 32768 Pass phrase = "password" Saltp for creating 128bit basekey: 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 "aes128ctshmacsha256128"  0x00  random 16 byte valid UTF8 sequence  "ATHENA.MIT.EDUraeburn") 128bit basekey: 08 9B CA 48 B1 05 EA 6E A7 7C A5 D2 F3 9D C5 E7 Saltp for creating 256bit basekey: 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 "aes256ctshmacsha384192"  0x00  random 16 byte valid UTF8 sequence  "ATHENA.MIT.EDUraeburn") 256bit basekey: 45 BD 80 6D BF 6A 83 3A 9C FF C1 C9 45 89 A2 22 36 7A 79 BC 21 C4 13 71 89 06 E9 F5 78 A7 84 67 Sample results for key derivation:  enctype aes128ctshmacsha256128: 128bit basekey: 37 05 D9 60 80 C1 77 28 A0 E8 00 EA B6 E0 D2 3C Jenkins, et al. Expires February 27, 2017 [Page 11] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 Kc value for key usage 2 (label = 0x0000000299): B3 1A 01 8A 48 F5 47 76 F4 03 E9 A3 96 32 5D C3 Ke value for key usage 2 (label = 0x00000002AA): 9B 19 7D D1 E8 C5 60 9D 6E 67 C3 E3 7C 62 C7 2E Ki value for key usage 2 (label = 0x0000000255): 9F DA 0E 56 AB 2D 85 E1 56 9A 68 86 96 C2 6A 6C enctype aes256ctshmacsha384192: 256bit basekey: 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 (label = 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 Ke value for key usage 2 (label = 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 (label = 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 (all using the default cipher state):  These sample encryptions use the above sample key derivation results, including use of the same basekey and key usage values. The following test vectors are for enctype aes128ctshmacsha256128: Plaintext: (empty) Confounder: 7E 58 95 EA F2 67 24 35 BA D8 17 F5 45 A3 71 48 128bit AES key (Ke): 9B 19 7D D1 E8 C5 60 9D 6E 67 C3 E3 7C 62 C7 2E 128bit HMAC key (Ki): 9F DA 0E 56 AB 2D 85 E1 56 9A 68 86 96 C2 6A 6C AES Output: EF 85 FB 89 0B B8 47 2F 4D AB 20 39 4D CA 78 1D Truncated HMAC Output: AD 87 7E DA 39 D5 0C 87 0C 0D 5A 0A 8E 48 C7 18 Ciphertext (AES Output  HMAC Output): EF 85 FB 89 0B B8 47 2F 4D AB 20 39 4D CA 78 1D AD 87 7E DA 39 D5 0C 87 0C 0D 5A 0A 8E 48 C7 18 Plaintext: (length less than block size) 00 01 02 03 04 05 Confounder: Jenkins, et al. Expires February 27, 2017 [Page 12] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 7B CA 28 5E 2F D4 13 0F B5 5B 1A 5C 83 BC 5B 24 128bit AES key (Ke): 9B 19 7D D1 E8 C5 60 9D 6E 67 C3 E3 7C 62 C7 2E 128bit HMAC key (Ki): 9F DA 0E 56 AB 2D 85 E1 56 9A 68 86 96 C2 6A 6C AES Output: 84 D7 F3 07 54 ED 98 7B AB 0B F3 50 6B EB 09 CF B5 54 02 CE F7 E6 Truncated HMAC Output: 87 7C E9 9E 24 7E 52 D1 6E D4 42 1D FD F8 97 6C Ciphertext: 84 D7 F3 07 54 ED 98 7B AB 0B F3 50 6B EB 09 CF B5 54 02 CE F7 E6 87 7C E9 9E 24 7E 52 D1 6E D4 42 1D FD F8 97 6C Plaintext: (length equals block size) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F