@CHIP-RTOS C Library - TCP/IP API

Crypt_AES_Decrypt

Decrypt one cipher block of an AES encrypted message.

int Crypt_AES_Decrypt ( const Crypt_AES_Context *aescontext,                         const void far * in,
                        void far * out );

Parameters

aescontext

Pointer to AES context structure (key data)

in

Pointer to 16 bytes (one cipher block) of encrypted input data

out

Pointer to a 16 byte output buffer to receive the recovered "plain text" data. (This may optionally be the same buffer as 'in' references.)

Return Value

0: Success
-1: failed

Comments

The AES (Advanced Encryption Standard) is a block cipher method.   This API decrypts one block of a message.   The cipher block size is 16 bytes.

Prior to calling for the first block of the message, the Crypt_AES_MakeDecryptKey() must be used to initialize the decryption key.

This API may be used repeatedly until your entire message has been recovered.   When your message is not an integral number of 16 byte blocks in length, then you will obtain on the final call the pad bytes that were appended to the original message at the encryption step.

Go here for a summary of cipher method execution times.

See Also

Crypt_AES_MakeEncryptKey        Crypt_AES_MakeDecryptKey        Crypt_AES_Encrypt

RTOS API

This library function invokes a RTOS software interrupt. Refer to this RTOS API function's documentation for more details.

On SC1x3/SC2x (RTOS version >= 1.35, CLIB version >= 2.19) there is also a version of this function available which uses dynamic linking instead of the software interrupt.   This reduces the function's overhead and thus speeds up your application.   This function's name is Crypt_AES_Decrypt_Dyn, however you should not use this function directly.   Instead you should add the define TCPIP_DYN_LINK to your program before including the CLIB's header file(s), as follows:

#define TCPIP_DYN_LINK
#include <clib.h>

This compilation switch will map the original function's name to the dynamic link version.   In this manner, you can easily switch existing programs over to the dynamic link API.

Supported since or modified in @CHIP-RTOS version

SC12	SC13	SC11	SC1x3	SC2x
n/a	n/a	n/a	V1.11	V1.00

Supported by @CHIP-RTOS C Library since version

CLIB
V2.08