Problem - Kevin Tafuro

eturn 0;
}
Every hash function that OpenSSLsupports has a similar API. In addition, every
such function has an “all-in-one” API that allows you to combine the work of calls
for initialization, updating, and finalization, obviating the need for a context object:
unsigned char *SHA1(unsigned char *in, unsigned long len, unsigned char *out);
This function returns a pointer to the out argument.
Both the incremental API and the all-in-one API are very standard, even beyond
OpenSSL. The reference versions of most hash algorithms look incredibly similar. In
fact, Microsoft’s CryptoAPI for Windows provides a very similar API. Any of the
Microsoft CSPs provide implementations of MD2, MD5, and SHA1. The following
code is the CryptoAPI version of the OpenSSL code presented previously:
#include
#include
#include
int main(int argc, char *argv[ ]) {
BYTE *pbData;
DWORD cbData = sizeof(DWORD), cbHashSize, i;
HCRYPTHASH hSHA1;
HCRYPTPROV hProvider;
unsigned char *s1 = "Testing";
unsigned char *s2 = "...1...2...3...";
CryptAcquireContext(&hProvider, 0, MS_DEF_PROV, PROV_RSA_FULL, 0);
CryptCreateHash(hProvider, CALG_SHA1, 0, 0, &hSHA1);
CryptHashData(hSHA1, s1, strlen(s1), 0);
CryptHashData(hSHA1, s2, strlen(s2), 0);
CryptGetHashParam(hSHA1, HP_HASHSIZE, (BYTE *)&cbHashSize, &cbData, 0);
pbData = (BYTE *)LocalAlloc(LMEM_FIXED, cbHashSize);
CryptGetHashParam(hSHA1, HP_HASHVAL, pbData, &cbHashSize, 0);
CryptDestroyHash(hSHA1);
CryptReleaseContext(hProvider, 0);
printf("SHA1(\"%s%s\") = ", s1, s2);
for (i = 0; i < cbHashSize; i++) printf("%02x", pbData[i]);
printf("\n");
LocalFree(pbData);
return 0;
}
The preferred API for accessing hash functions from OpenSSL, though, is the EVP
API, which provides a generic API to all of the hash functions OpenSSLsupports.
The following code does the same thing as the first example with the EVP interface
instead of the SHA1 interface:
#include
#include
264 | Chapter 6: Hashes and Message Authentication
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