Confounder: 56 AB 21 71 3F F6 2C 0A 14 57 20 0F 6F A9 94 8F 128bit AES key (Ke): 9B 19 7D D1 E8 C5 60 9D 6E 67 C3 E3 7C 62 C7 2E 128bit HMAC key (Ki): 9F DA 0E 56 AB 2D 85 E1 56 9A 68 86 96 C2 6A 6C AES Output: 35 17 D6 40 F5 0D DC 8A D3 62 87 22 B3 56 9D 2A E0 74 93 FA 82 63 25 40 80 EA 65 C1 00 8E 8F C2 Truncated HMAC Output: 95 FB 48 52 E7 D8 3E 1E 7C 48 C3 7E EB E6 B0 D3 Ciphertext: 35 17 D6 40 F5 0D DC 8A D3 62 87 22 B3 56 9D 2A E0 74 93 FA 82 63 25 40 80 EA 65 C1 00 8E 8F C2 95 FB 48 52 E7 D8 3E 1E 7C 48 C3 7E EB E6 B0 D3 Plaintext: (length greater than block size) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 Confounder: A7 A4 E2 9A 47 28 CE 10 66 4F B6 4E 49 AD 3F AC 128bit AES key (Ke): 9B 19 7D D1 E8 C5 60 9D 6E 67 C3 E3 7C 62 C7 2E 128bit HMAC key (Ki): 9F DA 0E 56 AB 2D 85 E1 56 9A 68 86 96 C2 6A 6C AES Output: 72 0F 73 B1 8D 98 59 CD 6C CB 43 46 11 5C D3 36 C7 0F 58 ED C0 C4 43 7C 55 73 54 4C 31 C8 13 BC E1 E6 D0 72 C1 Truncated HMAC Output: 86 B3 9A 41 3C 2F 92 CA 9B 83 34 A2 87 FF CB FC Jenkins, et al. Expires February 27, 2017 [Page 13] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 Ciphertext: 72 0F 73 B1 8D 98 59 CD 6C CB 43 46 11 5C D3 36 C7 0F 58 ED C0 C4 43 7C 55 73 54 4C 31 C8 13 BC E1 E6 D0 72 C1 86 B3 9A 41 3C 2F 92 CA 9B 83 34 A2 87 FF CB FC The following test vectors are for enctype aes256ctshmacsha384192: Plaintext: (empty) Confounder: F7 64 E9 FA 15 C2 76 47 8B 2C 7D 0C 4E 5F 58 E4 256bit AES key (Ke): 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 192bit HMAC key (Ki): 69 B1 65 14 E3 CD 8E 56 B8 20 10 D5 C7 30 12 B6 22 C4 D0 0F FC 23 ED 1F AES Output: 41 F5 3F A5 BF E7 02 6D 91 FA F9 BE 95 91 95 A0 Truncated HMAC Output: 58 70 72 73 A9 6A 40 F0 A0 19 60 62 1A C6 12 74 8B 9B BF BE 7E B4 CE 3C Ciphertext: 41 F5 3F A5 BF E7 02 6D 91 FA F9 BE 95 91 95 A0 58 70 72 73 A9 6A 40 F0 A0 19 60 62 1A C6 12 74 8B 9B BF BE 7E B4 CE 3C Plaintext: (length less than block size) 00 01 02 03 04 05 Confounder: B8 0D 32 51 C1 F6 47 14 94 25 6F FE 71 2D 0B 9A 256bit AES key (Ke): 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 192bit HMAC key (Ki): 69 B1 65 14 E3 CD 8E 56 B8 20 10 D5 C7 30 12 B6 22 C4 D0 0F FC 23 ED 1F AES Output: 4E D7 B3 7C 2B CA C8 F7 4F 23 C1 CF 07 E6 2B C7 B7 5F B3 F6 37 B9 Truncated HMAC Output: F5 59 C7 F6 64 F6 9E AB 7B 60 92 23 75 26 EA 0D 1F 61 CB 20 D6 9D 10 F2 Ciphertext: 4E D7 B3 7C 2B CA C8 F7 4F 23 C1 CF 07 E6 2B C7 B7 5F B3 F6 37 B9 F5 59 C7 F6 64 F6 9E AB 7B 60 92 23 75 26 EA 0D 1F 61 CB 20 D6 9D 10 F2 Jenkins, et al. Expires February 27, 2017 [Page 14] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 Plaintext: (length equals block size) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F Confounder: 53 BF 8A 0D 10 52 65 D4 E2 76 42 86 24 CE 5E 63 256bit AES key (Ke): 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 192bit HMAC