SHA-1 or SHA1 is a one-way hash function;
it computes a 160-bit message digest.
SHA-1 often appears in security protocols; for example,
many HTTPS websites use RSA with SHA-1 to secure their connections.
BitTorrent uses SHA-1 to verify downloads.
Git and Mercurial use SHA-1 digests to identify commits.

A US government standard, FIPS 180-1, defines SHA-1.

Find the SHA-1 message digest for a string of octets. You may either call a SHA-1 library, or implement SHA-1 in your language. Both approaches interest Rosetta Code.



 Warning: SHA-1 has known weaknesses. Theoretical attacks may find a collision after 252 operations, or perhaps fewer.
This is much faster than a brute force attack of 280 operations. USgovernment deprecated SHA-1.
For production-grade cryptography, users may consider a stronger alternative, such as SHA-256 (from the SHA-2 family) or the upcoming SHA-3.


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/sha.h>
 
int main()
{
  int i;
  unsigned char result[SHA_DIGEST_LENGTH];
  const char *string = "Rosetta Code";
 
  SHA1(string, strlen(string), result);
 
  for(i = 0; i < SHA_DIGEST_LENGTH; i++)
    printf("%02x%c", result[i], i < (SHA_DIGEST_LENGTH-1) ? ' ' : '\n');
 
  return EXIT_SUCCESS;
}