Add OFB block mode to AES-128/192/256
Adds a new configuration of MBEDTLS_CIPHER_MODE_OFB and OFB mode to AES.
diff --git a/include/mbedtls/aes.h b/include/mbedtls/aes.h
index 3c5b133..da22722 100644
--- a/include/mbedtls/aes.h
+++ b/include/mbedtls/aes.h
@@ -291,6 +291,46 @@
unsigned char *output );
#endif /*MBEDTLS_CIPHER_MODE_CFB */
+#if defined(MBEDTLS_CIPHER_MODE_OFB)
+/**
+ * \brief This function performs an AES-OFB (Output Feedback Mode) encryption
+ * or decryption operation.
+ *
+ * For OFB, you must set up the context with mbedtls_aes_setkey_enc(),
+ * regardless of whether you are performing an encryption or decryption
+ * operation. This is because OFB mode uses the same key schedule for
+ * encryption and decryption.
+ *
+ * The OFB operation is identical for encryption or decryption, therefore
+ * no operation mode needs to be specified.
+ *
+ * \note Upon exit, the content of the IV is updated so that you can
+ * call the same function again on the next
+ * block(s) of data and get the same result as if it was
+ * encrypted in one call. This allows a "streaming" usage.
+ * If you need to retain the contents of the
+ * IV, you must either save it manually or use the cipher
+ * module instead.
+ *
+ *
+ * \param ctx The AES context to use for encryption or decryption.
+ * \param length The length of the input data.
+ * \param iv_off The offset in IV (updated after use).
+ * \param iv The initialization vector (updated after use).
+ * \param input The buffer holding the input data.
+ * \param output The buffer holding the output data.
+ *
+ * \return \c 0 on success.
+ */
+int mbedtls_aes_crypt_ofb( mbedtls_aes_context *ctx,
+ size_t length,
+ size_t *iv_off,
+ unsigned char iv[16],
+ const unsigned char *input,
+ unsigned char *output );
+
+#endif /* MBEDTLS_CIPHER_MODE_OFB */
+
#if defined(MBEDTLS_CIPHER_MODE_CTR)
/**
* \brief This function performs an AES-CTR encryption or decryption