+Encrypt a string using IDEA:
+
+ 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_idea_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;
+ }
+
+The ciphertext from the above example can be decrypted using the B<openssl>
+utility with the command line (shown on two lines for clarity):
+
+ openssl idea -d <filename
+ -K 000102030405060708090A0B0C0D0E0F -iv 0102030405060708
+
+General encryption and decryption function example using FILE I/O and AES128
+with a 128-bit key:
+
+ int do_crypt(FILE *in, FILE *out, int do_encrypt)
+ {
+ /* Allow enough space in output buffer for additional block */
+ unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
+ int inlen, outlen;
+ EVP_CIPHER_CTX ctx;
+ /* Bogus key and IV: we'd normally set these from
+ * another source.
+ */
+ unsigned char key[] = "0123456789abcdeF";
+ unsigned char iv[] = "1234567887654321";
+
+ /* Don't set key or IV right away; we want to check lengths */
+ EVP_CIPHER_CTX_init(&ctx);
+ EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,
+ do_encrypt);
+ OPENSSL_assert(EVP_CIPHER_CTX_key_length(&ctx) == 16);
+ OPENSSL_assert(EVP_CIPHER_CTX_iv_length(&ctx) == 16);
+
+ /* Now we can set key and IV */
+ EVP_CipherInit_ex(&ctx, NULL, 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 */
+ EVP_CIPHER_CTX_cleanup(&ctx);
+ return 0;
+ }
+ fwrite(outbuf, 1, outlen, out);
+ }
+ if(!EVP_CipherFinal_ex(&ctx, outbuf, &outlen))
+ {
+ /* Error */
+ EVP_CIPHER_CTX_cleanup(&ctx);
+ return 0;
+ }
+ fwrite(outbuf, 1, outlen, out);
+
+ EVP_CIPHER_CTX_cleanup(&ctx);
+ return 1;
+ }
projects / openssl.git / blobdiff