Request for Comments: 8009
Category: Informational
ISSN: 20701721
National Security Agency
M. Peck
The MITRE Corporation
K. Burgin
October 2016
AES Encryption with HMACSHA2 for Kerberos 5
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 document is not an Internet Standards Track specification; it is published for informational purposes.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfceditor.org/info/rfc8009.
Copyright Notice

Copyright © 2016 IETF Trust and the persons identified as the document authors. All rights reserved.
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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Protocol Key Representation . . . . . . . . . . . . . . . . . 3 3. Key Derivation Function . . . . . . . . . . . . . . . . . . . 3 4. Key Generation from Pass Phrases . . . . . . . . . . . . . . . 4 5. Kerberos Algorithm Protocol Parameters . . . . . . . . . . . . 5 6. Checksum Parameters . . . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 8.1. Random Values in Salt Strings . . . . . . . . . . . . . . 9 8.2. Algorithm Rationale . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1. Normative References . . . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . . 11 Appendix A. Test Vectors . . . . . . . . . . . . . . . . . . . . 12 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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 Message Authentication Codes (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 SHA384 (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 (PRF) used by PBKDF2 is HMACSHA256 or HMACSHA384. (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 cipher state 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)
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 aes256ctshmacsha384192, k must be no greater than 384 bits.
The ktruncate function is defined in Section 5.1 of [RFC3961]. 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)
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 4 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 cipher state defined in RFC 3961 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 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 aes128ctshmacsha256128 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 4 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)
cipher state: a 128bit CBC initialization vector derived from a previous ciphertext (if any) 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)

where "prf" is the octetstring 0x707266

6. Checksum Parameters

The following parameters apply to the checksum types hmacsha256128aes128 and hmacsha384192aes256, which are the associated checksums for aes128ctshmacsha256128 and aes256ctshmacsha384192, respectively. associated cryptosystem: aes128ctshmacsha256128 or aes256ctshmacsha384192 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 has assigned encryption type numbers as follows in the "Kerberos Encryption Type Numbers" registry.
etype encryption type Reference    19 aes128ctshmacsha256128 RFC 8009 20 aes256ctshmacsha384192 RFC 8009
IANA has assigned checksum type numbers as follows in the "Kerberos Checksum Type Numbers" registry.
sumtype Checksum type checksum Reference value size     19 hmacsha256128aes128 16 RFC 8009 20 hmacsha384192aes256 24 RFC 8009
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 guidance on random number generation.
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 passwordguess attempts. Nonetheless, computing power continues to rapidly improve, including the potential for use of graphics processing units (GPUs) in passwordguess 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

The 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 UTF8compatible 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:
* Keys for crossrealm krbtgt services [RFC4120] are typically managed by entering the same password at two Key Distribution Centers (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 checking of password history.
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 enctype name "aes256ctshmacsha384192", the truncation of the HMACSHA384 output to 192 bits results in an overall 192bit level of security.
9. References
9.1. Normative References

[FIPS180] National Institute of Standards and Technology, "Secure Hash Standard", FIPS PUB 1804, DOI 10.6028/NIST.FIPS.1804, August 2015. [FIPS197] National Institute of Standards and Technology, "Advanced Encryption Standard (AES)", FIPS PUB 197, November 2001. [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed Hashing for Message Authentication", RFC 2104, DOI 10.17487/RFC2104, February 1997, <http://www.rfceditor.org/info/rfc2104>. [RFC2898] Kaliski, B., "PKCS #5: PasswordBased Cryptography Specification Version 2.0", RFC 2898, DOI 10.17487/RFC2898, September 2000, <http://www.rfceditor.org/info/rfc2898>. [RFC3629] Yergeau, F., "UTF8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, <http://www.rfceditor.org/info/rfc3629>. [RFC3961] Raeburn, K., "Encryption and Checksum Specifications for Kerberos 5", RFC 3961, DOI 10.17487/RFC3961, February 2005, <http://www.rfceditor.org/info/rfc3961>. [RFC3962] Raeburn, K., "Advanced Encryption Standard (AES) Encryption for Kerberos 5", RFC 3962, DOI 10.17487/RFC3962, February 2005, <http://www.rfceditor.org/info/rfc3962>. [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.
9.2. Informative References

[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, June 2005, <http://www.rfceditor.org/info/rfc4086>. [RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The Kerberos Network Authentication Service (V5)", RFC 4120, DOI 10.17487/RFC4120, July 2005, <http://www.rfceditor.org/info/rfc4120>. [RFC4556] Zhu, L. and B. Tung, "Public Key Cryptography for Initial Authentication in Kerberos (PKINIT)", RFC 4556, DOI 10.17487/RFC4556, June 2006, <http://www.rfceditor.org/info/rfc4556>. [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 800132, 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 16byte 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 16byte 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 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: 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 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 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: 
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 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
Acknowledgements

Kelley Burgin was employed at the National Security Agency during much of the work on this document.
Authors' Addresses

Michael J. Jenkins
National Security AgencyEmail: mjjenki@tycho.ncsc.mil
Michael A. Peck
The MITRE CorporationEmail:
mpeck@mitre.org Kelley W. Burgin Email: kelley.burgin@gmail.com