1214501Srpaulo/* 2214501Srpaulo * AES (Rijndael) cipher - decrypt 3214501Srpaulo * 4214501Srpaulo * Modifications to public domain implementation: 5214501Srpaulo * - support only 128-bit keys 6214501Srpaulo * - cleanup 7214501Srpaulo * - use C pre-processor to make it easier to change S table access 8214501Srpaulo * - added option (AES_SMALL_TABLES) for reducing code size by about 8 kB at 9214501Srpaulo * cost of reduced throughput (quite small difference on Pentium 4, 10214501Srpaulo * 10-25% when using -O1 or -O2 optimization) 11214501Srpaulo * 12214501Srpaulo * Copyright (c) 2003-2005, Jouni Malinen <j@w1.fi> 13214501Srpaulo * 14214501Srpaulo * This program is free software; you can redistribute it and/or modify 15214501Srpaulo * it under the terms of the GNU General Public License version 2 as 16214501Srpaulo * published by the Free Software Foundation. 17214501Srpaulo * 18214501Srpaulo * Alternatively, this software may be distributed under the terms of BSD 19214501Srpaulo * license. 20214501Srpaulo * 21214501Srpaulo * See README and COPYING for more details. 22214501Srpaulo */ 23214501Srpaulo 24214501Srpaulo#include "includes.h" 25214501Srpaulo 26214501Srpaulo#include "common.h" 27214501Srpaulo#include "crypto.h" 28214501Srpaulo#include "aes_i.h" 29214501Srpaulo 30214501Srpaulo/** 31214501Srpaulo * Expand the cipher key into the decryption key schedule. 32214501Srpaulo * 33214501Srpaulo * @return the number of rounds for the given cipher key size. 34214501Srpaulo */ 35214501Srpaulovoid rijndaelKeySetupDec(u32 rk[/*44*/], const u8 cipherKey[]) 36214501Srpaulo{ 37214501Srpaulo int Nr = 10, i, j; 38214501Srpaulo u32 temp; 39214501Srpaulo 40214501Srpaulo /* expand the cipher key: */ 41214501Srpaulo rijndaelKeySetupEnc(rk, cipherKey); 42214501Srpaulo /* invert the order of the round keys: */ 43214501Srpaulo for (i = 0, j = 4*Nr; i < j; i += 4, j -= 4) { 44214501Srpaulo temp = rk[i ]; rk[i ] = rk[j ]; rk[j ] = temp; 45214501Srpaulo temp = rk[i + 1]; rk[i + 1] = rk[j + 1]; rk[j + 1] = temp; 46214501Srpaulo temp = rk[i + 2]; rk[i + 2] = rk[j + 2]; rk[j + 2] = temp; 47214501Srpaulo temp = rk[i + 3]; rk[i + 3] = rk[j + 3]; rk[j + 3] = temp; 48214501Srpaulo } 49214501Srpaulo /* apply the inverse MixColumn transform to all round keys but the 50214501Srpaulo * first and the last: */ 51214501Srpaulo for (i = 1; i < Nr; i++) { 52214501Srpaulo rk += 4; 53214501Srpaulo for (j = 0; j < 4; j++) { 54214501Srpaulo rk[j] = TD0_(TE4((rk[j] >> 24) )) ^ 55214501Srpaulo TD1_(TE4((rk[j] >> 16) & 0xff)) ^ 56214501Srpaulo TD2_(TE4((rk[j] >> 8) & 0xff)) ^ 57214501Srpaulo TD3_(TE4((rk[j] ) & 0xff)); 58214501Srpaulo } 59214501Srpaulo } 60214501Srpaulo} 61214501Srpaulo 62214501Srpaulovoid * aes_decrypt_init(const u8 *key, size_t len) 63214501Srpaulo{ 64214501Srpaulo u32 *rk; 65214501Srpaulo if (len != 16) 66214501Srpaulo return NULL; 67214501Srpaulo rk = os_malloc(AES_PRIV_SIZE); 68214501Srpaulo if (rk == NULL) 69214501Srpaulo return