File size: 17,825 Bytes
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require("bit");
local gf = require("aeslua.gf");
local util = require("aeslua.util");
--
-- Implementation of AES with nearly pure lua (only bitlib is needed)
--
-- AES with lua is slow, really slow :-)
--
local public = {};
local private = {};
aeslua.aes = public;
-- some constants
public.ROUNDS = "rounds";
public.KEY_TYPE = "type";
public.ENCRYPTION_KEY=1;
public.DECRYPTION_KEY=2;
-- aes SBOX
private.SBox = {};
private.iSBox = {};
-- aes tables
private.table0 = {};
private.table1 = {};
private.table2 = {};
private.table3 = {};
private.tableInv0 = {};
private.tableInv1 = {};
private.tableInv2 = {};
private.tableInv3 = {};
-- round constants
private.rCon = {0x01000000,
0x02000000,
0x04000000,
0x08000000,
0x10000000,
0x20000000,
0x40000000,
0x80000000,
0x1b000000,
0x36000000,
0x6c000000,
0xd8000000,
0xab000000,
0x4d000000,
0x9a000000,
0x2f000000};
--
-- affine transformation for calculating the S-Box of AES
--
function private.affinMap(byte)
mask = 0xf8;
result = 0;
for i = 1,8 do
result = bit.lshift(result,1);
parity = util.byteParity(bit.band(byte,mask));
result = result + parity
-- simulate roll
lastbit = bit.band(mask, 1);
mask = bit.band(bit.rshift(mask, 1),0xff);
if (lastbit ~= 0) then
mask = bit.bor(mask, 0x80);
else
mask = bit.band(mask, 0x7f);
end
end
return bit.bxor(result, 0x63);
end
--
-- calculate S-Box and inverse S-Box of AES
-- apply affine transformation to inverse in finite field 2^8
--
function private.calcSBox()
for i = 0, 255 do
if (i ~= 0) then
inverse = gf.invert(i);
else
inverse = i;
end
mapped = private.affinMap(inverse);
private.SBox[i] = mapped;
private.iSBox[mapped] = i;
end
end
--
-- Calculate round tables
-- round tables are used to calculate shiftRow, MixColumn and SubBytes
-- with 4 table lookups and 4 xor operations.
--
function private.calcRoundTables()
for x = 0,255 do
byte = private.SBox[x];
private.table0[x] = util.putByte(gf.mul(0x03, byte), 0)
+ util.putByte( byte , 1)
+ util.putByte( byte , 2)
+ util.putByte(gf.mul(0x02, byte), 3);
private.table1[x] = util.putByte( byte , 0)
+ util.putByte( byte , 1)
+ util.putByte(gf.mul(0x02, byte), 2)
+ util.putByte(gf.mul(0x03, byte), 3);
private.table2[x] = util.putByte( byte , 0)
+ util.putByte(gf.mul(0x02, byte), 1)
+ util.putByte(gf.mul(0x03, byte), 2)
+ util.putByte( byte , 3);
private.table3[x] = util.putByte(gf.mul(0x02, byte), 0)
+ util.putByte(gf.mul(0x03, byte), 1)
+ util.putByte( byte , 2)
+ util.putByte( byte , 3);
end
end
--
-- Calculate inverse round tables
-- does the inverse of the normal roundtables for the equivalent
-- decryption algorithm.
--
function private.calcInvRoundTables()
for x = 0,255 do
byte = private.iSBox[x];
private.tableInv0[x] = util.putByte(gf.mul(0x0b, byte), 0)
+ util.putByte(gf.mul(0x0d, byte), 1)
+ util.putByte(gf.mul(0x09, byte), 2)
+ util.putByte(gf.mul(0x0e, byte), 3);
private.tableInv1[x] = util.putByte(gf.mul(0x0d, byte), 0)
+ util.putByte(gf.mul(0x09, byte), 1)
+ util.putByte(gf.mul(0x0e, byte), 2)
+ util.putByte(gf.mul(0x0b, byte), 3);
private.tableInv2[x] = util.putByte(gf.mul(0x09, byte), 0)
+ util.putByte(gf.mul(0x0e, byte), 1)
+ util.putByte(gf.mul(0x0b, byte), 2)
+ util.putByte(gf.mul(0x0d, byte), 3);
private.tableInv3[x] = util.putByte(gf.mul(0x0e, byte), 0)
+ util.putByte(gf.mul(0x0b, byte), 1)
+ util.putByte(gf.mul(0x0d, byte), 2)
+ util.putByte(gf.mul(0x09, byte), 3);
end
end
--
-- rotate word: 0xaabbccdd gets 0xbbccddaa
-- used for key schedule
--
function private.rotWord(word)
local tmp = bit.band(word,0xff000000);
return (bit.lshift(word,8) + bit.rshift(tmp,24)) ;
end
--
-- replace all bytes in a word with the SBox.
