+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+
+int main()
+{
+ EVP_CIPHER_CTX ctx;
+ unsigned char key[32] = {0};
+ unsigned char iv[16] = {0};
+ unsigned char in[16] = {0};
+ unsigned char out[32]; /* at least one block longer than in[] */
+ int outlen1, outlen2;
+
+ EVP_EncryptInit(&ctx, EVP_aes_256_cbc(), key, iv);
+ EVP_EncryptUpdate(&ctx, out, &outlen1, in, sizeof(in));
+ EVP_EncryptFinal(&ctx, out + outlen1, &outlen2);
+
+ printf("ciphertext length: %d\n", outlen1 + outlen2);
+
+ return 0;
+}
+
+// result = HMAC(EVP_sha256(), key, 999, data, 888, NULL, NULL);
+// EVP_MD *
+
+// HMAC_CTX hctx;
+// HMAC_CTX_init(&hctx);
+// if (HMAC_Init(&hctx, key, keylen, EVP_sha1())) success;
+// if (HMAC_Update(&hctx, data, datalen)) success;
+// if (HMAC_Final(&hctx, &digest, &digestlen)) success
+// HMAC_CTX_cleanup(&hctx);