Problem - Kevin Tafuro

if (klen inner[i] ^= key[i];
ctx->outer[i] ^= key[i];
}
} else {
DGST_Update(&(ctx->mdctx), key, klen);
DGST_Final(dk, &(ctx->mdctx));
DGST_Reset(&(ctx->mdctx));
for (i = 0; i < DGST_OUT_SZ; i++) {
ctx->inner[i] ^= dk[i];
ctx->outer[i] ^= dk[i];
}
}
DGST_Update(&(ctx->mdctx), ctx->inner, DGST_BLK_SZ);
}
void SPC_HMAC_Reset(SPC_HMAC_CTX *ctx) {
DGST_Reset(&(ctx->mdctx));
DGST_Update(&(ctx->mdctx), ctx->inner, DGST_BLK_SZ);
}
void SPC_HMAC_Update(SPC_HMAC_CTX *ctx, unsigned char *m, size_t l) {
DGST_Update(&(ctx->mdctx), m, l);
}
void SPC_HMAC_Final(unsigned char *tag, SPC_HMAC_CTX *ctx) {
unsigned char is[DGST_OUT_SZ];
DGST_Final(is, &(ctx->mdctx));
DGST_Reset(&(ctx->mdctx));
DGST_Update(&(ctx->mdctx), ctx->outer, DGST_BLK_SZ);
DGST_Update(&(ctx->mdctx), is, DGST_OUT_SZ);
DGST_Final(tag, &(ctx->mdctx));
}
void SPC_HMAC_Cleanup(SPC_HMAC_CTX *ctx) {
volatile char *p = ctx->inner;
volatile char *q = ctx->outer;
int i;
for (i = 0; i < DGST_BLK_SZ; i++) *p++ = *q++ = 0;
}
The previous code does require a particular interface to a hash function interface.
First, it requires two constants: DGST_BLK_SZ, which is the internal block size of the
underlying hash function (see Recipe 6.3), and DGST_OUT_SZ, which is the size of the
resulting message digest. Second, it requires a context type for the message digest,
which you should typedef to DGST_CTX. Finally, it requires an incremental interface to
the hash function:
void DGST_Init(DGST_CTX *ctx);
void DGST_Reset(DGST_CTX *ctx);
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