-- used for key schedule
--
function private.subWord(word)
return util.putByte(private.SBox[util.getByte(word,0)],0)
+ util.putByte(private.SBox[util.getByte(word,1)],1)
+ util.putByte(private.SBox[util.getByte(word,2)],2)
+ util.putByte(private.SBox[util.getByte(word,3)],3);
end
--
-- generate key schedule for aes encryption
--
-- returns table with all round keys and
-- the necessary number of rounds saved in [public.ROUNDS]
--
function public.expandEncryptionKey(key)
local keySchedule = {};
local keyWords = math.floor(#key / 4);
if ((keyWords ~= 4 and keyWords ~= 6 and keyWords ~= 8) or (keyWords * 4 ~= #key)) then
print("Invalid key size: ", keyWords);
return nil;
end
keySchedule[public.ROUNDS] = keyWords + 6;
keySchedule[public.KEY_TYPE] = public.ENCRYPTION_KEY;
for i = 0,keyWords - 1 do
keySchedule[i] = util.putByte(key[i*4+1], 3)
+ util.putByte(key[i*4+2], 2)
+ util.putByte(key[i*4+3], 1)
+ util.putByte(key[i*4+4], 0);
end
for i = keyWords, (keySchedule[public.ROUNDS] + 1)*4 - 1 do
local tmp = keySchedule[i-1];
if ( i % keyWords == 0) then
tmp = private.rotWord(tmp);
tmp = private.subWord(tmp);
local index = math.floor(i/keyWords);
tmp = bit.bxor(tmp,private.rCon[index]);
elseif (keyWords > 6 and i % keyWords == 4) then
tmp = private.subWord(tmp);
end
keySchedule[i] = bit.bxor(keySchedule[(i-keyWords)],tmp);
end
return keySchedule;
end
--
-- Inverse mix column
-- used for key schedule of decryption key
--
function private.invMixColumnOld(word)
local b0 = util.getByte(word,3);
local b1 = util.getByte(word,2);
local b2 = util.getByte(word,1);
local b3 = util.getByte(word,0);
return util.putByte(gf.add(gf.add(gf.add(gf.mul(0x0b, b1),
gf.mul(0x0d, b2)),
gf.mul(0x09, b3)),
gf.mul(0x0e, b0)),3)
+ util.putByte(gf.add(gf.add(gf.add(gf.mul(0x0b, b2),
gf.mul(0x0d, b3)),
gf.mul(0x09, b0)),
gf.mul(0x0e, b1)),2)
+ util.putByte(gf.add(gf.add(gf.add(gf.mul(0x0b, b3),
gf.mul(0x0d, b0)),
gf.mul(0x09, b1)),
gf.mul(0x0e, b2)),1)
+ util.putByte(gf.add(gf.add(gf.add(gf.mul(0x0b, b0),
gf.mul(0x0d, b1)),
gf.mul(0x09, b2)),
gf.mul(0x0e, b3)),0);
end
--
-- Optimized inverse mix column
-- look at http://fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.311.pdf
-- TODO: make it work
--
function private.invMixColumn(word)
local b0 = util.getByte(word,3);
local b1 = util.getByte(word,2);
local b2 = util.getByte(word,1);
local b3 = util.getByte(word,0);
local t = bit.bxor(b3,b2);
local u = bit.bxor(b1,b0);
local v = bit.bxor(t,u);
v = bit.bxor(v,gf.mul(0x08,v));
w = bit.bxor(v,gf.mul(0x04, bit.bxor(b2,b0)));
v = bit.bxor(v,gf.mul(0x04, bit.bxor(b3,b1)));
return util.putByte( bit.bxor(bit.bxor(b3,v), gf.mul(0x02, bit.bxor(b0,b3))), 0)
+ util.putByte( bit.bxor(bit.bxor(b2,w), gf.mul(0x02, t )), 1)
+ util.putByte( bit.bxor(bit.bxor(b1,v), gf.mul(0x02, bit.bxor(b0,b3))), 2)
+ util.putByte( bit.bxor(bit.bxor(b0,w), gf.mul(0x02, u )), 3);
end
--
-- generate key schedule for aes decryption
--
-- uses key schedule for aes encryption and transforms each
-- key by inverse mix column.