NULL; 70214501Srpaulo rijndaelKeySetupDec(rk, key); 71214501Srpaulo return rk; 72214501Srpaulo} 73214501Srpaulo 74214501Srpaulostatic void rijndaelDecrypt(const u32 rk[/*44*/], const u8 ct[16], u8 pt[16]) 75214501Srpaulo{ 76214501Srpaulo u32 s0, s1, s2, s3, t0, t1, t2, t3; 77214501Srpaulo const int Nr = 10; 78214501Srpaulo#ifndef FULL_UNROLL 79214501Srpaulo int r; 80214501Srpaulo#endif /* ?FULL_UNROLL */ 81214501Srpaulo 82214501Srpaulo /* 83214501Srpaulo * map byte array block to cipher state 84214501Srpaulo * and add initial round key: 85214501Srpaulo */ 86214501Srpaulo s0 = GETU32(ct ) ^ rk[0]; 87214501Srpaulo s1 = GETU32(ct + 4) ^ rk[1]; 88214501Srpaulo s2 = GETU32(ct + 8) ^ rk[2]; 89214501Srpaulo s3 = GETU32(ct + 12) ^ rk[3]; 90214501Srpaulo 91214501Srpaulo#define ROUND(i,d,s) \ 92214501Srpaulod##0 = TD0(s##0) ^ TD1(s##3) ^ TD2(s##2) ^ TD3(s##1) ^ rk[4 * i]; \ 93214501Srpaulod##1 = TD0(s##1) ^ TD1(s##0) ^ TD2(s##3) ^ TD3(s##2) ^ rk[4 * i + 1]; \ 94214501Srpaulod##2 = TD0(s##2) ^ TD1(s##1) ^ TD2(s##0) ^ TD3(s##3) ^ rk[4 * i + 2]; \ 95214501Srpaulod##3 = TD0(s##3) ^ TD1(s##2) ^ TD2(s##1) ^ TD3(s##0) ^ rk[4 * i + 3] 96214501Srpaulo 97214501Srpaulo#ifdef FULL_UNROLL 98214501Srpaulo 99214501Srpaulo ROUND(1,t,s); 100214501Srpaulo ROUND(2,s,t); 101214501Srpaulo ROUND(3,t,s); 102214501Srpaulo ROUND(4,s,t); 103214501Srpaulo ROUND(5,t,s); 104214501Srpaulo ROUND(6,s,t); 105214501Srpaulo ROUND(7,t,s); 106214501Srpaulo ROUND(8,s,t); 107214501Srpaulo ROUND(9,t,s); 108214501Srpaulo 109214501Srpaulo rk += Nr << 2; 110214501Srpaulo 111214501Srpaulo#else /* !FULL_UNROLL */ 112214501Srpaulo 113214501Srpaulo /* Nr - 1 full rounds: */ 114214501Srpaulo r = Nr >> 1; 115214501Srpaulo for (;;) { 116214501Srpaulo ROUND(1,t,s); 117214501Srpaulo rk += 8; 118214501Srpaulo if (--r == 0) 119214501Srpaulo break; 120214501Srpaulo ROUND(0,s,t); 121214501Srpaulo } 122214501Srpaulo 123214501Srpaulo#endif /* ?FULL_UNROLL */ 124214501Srpaulo 125214501Srpaulo#undef ROUND 126214501Srpaulo 127214501Srpaulo /* 128214501Srpaulo * apply last round and 129214501Srpaulo * map cipher state to byte array block: 130214501Srpaulo */ 131214501Srpaulo s0 = TD41(t0) ^ TD42(t3) ^ TD43(t2) ^ TD44(t1) ^ rk[0]; 132214501Srpaulo PUTU32(pt , s0); 133214501Srpaulo s1 = TD41(t1) ^ TD42(t0) ^ TD43(t3) ^ TD44(t2) ^ rk[1]; 134214501Srpaulo PUTU32(pt + 4, s1); 135214501Srpaulo s2 = TD41(t2) ^ TD42(t1) ^ TD43(t0) ^ TD44(t3) ^ rk[2]; 136214501Srpaulo PUTU32(pt + 8, s2); 137214501Srpaulo s3 = TD41(t3) ^ TD42(t2) ^ TD43(t1) ^ TD44(t0) ^ rk[3]; 138214501Srpaulo PUTU32(pt + 12, s3); 139214501Srpaulo} 140214501Srpaulo 141214501Srpaulovoid aes_decrypt(void *ctx, const u8 *crypt, u8 *plain) 142214501Srpaulo{ 143214501Srpaulo rijndaelDecrypt(ctx, crypt, plain); 144214501Srpaulo} 145214501Srpaulo 146214501Srpaulo 147214501Srpaulovoid aes_decrypt_deinit(void *ctx) 148214501Srpaulo{ 149214501Srpaulo os_memset(ctx, 0, AES_PRIV_SIZE); 150214501Srpaulo os_free(ctx); 151214501Srpaulo} 152