Problem - Kevin Tafuro

#include
#include
#include
/* Returns 0 when malloc() fails. */
unsigned char *spc_digest_message(EVP_MD *type, unsigned char *in,
unsigned long n, unsigned int *outlen) {
EVP_MD_CTX ctx;
unsigned char *ret;
EVP_DigestInit(&ctx, type);
EVP_DigestUpdate(&ctx, in, n);
if (!(ret = (unsigned char *)malloc(EVP_MD_CTX_size(&ctx))) return 0;
EVP_DigestFinal(&ctx, ret, outlen);
return ret;
}
Here’s a simple example that uses the previous wrapper:
#include
#include
#include
#include
int main(int argc, char *argv[ ]) {
int i;
unsigned int ol;
unsigned char *s = "Testing...1...2...3...";
unsigned char *r;
r = spc_digest_message(EVP_sha1( ), s, strlen(s), &ol);
printf("SHA1(\"%s\") = ", s);
for (i = 0; i < ol; i++) printf("%02x", r[i]);
printf("\n");
free(r);
return 0;
}
Such a wrapper can be adapted easily to any incremental hashing API, simply by
changing the names of the functions and the underlying data type, and removing the
first argument of the wrapper if it is not necessary. Here is the same wrapper implemented
using Microsoft’s CryptoAPI:
#include
#include
BYTE *SpcDigestMessage(ALG_ID Algid, BYTE *pbIn, DWORD cbIn, DWORD *cbOut) {
BYTE *pbOut;
DWORD cbData = sizeof(DWORD);
HCRYPTHASH hHash;
HCRYPTPROV hProvider;
268 | Chapter 6: Hashes and Message Authentication
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