lib/crypt/lib_crypt.c

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/* Copyright (c) 2009 Nordic Semiconductor. All Rights Reserved.
 *
 * The information contained herein is confidential property of Nordic 
 * Semiconductor ASA.Terms and conditions of usage are described in detail 
 * in NORDIC SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT. 
 *
 * Licensees are granted free, non-transferable use of the information. NO
 * WARRENTY of ANY KIND is provided. This heading must NOT be removed from
 * the file.
 *              
 * $LastChangedRevision: 133 $
 */

#include "lib_crypt.h"
#include "hal_aes.h"
#include "memdefs.h"

static uint8_t aes_counter[16];

void lib_crypt_init(uint8_t * key, const uint8_t * init_counter)
{
    hal_aes_setup(false, ECB, key, NULL);

    if(init_counter)
    {
        lib_crypt_set_counter(init_counter);
    }
}

void lib_crypt_set_counter(const uint8_t * counter)
{
    uint8_t i;
    for(i=0;i<16;i++)
    {
        aes_counter[i] = counter[i];
    }
}

void lib_crypt(uint8_t * dest_buf, const uint8_t * src_buf, uint8_t length,const uint8_t * ls5b_value)
{
    uint8_t i;
  uint8_t encr_buffer[16];   //AES buffer. Needed to do XOR

  //Set LS5B
    for(i=0;i<5;i++)
    {
        aes_counter[i] = ls5b_value[i];
    }   

  //Run AES with aes_counter
    hal_aes_crypt(encr_buffer,aes_counter);
    
  //Encrypt data, based on XOR operation in AES counter mode.
    for(i=0;i<length; i++)
    {
        dest_buf[i] = src_buf[i] ^ encr_buffer[i];
    }
}