R. Poovendran
University of Washington
J. Lee
Samsung Electronics
T. Iwata
Nagoya University
June 2006
The AESCMAC 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 © The Internet Society (2006).
Abstract

The National Institute of Standards and Technology (NIST) has recently specified the Cipherbased Message Authentication Code (CMAC), which is equivalent to the OneKey CBC MAC1 (OMAC1) submitted by Iwata and Kurosawa. This memo specifies an authentication algorithm based on CMAC with the 128bit Advanced Encryption Standard (AES). This new authentication algorithm is named AESCMAC. The purpose of this document is to make the AESCMAC algorithm conveniently available to the Internet Community.
Table of Contents

1. Introduction ....................................................2 2. Specification of AESCMAC .......................................3 2.1. Basic Definitions ..........................................3 2.2. Overview ...................................................4 2.3. Subkey Generation Algorithm ................................5 2.4. MAC Generation Algorithm ...................................7 2.5. MAC Verification Algorithm .................................9 3. Security Considerations ........................................10 4. Test Vectors ...................................................11 5. Acknowledgement ................................................12 6. References .....................................................12 6.1. Normative References ......................................12 6.2. Informative References ....................................12 Appendix A. Test Code .............................................14
1. Introduction

The National Institute of Standards and Technology (NIST) has recently specified the Cipherbased Message Authentication Code (CMAC). CMAC [NISTCMAC] is a keyed hash function that is based on a symmetric key block cipher, such as the Advanced Encryption Standard [NISTAES]. CMAC is equivalent to the OneKey CBC MAC1 (OMAC1) submitted by Iwata and Kurosawa [OMAC1a, OMAC1b]. OMAC1 is an improvement of the eXtended Cipher Block Chaining mode (XCBC) submitted by Black and Rogaway [XCBCa, XCBCb], which itself is an improvement of the basic Cipher Block ChainingMessage Authentication Code (CBCMAC). XCBC efficiently addresses the security deficiencies of CBCMAC, and OMAC1 efficiently reduces the key size of XCBC.
AESCMAC provides stronger assurance of data integrity than a checksum or an errordetecting code. The verification of a checksum or an errordetecting code detects only accidental modifications of the data, while CMAC is designed to detect intentional, unauthorized modifications of the data, as well as accidental modifications.
AESCMAC achieves a security goal similar to that of HMAC [RFCHMAC]. Since AESCMAC is based on a symmetric key block cipher, AES, and HMAC is based on a hash function, such as SHA1, AESCMAC is appropriate for information systems in which AES is more readily available than a hash function.
This memo specifies the authentication algorithm based on CMAC with AES128. This new authentication algorithm is named AESCMAC.
2. Specification of AESCMAC
2.1. Basic Definitions

The following table describes the basic definitions necessary to explain the specification of AESCMAC.
x  y Concatenation. x  y is the string x concatenated with the string y. 0000  1111 is 00001111. x XOR y ExclusiveOR operation. For two equal length strings, x and y, x XOR y is their bitwise exclusiveOR. ceil(x) Ceiling function. The smallest integer no smaller than x. ceil(3.5) is 4. ceil(5) is 5. x << 1 Leftshift of the string x by 1 bit. The most significant bit disappears, and a zero comes into the least significant bit. 10010001 << 1 is 00100010. 0^n The string that consists of n zerobits. 0^3 means 000 in binary format. 10^4 means 10000 in binary format. 10^i means 1 followed by itimes repeated zeros. MSB(x) The mostsignificant bit of the string x. MSB(10010000) means 1. padding(x) 10^i padded output of input x. It is described in detail in section 2.4. Key 128bit (16octet) long key for AES128. Denoted by K. First subkey 128bit (16octet) long first subkey, derived through the subkey generation algorithm from the key K. Denoted by K1. Second subkey 128bit (16octet) long second subkey, derived through the subkey generation algorithm from the key K. Denoted by K2. Message A message to be authenticated. Denoted by M. The message can be null, which means that the length of M is 0. Message length The length of the message M in octets. Denoted by len. The minimum value of the length can be 0. The maximum value of the length is not specified in this document. AES128(K,M) AES128(K,M) is the 128bit ciphertext of AES128 for a 128bit key, K, and a 128bit message, M. MAC A 128bit string that is the output of AESCMAC. Denoted by T. Validating the MAC provides assurance of the integrity and authenticity of the message from the source. MAC length By default, the length of the output of AESCMAC is 128 bits. It is possible to truncate the MAC. The result of the truncation should be taken in most significant bits first order. The MAC length must be specified before the communication starts, and it must not be changed during the lifetime of the key.
2.2. Overview

