Click here to Skip to main content
12,395,871 members (62,424 online)
Rate this:
 
Please Sign up or sign in to vote.
See more: C++
Recently I have a task for a AES algorithm, the key length is 256bits, the buffer length is asked for 256bits. But the normal AES algorithm is 128bits for the plain text.
how to encrypt the 256bits plain text like this:
void rijndaelDecrypt(const u32 *rk, int nrounds, const u8 ciphertext[32],u8 plaintext[32])
{
  u32 s0, s1, s2, s3, t0, t1, t2, t3;
  #ifndef FULL_UNROLL
    int r;
  #endif /* ?FULL_UNROLL */

  /*
  * map byte array block to cipher state
  * and add initial round key:
  */
    s0 = GETU32(ciphertext     ) ^ rk[0];
    s1 = GETU32(ciphertext +  4) ^ rk[1];
    s2 = GETU32(ciphertext +  8) ^ rk[2];
    s3 = GETU32(ciphertext + 12) ^ rk[3];
  #ifdef FULL_UNROLL
    /* round 1: */
    t0 = Td0[s0 >> 24] ^ Td1[(s3 >> 16) & 0xff] ^ Td2[(s2 >>  8) & 0xff] ^ Td3[s1 & 0xff] ^ rk[ 4];
    t1 = Td0[s1 >> 24] ^ Td1[(s0 >> 16) & 0xff] ^ Td2[(s3 >>  8) & 0xff] ^ Td3[s2 & 0xff] ^ rk[ 5];
    t2 = Td0[s2 >> 24] ^ Td1[(s1 >> 16) & 0xff] ^ Td2[(s0 >>  8) & 0xff] ^ Td3[s3 & 0xff] ^ rk[ 6];
    t3 = Td0[s3 >> 24] ^ Td1[(s2 >> 16) & 0xff] ^ Td2[(s1 >>  8) & 0xff] ^ Td3[s0 & 0xff] ^ rk[ 7];
    /* round 2: */
    s0 = Td0[t0 >> 24] ^ Td1[(t3 >> 16) & 0xff] ^ Td2[(t2 >>  8) & 0xff] ^ Td3[t1 & 0xff] ^ rk[ 8];
    s1 = Td0[t1 >> 24] ^ Td1[(t0 >> 16) & 0xff] ^ Td2[(t3 >>  8) & 0xff] ^ Td3[t2 & 0xff] ^ rk[ 9];
    s2 = Td0[t2 >> 24] ^ Td1[(t1 >> 16) & 0xff] ^ Td2[(t0 >>  8) & 0xff] ^ Td3[t3 & 0xff] ^ rk[10];
    s3 = Td0[t3 >> 24] ^ Td1[(t2 >> 16) & 0xff] ^ Td2[(t1 >>  8) & 0xff] ^ Td3[t0 & 0xff] ^ rk[11];
    /* round 3: */
    t0 = Td0[s0 >> 24] ^ Td1[(s3 >> 16) & 0xff] ^ Td2[(s2 >>  8) & 0xff] ^ Td3[s1 & 0xff] ^ rk[12];
    t1 = Td0[s1 >> 24] ^ Td1[(s0 >> 16) & 0xff] ^ Td2[(s3 >>  8) & 0xff] ^ Td3[s2 & 0xff] ^ rk[13];
    t2 = Td0[s2 >> 24] ^ Td1[(s1 >> 16) & 0xff] ^ Td2[(s0 >>  8) & 0xff] ^ Td3[s3 & 0xff] ^ rk[14];
    t3 = Td0[s3 >> 24] ^ Td1[(s2 >> 16) & 0xff] ^ Td2[(s1 >>  8) & 0xff] ^ Td3[s0 & 0xff] ^ rk[15];
How to change the code?

Master,please give me help
Posted 29-Nov-12 1:08am
Updated 29-Nov-12 1:11am
v2

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

  Print Answers RSS
Top Experts
Last 24hrsThis month


Advertise | Privacy | Mobile
Web02 | 2.8.160721.1 | Last Updated 29 Nov 2012
Copyright © CodeProject, 1999-2016
All Rights Reserved. Terms of Service
Layout: fixed | fluid

CodeProject, 503-250 Ferrand Drive Toronto Ontario, M3C 3G8 Canada +1 416-849-8900 x 100