Add examples to EVP_EncryptInit manual page.

doc/crypto/EVP_EncryptInit.pod

@@ -367,6 +367,95 @@ Set the effective key length used in RC2:
  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)>