AESCMAC uses the Advanced Encryption Standard [NISTAES] as a building block. To generate a MAC, AESCMAC takes a secret key, a message of variable length, and the length of the message in octets as inputs and returns a fixedbit string called a MAC.
The core of AESCMAC is the basic CBCMAC. For a message, M, to be authenticated, the CBCMAC is applied to M. There are two cases of operation in CMAC. Figure 2.1 illustrates the operation of CBCMAC in both cases. If the size of the input message block is equal to a positive multiple of the block size (namely, 128 bits), the last block shall be exclusiveOR'ed with K1 before processing. Otherwise, the last block shall be padded with 10^i (notation is described in section 2.1) and exclusiveOR'ed with K2. The result of the previous process will be the input of the last encryption. The output of AESCMAC provides data integrity of the whole input message.
++ ++ ++ ++ ++ +++  M_1   M_2   M_n   M_1   M_2  M_n10^i ++ ++ ++ ++ ++ +++    ++    ++  +>(+) +>(+)<K1  +>(+) +>(+)<K2      ++      ++ ++  ++  ++ ++  ++  ++ AES_K  AES_K  AES_K AES_K  AES_K  AES_K ++  ++  ++ ++  ++  ++           ++ ++  ++ ++    ++ ++  T   T  ++ ++ (a) positive multiple block length (b) otherwise
Figure 2.1. Illustration of the two cases of AESCMAC

AES_K is AES128 with key K.
The message M is divided into blocks M_1,...,M_n,
where M_i is the ith message block.
The length of M_i is 128 bits for i = 1,...,n1, and
the length of the last block, M_n, is less than or equal to 128 bits. K1 is the subkey for the case (a), and
K2 is the subkey for the case (b).
K1 and K2 are generated by the subkey generation algorithm described in section 2.3.
2.3. Subkey Generation Algorithm

The subkey generation algorithm, Generate_Subkey(), takes a secret key, K, which is just the key for AES128.
The outputs of the subkey generation algorithm are two subkeys, K1 and K2. We write (K1,K2) := Generate_Subkey(K).
Subkeys K1 and K2 are used in both MAC generation and MAC verification algorithms. K1 is used for the case where the length of the last block is equal to the block length. K2 is used for the case where the length of the last block is less than the block length.
Figure 2.2 specifies the subkey generation algorithm.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + Algorithm Generate_Subkey + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + + + Input : K (128bit key) + + Output : K1 (128bit first subkey) + + K2 (128bit second subkey) + ++ + + + Constants: const_Zero is 0x00000000000000000000000000000000 + + const_Rb is 0x00000000000000000000000000000087 + + Variables: L for output of AES128 applied to 0^128 + + + + Step 1. L := AES128(K, const_Zero); + + Step 2. if MSB(L) is equal to 0 + + then K1 := L << 1; + + else K1 := (L << 1) XOR const_Rb; + + Step 3. if MSB(K1) is equal to 0 + + then K2 := K1 << 1; + + else K2 := (K1 << 1) XOR const_Rb; + + Step 4. return K1, K2; + + + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Figure 2.2. Algorithm Generate_Subkey

