Mercurial > dropbear
diff s_ocb_done.c @ 0:d7da3b1e1540 libtomcrypt
put back the 0.95 makefile which was inadvertently merged over
author | Matt Johnston <matt@ucc.asn.au> |
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date | Mon, 31 May 2004 18:21:40 +0000 |
parents | |
children | 5d99163f7e32 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/s_ocb_done.c Mon May 31 18:21:40 2004 +0000 @@ -0,0 +1,102 @@ +/* LibTomCrypt, modular cryptographic library -- Tom St Denis + * + * LibTomCrypt is a library that provides various cryptographic + * algorithms in a highly modular and flexible manner. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, [email protected], http://libtomcrypt.org + */ + +/* OCB Implementation by Tom St Denis */ +#include "mycrypt.h" + +#ifdef OCB_MODE + +/* Since the last block is encrypted in CTR mode the same code can + * be used to finish a decrypt or encrypt stream. The only difference + * is we XOR the final ciphertext into the checksum so we have to xor it + * before we CTR [decrypt] or after [encrypt] + * + * the names pt/ptlen/ct really just mean in/inlen/out but this is the way I wrote it... + */ +int __ocb_done(ocb_state *ocb, const unsigned char *pt, unsigned long ptlen, + unsigned char *ct, unsigned char *tag, unsigned long *taglen, int mode) + +{ + unsigned char Z[MAXBLOCKSIZE], Y[MAXBLOCKSIZE], X[MAXBLOCKSIZE]; + int err, x; + + _ARGCHK(ocb != NULL); + _ARGCHK(pt != NULL); + _ARGCHK(ct != NULL); + _ARGCHK(tag != NULL); + _ARGCHK(taglen != NULL); + if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) { + return err; + } + if (ocb->block_len != cipher_descriptor[ocb->cipher].block_length || + (int)ptlen > ocb->block_len || (int)ptlen < 0) { + return CRYPT_INVALID_ARG; + } + + /* compute X[m] = len(pt[m]) XOR Lr XOR Z[m] */ + ocb_shift_xor(ocb, X); + memcpy(Z, X, ocb->block_len); + + X[ocb->block_len-1] ^= (ptlen*8)&255; + X[ocb->block_len-2] ^= ((ptlen*8)>>8)&255; + for (x = 0; x < ocb->block_len; x++) { + X[x] ^= ocb->Lr[x]; + } + + /* Y[m] = E(X[m])) */ + cipher_descriptor[ocb->cipher].ecb_encrypt(X, Y, &ocb->key); + + if (mode == 1) { + /* decrypt mode, so let's xor it first */ + /* xor C[m] into checksum */ + for (x = 0; x < (int)ptlen; x++) { + ocb->checksum[x] ^= ct[x]; + } + } + + /* C[m] = P[m] xor Y[m] */ + for (x = 0; x < (int)ptlen; x++) { + ct[x] = pt[x] ^ Y[x]; + } + + if (mode == 0) { + /* encrypt mode */ + /* xor C[m] into checksum */ + for (x = 0; x < (int)ptlen; x++) { + ocb->checksum[x] ^= ct[x]; + } + } + + /* xor Y[m] and Z[m] into checksum */ + for (x = 0; x < ocb->block_len; x++) { + ocb->checksum[x] ^= Y[x] ^ Z[x]; + } + + /* encrypt checksum, er... tag!! */ + cipher_descriptor[ocb->cipher].ecb_encrypt(ocb->checksum, X, &ocb->key); + + /* now store it */ + for (x = 0; x < ocb->block_len && x < (int)*taglen; x++) { + tag[x] = X[x]; + } + *taglen = x; + +#ifdef CLEAN_STACK + zeromem(X, sizeof(X)); + zeromem(Y, sizeof(Y)); + zeromem(Z, sizeof(Z)); + zeromem(ocb, sizeof(*ocb)); +#endif + return CRYPT_OK; +} + +#endif +