diff --git a/isv_app/crypto.cpp b/isv_app/crypto.cpp
new file mode 100644
index 0000000..7f8a99b
--- /dev/null
+++ b/isv_app/crypto.cpp
@@ -0,0 +1,119 @@
+#include <openssl/evp.h> 
+#include <stdint.h>
+#include "crypto.h"
+void handleErrors(){
+    printf("There was a terrible error!\n");
+}
+
+int decrypt(uint8_t *key, uint8_t *ciphertext, int ciphertext_len, uint8_t *plaintext, uint8_t *iv, int iv_len, uint8_t *aad,
+    int aad_len, uint8_t *tag)
+{
+    EVP_CIPHER_CTX *ctx;
+    int len;
+    int plaintext_len;
+    int ret;
+
+    /* Create and initialise the context */
+    if(!(ctx = EVP_CIPHER_CTX_new())) handleErrors();
+
+    /* Initialise the decryption operation. */
+    if(!EVP_DecryptInit_ex(ctx, EVP_aes_128_gcm(), NULL, NULL, NULL))
+        handleErrors();
+
+    /* Set IV length. Not necessary if this is 12 bytes (96 bits) */
+    if(!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, iv_len, NULL))
+        handleErrors();
+
+    /* Initialise key and IV */
+    if(!EVP_DecryptInit_ex(ctx, NULL, NULL, key, iv)) handleErrors();
+    /* Provide any AAD data. This can be called zero or more times as
+     * required
+     */
+    /*if(!EVP_DecryptUpdate(ctx, NULL, &len, aad, aad_len))
+        handleErrors();*/
+
+    /* Provide the message to be decrypted, and obtain the plaintext output.
+     * EVP_DecryptUpdate can be called multiple times if necessary
+     */
+    if(!EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len))
+        handleErrors();
+    plaintext_len = len;
+
+    /* Set expected tag value. Works in OpenSSL 1.0.1d and later */
+    if((tag != NULL) && (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, 16, tag)))
+        handleErrors();
+
+    /* Finalise the decryption. A positive return value indicates success,
+     * anything else is a failure - the plaintext is not trustworthy.
+     */
+    ret = EVP_DecryptFinal_ex(ctx, plaintext + len, &len);
+
+    /* Clean up */
+    EVP_CIPHER_CTX_free(ctx);
+
+    if(ret > 0)
+    {
+        /* Success */
+        plaintext_len += len;
+        return plaintext_len;
+    }
+    else
+    {
+        /* Verify failed */
+        return -1;
+    }
+}
+
+
+int encrypt(uint8_t *key, uint8_t *plaintext, int plaintext_len, uint8_t *ciphertext, uint8_t *iv, int iv_len, uint8_t *aad,
+    int aad_len, uint8_t *tag)
+{
+    EVP_CIPHER_CTX *ctx;
+
+    int len;
+
+    int ciphertext_len;
+
+
+    /* Create and initialise the context */
+    if(!(ctx = EVP_CIPHER_CTX_new())) handleErrors();
+
+    /* Initialise the encryption operation. */
+    if(1 != EVP_EncryptInit_ex(ctx, EVP_aes_128_gcm(), NULL, NULL, NULL))
+        handleErrors();
+
+    /* Set IV length if default 12 bytes (96 bits) is not appropriate */
+    if(1 != EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, iv_len, NULL))
+        handleErrors();
+
+    /* Initialise key and IV */
+    if(1 != EVP_EncryptInit_ex(ctx, NULL, NULL, key, iv)) handleErrors();
+
+    /* Provide any AAD data. This can be called zero or more times as
+     * required
+     */
+/*    if(1 != EVP_EncryptUpdate(ctx, NULL, &len, aad, aad_len))
+        handleErrors();*/
+
+    /* Provide the message to be encrypted, and obtain the encrypted output.
+     * EVP_EncryptUpdate can be called multiple times if necessary
+     */
+    if(1 != EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len))
+        handleErrors();
+    ciphertext_len = len;
+
+    /* Finalise the encryption. Normally ciphertext bytes may be written at
+     * this stage, but this does not occur in GCM mode
+     */
+    if(1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len)) handleErrors();
+    ciphertext_len += len;
+
+    /* Get the tag */
+    if((tag != NULL) && (1 != EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, 16, tag)))
+        handleErrors();
+
+    /* Clean up */
+    EVP_CIPHER_CTX_free(ctx);
+
+    return ciphertext_len;
+}
diff --git a/isv_app/crypto.h b/isv_app/crypto.h
new file mode 100644
index 0000000..f98e243
--- /dev/null
+++ b/isv_app/crypto.h
@@ -0,0 +1,11 @@
+#ifndef CRYPTO_H
+#define CRYPTO_H
+
+int decrypt(uint8_t *key, uint8_t *ciphertext, int ciphertext_len, uint8_t *plaintext, uint8_t *iv, int iv_len, uint8_t *aad,
+    int aad_len, uint8_t *tag);
+
+int encrypt(uint8_t *key, uint8_t *plaintext, int plaintext_len, uint8_t *ciphertext, uint8_t *iv, int iv_len, uint8_t *aad,
+    int aad_len, uint8_t *tag);
+
+void handleErrors();
+#endif /* CRYPTO_H */