In step 1, AES128 with key K is applied to an allzero input block.
In step 2, K1 is derived through the following operation:
If the most significant bit of L is equal to 0, K1 is the leftshift of L by 1 bit.
Otherwise, K1 is the exclusiveOR of const_Rb and the leftshift of L by 1 bit.
In step 3, K2 is derived through the following operation:
If the most significant bit of K1 is equal to 0, K2 is the leftshift of K1 by 1 bit.
Otherwise, K2 is the exclusiveOR of const_Rb and the leftshift of K1 by 1 bit.
In step 4, (K1,K2) := Generate_Subkey(K) is returned.
The mathematical meaning of the procedures in steps 2 and 3, including const_Rb, can be found in [OMAC1a].
2.4. MAC Generation Algorithm

The MAC generation algorithm, AESCMAC(), takes three inputs, a secret key, a message, and the length of the message in octets. The secret key, denoted by K, is just the key for AES128. The message and its length in octets are denoted by M and len, respectively. The message M is denoted by the sequence of M_i, where M_i is the ith message block. That is, if M consists of n blocks, then M is written as
 M = M_1  M_2  ...  M_{n1}  M_n
The length of M_i is 128 bits for i = 1,...,n1, and the length of the last block M_n is less than or equal to 128 bits.
The output of the MAC generation algorithm is a 128bit string, called a MAC, which is used to validate the input message. The MAC is denoted by T, and we write T := AESCMAC(K,M,len). Validating the MAC provides assurance of the integrity and authenticity of the message from the source.
It is possible to truncate the MAC. According to [NISTCMAC], at least a 64bit MAC should be used as protection against guessing attacks. The result of truncation should be taken in most significant bits first order.
The block length of AES128 is 128 bits (16 octets). There is a special treatment if the length of the message is not a positive multiple of the block length. The special treatment is to pad M with the bitstring 10^i to adjust the length of the last block up to the block length.
For an input string x of roctets, where 0 <= r < 16, the padding function, padding(x), is defined as follows:
 padding(x) = x  10^i where i is 1288*r1
That is, padding(x) is the concatenation of x and a single '1', followed by the minimum number of '0's, so that the total length is equal to 128 bits.
Figure 2.3 describes the MAC generation algorithm.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + Algorithm AESCMAC + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + + + Input : K ( 128bit key ) + + : M ( message to be authenticated ) + + : len ( length of the message in octets ) + + Output : T ( message authentication code ) + + + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + Constants: const_Zero is 0x00000000000000000000000000000000 + + const_Bsize is 16 + + + + Variables: K1, K2 for 128bit subkeys + + M_i is the ith block (i=1..ceil(len/const_Bsize)) + + M_last is the last block xored with K1 or K2 + + n for number of blocks to be processed + + r for number of octets of last block + + flag for denoting if last block is complete or not + + + + Step 1. (K1,K2) := Generate_Subkey(K); + + Step 2. n := ceil(len/const_Bsize); + + Step 3. if n = 0 + + then + + n := 1; + + flag := false; + + else + + if len mod const_Bsize is 0 + + then flag := true; + + else flag := false; + + + + Step 4. if flag is true + + then M_last := M_n XOR K1; + + else M_last := padding(M_n) XOR K2; + + Step 5. X := const_Zero; + + Step 6. for i := 1 to n1 do + + begin + + Y := X XOR M_i; + + X := AES128(K,Y); + + end + + Y := M_last XOR X; + + T := AES128(K,Y); + + Step 7. return T; + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Figure 2.3. Algorithm AESCMAC

In step 1, subkeys K1 and K2 are derived from K through the subkey generation algorithm.
In step 2, the number of blocks, n, is calculated. The number of blocks is the smallest integer value greater than or equal to the quotient determined by dividing the length parameter by the block length, 16 octets.
In step 3, the length of the input message is checked. If the input length is 0 (null), the number of blocks to be processed shall be 1, and the flag shall be marked as notcompleteblock (false). Otherwise, if the last block length is 128 bits, the flag is marked as completeblock (true); else mark the flag as notcompleteblock (false).
In step 4, M_last is calculated by exclusiveOR'ing M_n and one of the previously calculated subkeys. If the last block is a complete block (true), then M_last is the exclusiveOR of M_n and K1. Otherwise, M_last is the exclusiveOR of padding(M_n) and K2.
In step 5, the variable X is initialized.
In step 6, the basic CBCMAC is applied to M_1,...,M_{n1},M_last.
In step 7, the 128bit MAC, T := AESCMAC(K,M,len), is returned.
If necessary, the MAC is truncated before it is returned.
2.5. MAC Verification Algorithm

