diff options
Diffstat (limited to 'libtomcrypt/src/encauth/ocb/ocb_init.c')
| -rw-r--r-- | libtomcrypt/src/encauth/ocb/ocb_init.c | 133 |
1 files changed, 133 insertions, 0 deletions
diff --git a/libtomcrypt/src/encauth/ocb/ocb_init.c b/libtomcrypt/src/encauth/ocb/ocb_init.c new file mode 100644 index 0000000..9266d5c --- /dev/null +++ b/libtomcrypt/src/encauth/ocb/ocb_init.c @@ -0,0 +1,133 @@ +/* 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, tomstdenis@gmail.com, http://libtomcrypt.org + */ + +/** + @file ocb_init.c + OCB implementation, initialize state, by Tom St Denis +*/ +#include "tomcrypt.h" + +#ifdef OCB_MODE + +static const struct { + int len; + unsigned char poly_div[MAXBLOCKSIZE], + poly_mul[MAXBLOCKSIZE]; +} polys[] = { +{ + 8, + { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0D }, + { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1B } +}, { + 16, + { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x43 }, + { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87 } +} +}; + +/** + Initialize an OCB context. + @param ocb [out] The destination of the OCB state + @param cipher The index of the desired cipher + @param key The secret key + @param keylen The length of the secret key (octets) + @param nonce The session nonce (length of the block size of the cipher) + @return CRYPT_OK if successful +*/ +int ocb_init(ocb_state *ocb, int cipher, + const unsigned char *key, unsigned long keylen, const unsigned char *nonce) +{ + int poly, x, y, m, err; + + LTC_ARGCHK(ocb != NULL); + LTC_ARGCHK(key != NULL); + LTC_ARGCHK(nonce != NULL); + + /* valid cipher? */ + if ((err = cipher_is_valid(cipher)) != CRYPT_OK) { + return err; + } + + /* determine which polys to use */ + ocb->block_len = cipher_descriptor[cipher].block_length; + for (poly = 0; poly < (int)(sizeof(polys)/sizeof(polys[0])); poly++) { + if (polys[poly].len == ocb->block_len) { + break; + } + } + if (polys[poly].len != ocb->block_len) { + return CRYPT_INVALID_ARG; + } + + /* schedule the key */ + if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ocb->key)) != CRYPT_OK) { + return err; + } + + /* find L = E[0] */ + zeromem(ocb->L, ocb->block_len); + cipher_descriptor[cipher].ecb_encrypt(ocb->L, ocb->L, &ocb->key); + + /* find R = E[N xor L] */ + for (x = 0; x < ocb->block_len; x++) { + ocb->R[x] = ocb->L[x] ^ nonce[x]; + } + cipher_descriptor[cipher].ecb_encrypt(ocb->R, ocb->R, &ocb->key); + + /* find Ls[i] = L << i for i == 0..31 */ + XMEMCPY(ocb->Ls[0], ocb->L, ocb->block_len); + for (x = 1; x < 32; x++) { + m = ocb->Ls[x-1][0] >> 7; + for (y = 0; y < ocb->block_len-1; y++) { + ocb->Ls[x][y] = ((ocb->Ls[x-1][y] << 1) | (ocb->Ls[x-1][y+1] >> 7)) & 255; + } + ocb->Ls[x][ocb->block_len-1] = (ocb->Ls[x-1][ocb->block_len-1] << 1) & 255; + + if (m == 1) { + for (y = 0; y < ocb->block_len; y++) { + ocb->Ls[x][y] ^= polys[poly].poly_mul[y]; + } + } + } + + /* find Lr = L / x */ + m = ocb->L[ocb->block_len-1] & 1; + + /* shift right */ + for (x = ocb->block_len - 1; x > 0; x--) { + ocb->Lr[x] = ((ocb->L[x] >> 1) | (ocb->L[x-1] << 7)) & 255; + } + ocb->Lr[0] = ocb->L[0] >> 1; + + if (m == 1) { + for (x = 0; x < ocb->block_len; x++) { + ocb->Lr[x] ^= polys[poly].poly_div[x]; + } + } + + /* set Li, checksum */ + zeromem(ocb->Li, ocb->block_len); + zeromem(ocb->checksum, ocb->block_len); + + /* set other params */ + ocb->block_index = 1; + ocb->cipher = cipher; + + return CRYPT_OK; +} + +#endif + +/* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_init.c,v $ */ +/* $Revision: 1.3 $ */ +/* $Date: 2005/05/05 14:35:58 $ */ |