Add examples to EVP_EncryptInit manual page.

 int key_bits;

 EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_SET_RC2_KEY_BITS, key_bits, NULL);

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_EncryptInit(&ctx, EVP_bf_cbc(), 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(&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;

	}

The ciphertext from the above example can be decrypted using the B<openssl>

utility with the command line:

 S<openssl bf -in cipher.bin -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708 -d>

General encryption, decryption function example using FILE I/O and RC2 with an

80 bit key:

 int do_crypt(FILE *in, FILE *out, int do_encrypt)

 	{

	/* Allow enough space in output buffer for additional block */

	inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];

	int inlen, outlen;

	/* Bogus key and IV: we'd normally set these from

	 * another source.

	 */

	unsigned char key[] = "0123456789";

	unsigned char iv[] = "12345678";

	/* Don't set key or IV because we will modify the parameters */

	EVP_CipherInit(&ctx, EVP_rc2(), NULL, NULL, do_encrypt);

	EVP_CIPHER_CTX_set_key_length(&ctx, 10);

	/* We finished modifying parameters so now we can set key and IV */

	EVP_CipherInit(&ctx, NULL, key, iv, do_encrypt);

	for(;;) 

		{

		inlen = fread(inbuf, 1, 1024, in);

		if(inlen <= 0) break;

		if(!EVP_CipherUpdate(&ctx, outbuf, &outlen, inbuf, inlen))

			{

			/* Error */

			return 0;

			}

		fwrite(outbuf, 1, outlen, out);

		}

	if(!EVP_CipherFinal(&ctx, outbuf, &outlen))

		{

		/* Error */

		return 0;

		}

	fwrite(outbuf, 1, outlen, out);

	EVP_CIPHER_CTX_cleanup(&ctx);

	return 1;

	}

=head1 SEE ALSO

L<evp(3)|evp(3)>