The verification of the MAC is simply done by a MAC recomputation. We use the MAC generation algorithm, which is described in section 2.4.
The MAC verification algorithm, Verify_MAC(), takes four inputs, a secret key, a message, the length of the message in octets, and the received MAC. These are denoted by K, M, len, and T', respectively.
The output of the MAC verification algorithm is either INVALID or VALID.
Figure 2.4 describes the MAC verification algorithm.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + Algorithm Verify_MAC + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ + + + Input : K ( 128bit Key ) + + : M ( message to be verified ) + + : len ( length of the message in octets ) + + : T' ( the received MAC to be verified ) + + Output : INVALID or VALID + + + ++ + + + Step 1. T* := AESCMAC(K,M,len); + + Step 2. if T* is equal to T' + + then + + return VALID; + + else + + return INVALID; + +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Figure 2.4. Algorithm Verify_MAC

In step 1, T* is derived from K, M, and len through the MAC generation algorithm.
In step 2, T* and T' are compared. If T* is equal to T', then return VALID; otherwise return INVALID.
If the output is INVALID, then the message is definitely not authentic, i.e., it did not originate from a source that executed the generation process on the message to produce the purported MAC.
If the output is VALID, then the design of the AESCMAC provides assurance that the message is authentic and, hence, was not corrupted in transit; however, this assurance, as for any MAC algorithm, is not absolute.
3. Security Considerations

The security provided by AESCMAC is built on the strong cryptographic algorithm AES. However, as is true with any cryptographic algorithm, part of its strength lies in the secret key, K, and the correctness of the implementation in all of the participating systems. If the secret key is compromised or inappropriately shared, it guarantees neither authentication nor integrity of message at all. The secret key shall be generated in a way that meets the pseudo randomness requirement of RFC 4086 [RFC4086] and should be kept safe. If and only if AESCMAC is used properly it provides the authentication and integrity that meet the best current practice of message authentication.
4. Test Vectors

The following test vectors are the same as those of [NISTCMAC]. The following vectors are also the output of the test program in Appendix A.
 Subkey Generation K 2b7e1516 28aed2a6 abf71588 09cf4f3c AES128(key,0) 7df76b0c 1ab899b3 3e42f047 b91b546f K1 fbeed618 35713366 7c85e08f 7236a8de K2 f7ddac30 6ae266cc f90bc11e e46d513b   Example 1: len = 0 M <empty string> AESCMAC bb1d6929 e9593728 7fa37d12 9b756746  Example 2: len = 16 M 6bc1bee2 2e409f96 e93d7e11 7393172a AESCMAC 070a16b4 6b4d4144 f79bdd9d d04a287c  Example 3: len = 40 M 6bc1bee2 2e409f96 e93d7e11 7393172a ae2d8a57 1e03ac9c 9eb76fac 45af8e51 30c81c46 a35ce411 AESCMAC dfa66747 de9ae630 30ca3261 1497c827  Example 4: len = 64 M 6bc1bee2 2e409f96 e93d7e11 7393172a ae2d8a57 1e03ac9c 9eb76fac 45af8e51 30c81c46 a35ce411 e5fbc119 1a0a52ef f69f2445 df4f9b17 ad2b417b e66c3710 AESCMAC 51f0bebf 7e3b9d92 fc497417 79363cfe 
5. Acknowledgement

