int do_crypt(char *outfile)

         {

         unsigned char outbuf[];

         int outlen, tmplen;

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

          * another source.

          */

         unsigned char key[] = {,,,,,,,,,,,,,,,};

         unsigned char iv[] = {,,,,,,,};

         char intext[] = "Some Crypto Text";

         EVP_CIPHER_CTX *ctx;

         FILE *out;

         ctx = EVP_CIPHER_CTX_new();

         EVP_EncryptInit_ex(ctx, EVP_idea_cbc(), NULL, key, iv);

         if(!EVP_EncryptUpdate(ctx, outbuf, &outlen, intext, strlen(intext)))

                 {

                 /* Error */

                 return ;

                 }

         /* 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 ;

                 }

         outlen += tmplen;

         EVP_CIPHER_CTX_free(ctx);

         /* Need binary mode for fopen because encrypted data is

          * binary data. Also cannot use strlen() on it because

          * it won't be null terminated and may contain embedded

          * nulls.

          */

         out = fopen(outfile, "wb");

         fwrite(outbuf, , outlen, out);

         fclose(out);

         return ;

         }

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

         {

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

         unsigned char inbuf[], outbuf[ + 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[] = "";

         /* Don't set key or IV right away; we want to check lengths */

         ctx = EVP_CIPHER_CTX_new();

         EVP_CipherInit_ex(&ctx, EVP_aes_128_cbc(), NULL, NULL, NULL,

                 do_encrypt);

         OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == );

         OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == );

         /* Now we can set key and IV */

         EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, do_encrypt);

         for(;;)

                 {

                 inlen = fread(inbuf, , , in);

                 if (inlen <= ) break;

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

                         {

                         /* Error */

                         EVP_CIPHER_CTX_free(ctx);

                         return ;

                         }

                 fwrite(outbuf, , outlen, out);

                 }

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

                 {

                 /* Error */

                 EVP_CIPHER_CTX_free(ctx);

                 return ;

                 }

         fwrite(outbuf, , outlen, out);

         EVP_CIPHER_CTX_free(ctx);

         return ;

         }

// openssl.org/docs/man1.1.0/man3/EVP_EncryptInit_ex.html