Problem - Kevin Tafuro

EVP_DigestFinal(&ctx, result, &ol);
printf("SHA1(\"%s%s\") = ", s1, s2);
for (i = 0; i < ol; i++) printf("%02x", result[i]);
printf("\n");
free(result);
return 0;
}
The OpenSSLlibrary supports only two cryptographic hash functions that we recommend,
SHA1 and RIPEMD-160. It also supports MD2, MD4, MD5, and MDC-2-
DES. MDC-2-DES is reasonable, but it is slow and provides only 64 bits of resistance
to birthday attacks, whereas we recommend a minimum baseline of 80 bits of
security. As an alternative, you could initialize the hash function with a nonce, as discussed
in Recipe 6.8.
Nonetheless, Table 6-3 contains a summary of the necessary information on each
hash function to use both the EVP and hash-specific APIs with OpenSSL.
Table 6-3. OpenSSL-supported hash functions
Message
digest function
EVP function to
specify MD
Context type for
MD-specific API
Of course, you may want to use an off-the-shelf hash function that isn’t supported by
either OpenSSLor CryptoAPI—for example, SHA-256, SHA-384, or SHA-512. Aaron
Gifford has produced a good, free library with implementations of these functions and
released it under a BSD-style license. It is available from http://www.aarongifford.com/
computers/sha.html.
That library exports an API that should look very familiar:
SHA256_Init(SHA256_CTX *ctx);
SHA256_Update(SHA256_CTX *ctx, unsigned char *data, size_t inlen);
SHA256_Final(unsigned char out[SHA256_DIGEST_LENGTH], SHA256_CTX *ctx);
SHA384_Init(SHA384_CTX *ctx);
SHA384_Update(SHA384_CTX *ctx, unsigned char *data, size_t inlen);
SHA384_Final(unsigned char out[SHA384_DIGEST_LENGTH], SHA384_CTX *ctx);
SHA512_Init(SHA512_CTX *ctx);
SHA512_Update(SHA512_CTX *ctx, unsigned char *data, size_t inlen);
SHA512_Final(unsigned char out[SHA512_DIGEST_LENGTH], SHA512_CTX *ctx);
All of the previous functions are prototyped in the sha2.h header file.
266 | Chapter 6: Hashes and Message Authentication
Prefix for MD-specific API
calls (i.e., XXX_Init, …)
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.
Include file for MDspecific
API
MD2 EVP_md2() MD2_CTX MD2 openssl/md2.h
MD4 EVP_md4() MD4_CTX MD4 openssl/md4.h
MD5 EVP_md5() MD5_CTX MD5 openssl/md5.h
MDC-2-DES EVP_mdc2() MDC2_CTX MDC2 openssl/mdc2.h
RIPEMD-160 EVP_ripemd160() RIPEMD160_CTX RIPEMD160 openssl/ripemd.h
SHA1 EVP_sha1() SHA_CTX SHA1 openssl/sha.h