Portions of the text herein are borrowed from [NISTCMAC]. We appreciate the OMAC1 authors, the SP 80038B author, and Russ Housley for his useful comments and guidance, which have been incorporated herein. We also thank Alfred Hoenes for many useful comments. This memo was prepared while Tetsu Iwata was at Ibaraki University, Japan.
We acknowledge the support from the following grants: Collaborative Technology Alliance (CTA) from US Army Research Laboratory, DAAD19 0120011; Presidential Award from Army Research Office, W911NF05 10491; NSF CAREER ANI0093187. Results do not reflect any position of the funding agencies.
6. References
6.1. Normative References

[NISTCMAC] NIST, Special Publication 80038B, "Recommendation for Block Cipher Modes of Operation: The CMAC Mode for Authentication", May 2005. [NISTAES] NIST, FIPS 197, "Advanced Encryption Standard (AES)", November 2001. http://csrc.nist.gov/publications/fips/fips197/fips 197.pdf [RFC4086] Eastlake, D., 3rd, Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, June 2005.
6.2. Informative References

[RFCHMAC] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: KeyedHashing for Message Authentication", RFC 2104, February 1997. [OMAC1a] Tetsu Iwata and Kaoru Kurosawa, "OMAC: OneKey CBC MAC", Fast Software Encryption, FSE 2003, LNCS 2887, pp. 129 153, SpringerVerlag, 2003. [OMAC1b] Tetsu Iwata and Kaoru Kurosawa, "OMAC: OneKey CBC MAC", Submission to NIST, December 2002. Available from the NIST modes of operation web site at http://csrc.nist.gov/CryptoToolkit/modes/proposedmodes/ omac/omacspec.pdf [XCBCa] John Black and Phillip Rogaway, "A Suggestion for Handling ArbitraryLength Messages with the CBC MAC", NIST Second Modes of Operation Workshop, August 2001. Available from the NIST modes of operation web site at http://csrc.nist.gov/CryptoToolkit/modes/proposedmodes/ xcbcmac/xcbcmacspec.pdf [XCBCb] John Black and Phillip Rogaway, "CBC MACs for Arbitrary Length Messages: The ThreeKey Constructions", Journal of Cryptology, Vol. 18, No. 2, pp. 111132, SpringerVerlag, Spring 2005.
Appendix A. Test Code

