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      1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
      2  *
      3  * LibTomCrypt is a library that provides various cryptographic
      4  * algorithms in a highly modular and flexible manner.
      5  *
      6  * The library is free for all purposes without any express
      7  * guarantee it works.
      8  *
      9  * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com
     10  */
     11 
     12 /**
     13     @file eax_decrypt.c
     14     EAX implementation, decrypt block, by Tom St Denis
     15 */
     16 #include "tomcrypt.h"
     17 
     18 #ifdef EAX_MODE
     19 
     20 /**
     21    Decrypt data with the EAX protocol
     22    @param eax     The EAX state
     23    @param ct      The ciphertext
     24    @param pt      [out] The plaintext
     25    @param length  The length (octets) of the ciphertext
     26    @return CRYPT_OK if successful
     27 */
     28 int eax_decrypt(eax_state *eax, const unsigned char *ct, unsigned char *pt,
     29                 unsigned long length)
     30 {
     31    int err;
     32 
     33    LTC_ARGCHK(eax != NULL);
     34    LTC_ARGCHK(pt  != NULL);
     35    LTC_ARGCHK(ct  != NULL);
     36 
     37    /* omac ciphertext */
     38    if ((err = omac_process(&eax->ctomac, ct, length)) != CRYPT_OK) {
     39       return err;
     40    }
     41 
     42    /* decrypt  */
     43    return ctr_decrypt(ct, pt, length, &eax->ctr);
     44 }
     45 
     46 #endif
     47 
     48 /* $Source: /cvs/libtom/libtomcrypt/src/encauth/eax/eax_decrypt.c,v $ */
     49 /* $Revision: 1.4 $ */
     50 /* $Date: 2006/03/31 14:15:35 $ */
     51