// From: http://www.openssl.org/docs/crypto/EVP_EncryptInit.html
// A simple encryption function, using the EVP interface of OpenSSL
// Compile: gcc -o e0 encrypt0.c -lcrypto
// Run:     ./e0
// Decrypt: openssl bf -d -in cipher0.bin -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

// include the EVP headers
#include <openssl/evp.h>

// see the above URL for this example function, with more explanation
// Encrypt a string using blowfish: 
int do_crypt(char *outfile)
        {
        unsigned char outbuf[1024];
        int outlen, tmplen;
        /* Bogus key and IV: we'd normally set these from
         * another source.
         */
        unsigned char key[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
        unsigned char iv[] = {1,2,3,4,5,6,7,8};
        char intext[] = "Some Crypto Text";
        EVP_CIPHER_CTX ctx;
        FILE *out;
        EVP_CIPHER_CTX_init(&ctx);
        EVP_EncryptInit_ex(&ctx, EVP_bf_cbc(), NULL, key, iv);
        if(!EVP_EncryptUpdate(&ctx, outbuf, &outlen, intext, strlen(intext)))
                {
                /* Error */
                return 0;
                }
        /* Buffer passed to EVP_EncryptFinal() must be after data just
         * encrypted to avoid overwriting it.
         */
        if(!EVP_EncryptFinal_ex(&ctx, outbuf + outlen, &tmplen))
                {
                /* Error */
                return 0;
                }
        outlen += tmplen;
        EVP_CIPHER_CTX_cleanup(&ctx);
        /* Need binary mode for fopen because encrypted data is
         * binary data. Also cannot use strlen() on it because
         * it wont be null terminated and may contain embedded
         * nulls.
         */
        out = fopen(outfile, "wb");
        fwrite(outbuf, 1, outlen, out);
        fclose(out);
        return 1;
        }

// fairly minimal main function, driving the encryption
main () {
  // output file
  static char filename[80] = "cipher0.bin";
  // explain what's happening
  printf("Encrypting some hard-wired text to file %s\n", filename);
  // call the main encryption function
  do_crypt(filename);
}