This C source is designed to generate the test vectors that appear in this memo to verify correctness of the algorithm. The source code is not intended for use in commercial products.
/****************************************************************/ /* AESCMAC with AES128 bit */ /* CMAC Algorithm described in SP80038B */ /* Author: Junhyuk Song (junhyuk.song@samsung.com) */ /* Jicheol Lee (jicheol.lee@samsung.com) */ /****************************************************************/ #include <stdio.h> /* For CMAC Calculation */ unsigned char const_Rb[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87 }; unsigned char const_Zero[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; /* Basic Functions */ void xor_128(unsigned char *a, unsigned char *b, unsigned char *out) { int i; for (i=0;i<16; i++) { out[i] = a[i] ^ b[i]; } } void print_hex(char *str, unsigned char *buf, int len) { int i; for ( i=0; i<len; i++ ) { if ( (i % 16) == 0 && i != 0 ) printf(str); printf("%02x", buf[i]); if ( (i % 4) == 3 ) printf(" "); if ( (i % 16) == 15 ) printf("\n"); } if ( (i % 16) != 0 ) printf("\n"); } void print128(unsigned char *bytes) { int j; for (j=0; j<16;j++) { printf("%02x",bytes[j]); if ( (j%4) == 3 ) printf(" "); } } void print96(unsigned char *bytes) { int j; for (j=0; j<12;j++) { printf("%02x",bytes[j]); if ( (j%4) == 3 ) printf(" "); } } /* AESCMAC Generation Function */ void leftshift_onebit(unsigned char *input,unsigned char *output) { int i; unsigned char overflow = 0; for ( i=15; i>=0; i ) { output[i] = input[i] << 1; output[i] = overflow; overflow = (input[i] & 0x80)?1:0; } return; } void generate_subkey(unsigned char *key, unsigned char *K1, unsigned char *K2) { unsigned char L[16]; unsigned char Z[16]; unsigned char tmp[16]; int i; for ( i=0; i<16; i++ ) Z[i] = 0; AES_128(key,Z,L); if ( (L[0] & 0x80) == 0 ) { /* If MSB(L) = 0, then K1 = L << 1 */ leftshift_onebit(L,K1); } else { /* Else K1 = ( L << 1 ) (+) Rb */ leftshift_onebit(L,tmp); xor_128(tmp,const_Rb,K1); } if ( (K1[0] & 0x80) == 0 ) { leftshift_onebit(K1,K2); } else { leftshift_onebit(K1,tmp); xor_128(tmp,const_Rb,K2); } return; } void padding ( unsigned char *lastb, unsigned char *pad, int length ) { int j; /* original last block */ for ( j=0; j<16; j++ ) { if ( j < length ) { pad[j] = lastb[j]; } else if ( j == length ) { pad[j] = 0x80; } else { pad[j] = 0x00; } } } void AES_CMAC ( unsigned char *key, unsigned char *input, int length, unsigned char *mac ) { unsigned char X[16],Y[16], M_last[16], padded[16]; unsigned char K1[16], K2[16]; int n, i, flag; generate_subkey(key,K1,K2); n = (length+15) / 16; /* n is number of rounds */ if ( n == 0 ) { n = 1; flag = 0; } else { if ( (length%16) == 0 ) { /* last block is a complete block */ flag = 1; } else { /* last block is not complete block */ flag = 0; } } if ( flag ) { /* last block is complete block */ xor_128(&input[16*(n1)],K1,M_last); } else { padding(&input[16*(n1)],padded,length%16); xor_128(padded,K2,M_last); } for ( i=0; i<16; i++ ) X[i] = 0; for ( i=0; i<n1; i++ ) { xor_128(X,&input[16*i],Y); /* Y := Mi (+) X */ AES_128(key,Y,X); /* X := AES128(KEY, Y); */ } xor_128(X,M_last,Y); AES_128(key,Y,X); for ( i=0; i<16; i++ ) { mac[i] = X[i]; } }
int main()
{unsigned char L[16], K1[16], K2[16], T[16], TT[12]; unsigned char M[64] = { 0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a, 0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51, 0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef, 0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10 }; unsigned char key[16] = { 0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c }; printf("\n"); printf("K "); print128(key); printf("\n"); printf("\nSubkey Generation\n"); AES_128(key,const_Zero,L); printf("AES_128(key,0) "); print128(L); printf("\n"); generate_subkey(key,K1,K2); printf("K1 "); print128(K1); printf("\n"); printf("K2 "); print128(K2); printf("\n"); printf("\nExample 1: len = 0\n"); printf("M "); printf("<empty string>\n"); AES_CMAC(key,M,0,T); printf("AES_CMAC "); print128(T); printf("\n"); printf("\nExample 2: len = 16\n"); printf("M "); print_hex(" ",M,16); AES_CMAC(key,M,16,T); printf("AES_CMAC "); print128(T); printf("\n"); printf("\nExample 3: len = 40\n"); printf("M "); print_hex(" ",M,40); AES_CMAC(key,M,40,T); printf("AES_CMAC "); print128(T); printf("\n"); printf("\nExample 4: len = 64\n"); printf("M "); print_hex(" ",M,64); AES_CMAC(key,M,64,T); printf("AES_CMAC "); print128(T); printf("\n"); printf("\n"); return 0; }
Authors' Addresses

Junhyuk Song
University of Washington
Samsung ElectronicsPhone: (206) 8535843 EMail: songlee@ee.washington.edu, junhyuk.song@samsung.com
Jicheol Lee
Samsung ElectronicsPhone: +82312793605 EMail: jicheol.lee@samsung.com
Radha Poovendran
Network Security Lab
University of WashingtonPhone: (206) 2216512 EMail: radha@ee.washington.edu
Tetsu Iwata
Nagoya UniversityEMail: iwata@cse.nagoyau.ac.jp
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