Hello,
> I have a doubt about how to use the HMAC() function. I developed this
code in C
> language: (abridged)
>
> ...
> unsigned char *auth = NULL;
> unsigned char *session_auth_key;
> unsigned char *auth_tag;
> .
> .
> auth = HMAC(EVP_sha1(), session_auth_key, auth_key_length, length,
> auth_tag, auth_tag_length);
> .
> .
>
> Is the first argument in HMAC correct?
> When i run my program with GDB (GNU Project Debugger ) i get the string
> "EVP_DigestFinal_ex () from /usr/lib/i686/cmov/libcrypto.so.0.9.8" as
result.
> I think that the problem deals with the HMAC function.
> I use also the AES_ctr128_encrypt in my program. Can it have an
influence?
Code like this:
HMAC(EVP_md5(), pass, strlen(pass),
(u_char *) ctx->chal, strlen(ctx->chal), buff, &len);
works (pass and chal are normal strings)
As a result you will get hmac (here of MD5 size = 16bytes) but as binary
buffer.
You may convert this buffer to hex with code:
for (i = 0; i < len; i++) {
sprintf(&(digest[i * 2]), "%02x", buff[i]);
}
digest[2 * len] = 0;
and use for example for ascii compare or so.
(from performance point of view sprintf() should be replaced
with simple function which covert byte to hex form).
Best regards,
--
Marek Marcola <[EMAIL PROTECTED]>
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