key (Ki): 69 B1 65 14 E3 CD 8E 56 B8 20 10 D5 C7 30 12 B6 22 C4 D0 0F FC 23 ED 1F AES Output: BC 47 FF EC 79 98 EB 91 E8 11 5C F8 D1 9D AC 4B BB E2 E1 63 E8 7D D3 7F 49 BE CA 92 02 77 64 F6 Truncated HMAC Output: 8C F5 1F 14 D7 98 C2 27 3F 35 DF 57 4D 1F 93 2E 40 C4 FF 25 5B 36 A2 66 Ciphertext: BC 47 FF EC 79 98 EB 91 E8 11 5C F8 D1 9D AC 4B BB E2 E1 63 E8 7D D3 7F 49 BE CA 92 02 77 64 F6 8C F5 1F 14 D7 98 C2 27 3F 35 DF 57 4D 1F 93 2E 40 C4 FF 25 5B 36 A2 66 Plaintext: (length greater than block size) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 Confounder: 76 3E 65 36 7E 86 4F 02 F5 51 53 C7 E3 B5 8A F1 256bit AES key (Ke): 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 192bit HMAC key (Ki): 69 B1 65 14 E3 CD 8E 56 B8 20 10 D5 C7 30 12 B6 22 C4 D0 0F FC 23 ED 1F AES Output: 40 01 3E 2D F5 8E 87 51 95 7D 28 78 BC D2 D6 FE 10 1C CF D5 56 CB 1E AE 79 DB 3C 3E E8 64 29 F2 B2 A6 02 AC 86 Truncated HMAC Output: FE F6 EC B6 47 D6 29 5F AE 07 7A 1F EB 51 75 08 D2 C1 6B 41 92 E0 1F 62 Ciphertext: 40 01 3E 2D F5 8E 87 51 95 7D 28 78 BC D2 D6 FE 10 1C CF D5 56 CB 1E AE 79 DB 3C 3E E8 64 29 F2 B2 A6 02 AC 86 FE F6 EC B6 47 D6 29 5F AE 07 7A 1F EB 51 75 08 D2 C1 6B 41 92 E0 1F 62 Sample checksums:  Jenkins, et al. Expires February 27, 2017 [Page 15] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 These sample checksums use the above sample key derivation results, including use of the same basekey and key usage values. Checksum type: hmacsha256128aes128 128bit HMAC key (Kc): 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: hmacsha384192aes256 192bit HMAC key (Kc): 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 Jenkins, et al. Expires February 27, 2017 [Page 16] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 Sample pseudorandom function (PRF) invocations:  PRF input octetstring: "test" (0x74657374) enctype aes128ctshmacsha256128: inputkey value / HMACSHA256 key: 37 05 D9 60 80 C1 77 28 A0 E8 00 EA B6 E0 D2 3C HMACSHA256 input message: 00 00 00 01 70 72 66 00 74 65 73 74 00 00 01 00 PRF output: 9D 18 86 16 F6 38 52 FE 86 91 5B B8 40 B4 A8 86 FF 3E 6B B0 F8 19 B4 9B 89 33 93 D3 93 85 42 95 enctype aes256ctshmacsha384192: inputkey value / HMACSHA384 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 HMACSHA384 input message: 00 00 00 01 70 72 66 00 74 65 73 74 00 00 01 80 PRF output: 98 01 F6 9A 36 8C 2B F6 75 E5 95 21 E1 77 D9 A0 7F 67 EF E1 CF DE 8D 3C 8D 6F 6A 02 56 E3 B1 7D B3 C1 B6 2A D1 B8 55 33 60 D1 73 67 EB 15 14 D2 Jenkins, et al. Expires February 27, 2017 [Page 17] InternetDraft AESCTS HMACSHA2 For Kerberos 5 August 26, 2016 Authors' Addresses Michael J. Jenkins National Security Agency EMail: mjjenki@tycho.ncsc.mil Michael A. Peck The MITRE Corporation EMail: mpeck@mitre.org Kelley W. Burgin Email: kelley.burgin@gmail.com Jenkins, et al. Expires February 27, 2017 [Page 18]