mkey/source/ctr.c

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

#include "ctr.h"

void ctr_set_iv( ctr_aes_context* ctx,
                  u8 iv[16] )
{
    memcpy(ctx->iv, iv, 16);
}

void ctr_add_counter( ctr_aes_context* ctx,
                      u32 carry )
{
    u32 counter[4];
    u32 sum;
    int i;

    for(i=0; i<4; i++)
        counter[i] = (ctx->ctr[i*4+0]<<24) | (ctx->ctr[i*4+1]<<16) | (ctx->ctr[i*4+2]<<8) | (ctx->ctr[i*4+3]<<0);

    for(i=3; i>=0; i--)
    {
        sum = counter[i] + carry;

        if (sum < counter[i])
            carry = 1;
        else
            carry = 0;

        counter[i] = sum;
    }

    for(i=0; i<4; i++)
    {
        ctx->ctr[i*4+0] = counter[i]>>24;
        ctx->ctr[i*4+1] = counter[i]>>16;
        ctx->ctr[i*4+2] = counter[i]>>8;
        ctx->ctr[i*4+3] = counter[i]>>0;
    }
}

void ctr_set_counter( ctr_aes_context* ctx,
                      u8 ctr[16] )
{
    memcpy(ctx->ctr, ctr, 16);
}


void ctr_init_counter( ctr_aes_context* ctx,
                       u8 key[16],
                       u8 ctr[16] )
{
    aes_setkey_enc(&ctx->aes, key, 128);
    ctr_set_counter(ctx, ctr);
}


void ctr_crypt_counter_block( ctr_aes_context* ctx,
                              u8 input[16],
                              u8 output[16] )
{
    int i;
    u8 stream[16];


    aes_crypt_ecb(&ctx->aes, AES_ENCRYPT, ctx->ctr, stream);


    if (input)
    {
        for(i=0; i<16; i++)
        {
            output[i] = stream[i] ^ input[i];
        }
    }
    else
    {
        for(i=0; i<16; i++)
            output[i] = stream[i];
    }

    ctr_add_counter(ctx, 1);
}


void ctr_crypt_counter( ctr_aes_context* ctx,
                        u8* input,
                        u8* output,
                        u32 size )
{
    u8 stream[16];
    u32 i;

    while(size >= 16)
    {
        ctr_crypt_counter_block(ctx, input, output);

        if (input)
            input += 16;
        if (output)
            output += 16;

        size -= 16;
    }

    if (size)
    {
        memset(stream, 0, 16);
        ctr_crypt_counter_block(ctx, stream, stream);

        if (input)
        {
            for(i=0; i<size; i++)
                output[i] = input[i] ^ stream[i];
        }
        else
        {
            memcpy(output, stream, size);
        }
    }
}

void ctr_init_cbc_encrypt( ctr_aes_context* ctx,
                           u8 key[16],
                           u8 iv[16] )
{
    aes_setkey_enc(&ctx->aes, key, 128);
    ctr_set_iv(ctx, iv);
}

void ctr_init_cbc_decrypt( ctr_aes_context* ctx,
                           u8 key[16],
                           u8 iv[16] )
{
    aes_setkey_dec(&ctx->aes, key, 128);
    ctr_set_iv(ctx, iv);
}

void ctr_encrypt_cbc( ctr_aes_context* ctx,
                      u8* input,
                      u8* output,
                      u32 size )
{
    aes_crypt_cbc(&ctx->aes, AES_ENCRYPT, size, ctx->iv, input, output);
}

void ctr_decrypt_cbc( ctr_aes_context* ctx,
                      u8* input,
                      u8* output,
                      u32 size )
{
    aes_crypt_cbc(&ctx->aes, AES_DECRYPT, size, ctx->iv, input, output);
}