Problem - Kevin Tafuro

*/
if (ctx->ix) {
while (ctx->ix < SPC_BLOCK_SZ) --il, ctx->iv[ctx->ix++] ^= *in++;
SPC_DO_ENCRYPT(&(ctx->ks), ctx->iv, ctx->iv);
for (i = 0; i < SPC_BLOCK_SZ / sizeof(int); i++)
((unsigned int *)out)[i] = ((unsigned int *)(ctx->iv))[i];
out += SPC_BLOCK_SZ;
}
/* Operate on word-sized chunks, because it's easy to do so. You might gain a
* couple of cycles per loop by unrolling and getting rid of i if you know your
* word size a priori.
*/
while (il >= SPC_BLOCK_SZ) {
for (i = 0; i < SPC_BLOCK_SZ / sizeof(int); i++)
((unsigned int *)(ctx->iv))[i] ^= ((unsigned int *)in)[i];
SPC_DO_ENCRYPT(&(ctx->ks), ctx->iv, ctx->iv);
for (i = 0; i < SPC_BLOCK_SZ / sizeof(int); i++)
((unsigned int *)out)[i] = ((unsigned int *)(ctx->iv))[i];
out += SPC_BLOCK_SZ;
in += SPC_BLOCK_SZ;
il -= SPC_BLOCK_SZ;
}
/* Deal with leftovers... one byte at a time is fine. */
for (i = 0; i < il; i++) ctx->iv[i] ^= in[i];
ctx->ix = il;
if (ol) *ol = out-start;
return 1;
}
The following spc_cbc_encrypt_final( ) function outputs any remaining data and
securely wipes the key material in the context, along with all the intermediate state.
If padding is on, it will output one block. If padding is off, it won’t output anything.
If padding is off and the total length of the input wasn’t a multiple of the block size,
spc_cbc_encrypt_final( ) will return 0. Otherwise, it will always succeed.
int spc_cbc_encrypt_final(SPC_CBC_CTX *ctx, unsigned char *out, size_t *ol) {
int ret;
unsigned char pad;
if (ctx->pad) {
pad = SPC_BLOCK_SZ - ctx->ix;
while (ctx->ix < SPC_BLOCK_SZ) ctx->iv[ctx->ix++] ^= pad;
SPC_DO_ENCRYPT(&(ctx->ks), ctx->iv, out);
spc_memset(ctx, 0, sizeof(SPC_CBC_CTX));
if(ol) *ol = SPC_BLOCK_SZ;
return 1;
}
if(ol) *ol = 0;
ret = !(ctx->ix);
spc_memset(ctx, 0, sizeof(SPC_CBC_CTX));
return ret;
}
182 | Chapter 5: Symmetric Encryption
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