/* [identical to Skein_256_Init() when keyBytes == 0 && treeInfo == SKEIN_CFG_TREE_INFO_SEQUENTIAL] */
int Skein_256_InitExt(Skein_256_Ctxt_t *ctx,size_t hashBitLen,u64b_t treeInfo, const u08b_t *key, size_t keyBytes)
{
union
{
u08b_t b[SKEIN_256_STATE_BYTES];
u64b_t w[SKEIN_256_STATE_WORDS];
} cfg; /* config block */
Skein_Assert(hashBitLen > 0,SKEIN_BAD_HASHLEN);
Skein_Assert(keyBytes == 0 || key != NULL,SKEIN_FAIL);
/* compute the initial chaining values ctx->X[], based on key */
if (keyBytes == 0) /* is there a key? */
{
memset(ctx->X,0,sizeof(ctx->X)); /* no key: use all zeroes as key for config block */
}
else /* here to pre-process a key */
{
Skein_assert(sizeof(cfg.b) >= sizeof(ctx->X));
/* do a mini-Init right here */
ctx->h.hashBitLen=8*sizeof(ctx->X); /* set output hash bit count = state size */
Skein_Start_New_Type(ctx,KEY); /* set tweaks: T0 = 0; T1 = KEY type */
memset(ctx->X,0,sizeof(ctx->X)); /* zero the initial chaining variables */
Skein_256_Update(ctx,key,keyBytes); /* hash the key */
Skein_256_Final_Pad(ctx,cfg.b); /* put result into cfg.b[] */
memcpy(ctx->X,cfg.b,sizeof(cfg.b)); /* copy over into ctx->X[] */
#if SKEIN_NEED_SWAP
{
uint_t i;
for (i=0;i<SKEIN_256_STATE_WORDS;i++) /* convert key bytes to context words */
ctx->X[i] = Skein_Swap64(ctx->X[i]);
}
#endif
}
/* build/process the config block, type == CONFIG (could be precomputed for each key) */
ctx->h.hashBitLen = hashBitLen; /* output hash bit count */
Skein_Start_New_Type(ctx,CFG_FINAL);
memset(&cfg.w,0,sizeof(cfg.w)); /* pre-pad cfg.w[] with zeroes */
cfg.w[0] = Skein_Swap64(SKEIN_SCHEMA_VER);
cfg.w[1] = Skein_Swap64(hashBitLen); /* hash result length in bits */
cfg.w[2] = Skein_Swap64(treeInfo); /* tree hash config info (or SKEIN_CFG_TREE_INFO_SEQUENTIAL) */
Skein_Show_Key(256,&ctx->h,key,keyBytes);
/* compute the initial chaining values from config block */
Skein_256_Process_Block(ctx,cfg.b,1,SKEIN_CFG_STR_LEN);
/* The chaining vars ctx->X are now initialized */
/* Set up to process the data message portion of the hash (default) */
ctx->h.bCnt = 0; /* buffer b[] starts out empty */
Skein_Start_New_Type(ctx,MSG);
return SKEIN_SUCCESS;
}
uint8_t *
calc_mac(uint8_t *snum, uint8_t *mkey, uint8_t *nonce, int nonce_len)
{
EKeySkein sk_mac;
uint8_t macbuf[32];
uint8_t *mac;
mac = calloc(1, 6);
PrepareSkein(&sk_mac, snum, mkey, EKEY_SKEIN_PERSONALISATION_LKMS);
Skein_256_Update(&sk_mac, nonce, nonce_len);
Skein_256_Final_Pad(&sk_mac, macbuf);
mac[0] = macbuf[0];
mac[1] = macbuf[1];
mac[2] = macbuf[2];
mac[3] = macbuf[29];
mac[4] = macbuf[30];
mac[5] = macbuf[31];
return mac;
}