--
function public.expandDecryptionKey(key)
local keySchedule = public.expandEncryptionKey(key);
if (keySchedule == nil) then
return nil;
end
keySchedule[public.KEY_TYPE] = public.DECRYPTION_KEY;
for i = 4, (keySchedule[public.ROUNDS] + 1)*4 - 5 do
keySchedule[i] = private.invMixColumnOld(keySchedule[i]);
end
return keySchedule;
end
--
-- xor round key to state
--
function private.addRoundKey(state, key, round)
for i = 0, 3 do
state[i] = bit.bxor(state[i], key[round*4+i]);
end
end
--
-- do encryption round (ShiftRow, SubBytes, MixColumn together)
--
function private.doRound(origState, dstState)
dstState[0] = bit.bxor(bit.bxor(bit.bxor(
private.table0[util.getByte(origState[0],3)],
private.table1[util.getByte(origState[1],2)]),
private.table2[util.getByte(origState[2],1)]),
private.table3[util.getByte(origState[3],0)]);
dstState[1] = bit.bxor(bit.bxor(bit.bxor(
private.table0[util.getByte(origState[1],3)],
private.table1[util.getByte(origState[2],2)]),
private.table2[util.getByte(origState[3],1)]),
private.table3[util.getByte(origState[0],0)]);
dstState[2] = bit.bxor(bit.bxor(bit.bxor(
private.table0[util.getByte(origState[2],3)],
private.table1[util.getByte(origState[3],2)]),
private.table2[util.getByte(origState[0],1)]),
private.table3[util.getByte(origState[1],0)]);
dstState[3] = bit.bxor(bit.bxor(bit.bxor(
private.table0[util.getByte(origState[3],3)],
private.table1[util.getByte(origState[0],2)]),
private.table2[util.getByte(origState[1],1)]),
private.table3[util.getByte(origState[2],0)]);
end
--
-- do last encryption round (ShiftRow and SubBytes)
--
function private.doLastRound(origState, dstState)
dstState[0] = util.putByte(private.SBox[util.getByte(origState[0],3)], 3)
+ util.putByte(private.SBox[util.getByte(origState[1],2)], 2)
+ util.putByte(private.SBox[util.getByte(origState[2],1)], 1)
+ util.putByte(private.SBox[util.getByte(origState[3],0)], 0);
dstState[1] = util.putByte(private.SBox[util.getByte(origState[1],3)], 3)
+ util.putByte(private.SBox[util.getByte(origState[2],2)], 2)
+ util.putByte(private.SBox[util.getByte(origState[3],1)], 1)
+ util.putByte(private.SBox[util.getByte(origState[0],0)], 0);
dstState[2] = util.putByte(private.SBox[util.getByte(origState[2],3)], 3)
+ util.putByte(private.SBox[util.getByte(origState[3],2)], 2)
+ util.putByte(private.SBox[util.getByte(origState[0],1)], 1)
+ util.putByte(private.SBox[util.getByte(origState[1],0)], 0);
dstState[3] = util.putByte(private.SBox[util.getByte(origState[3],3)], 3)
+ util.putByte(private.SBox[util.getByte(origState[0],2)], 2)
+ util.putByte(private.SBox[util.getByte(origState[1],1)], 1)
+ util.putByte(private.SBox[util.getByte(origState[2],0)], 0);
end
--
-- do decryption round
--
function private.doInvRound(origState, dstState)
dstState[0] = bit.bxor(bit.bxor(bit.bxor(
private.tableInv0[util.getByte(origState[0],3)],
private.tableInv1[util.getByte(origState[3],2)]),
private.tableInv2[util.getByte(origState[2],1)]),
private.tableInv3[util.getByte(origState[1],0)]);
dstState[1] = bit.bxor(bit.bxor(bit.bxor(
private.tableInv0[util.getByte(origState[1],3)],
private.tableInv1[util.getByte(origState[0],2)]),
private.tableInv2[util.getByte(origState[3],1)]),
private.tableInv3[util.getByte(origState[2],0)]);
dstState[2] = bit.bxor(bit.bxor(bit.bxor(
private.tableInv0[util.getByte(origState[2],3)],
private.tableInv1[util.getByte(origState[1],2)]),
private.tableInv2[util.getByte(origState[0],1)]),
private.tableInv3[util.getByte(origState[3],0)]);
dstState[3] = bit.bxor(bit.bxor(bit.bxor(
private.tableInv0[util.getByte(origState[3],3)],
private.tableInv1[util.getByte(origState[2],2)]),
private.tableInv2[util.getByte(origState[1],1)]),
private.tableInv3[util.getByte(origState[0],0)]);
end
--
-- do last decryption round
--
function private.doInvLastRound(origState, dstState)
dstState[0] = util.putByte(private.iSBox[util.getByte(origState[0],3)], 3)
+ util.putByte(private.iSBox[util.getByte(origState[3],2)], 2)
+ util.putByte(private.iSBox[util.getByte(origState[2],1)], 1)
+ util.putByte(private.iSBox[util.getByte(origState[1],0)], 0);
dstState[1] = util.putByte(private.iSBox[util.getByte(origState[1],3)], 3)
+ util.putByte(private.iSBox[util.getByte(origState[0],2)], 2)
+ util.putByte(private.iSBox[util.getByte(origState[3],1)], 1)
+ util.putByte(private.iSBox[util.getByte(origState[2],0)], 0);
dstState[2] = util.putByte(private.iSBox[util.getByte(origState[2],3)], 3)
+ util.putByte(private.iSBox[util.getByte(origState[1],2)], 2)
+ util.putByte(private.iSBox[util.getByte(origState[0],1)], 1)
+ util.putByte(private.iSBox[util.getByte(origState[3],0)], 0);
dstState[3] = util.putByte(private.iSBox[util.getByte(origState[3],3)], 3)
+ util.putByte(private.iSBox[util.getByte(origState[2],2)], 2)
+ util.putByte(private.iSBox[util.getByte(origState[1],1)], 1)
+ util.putByte(private.iSBox[util.getByte(origState[0],0)], 0);
end
--
-- encrypts 16 Bytes
-- key encryption key schedule
-- input array with input data
-- inputOffset start index for input
-- output array for encrypted data
-- outputOffset start index for output
--
function public.encrypt(key, input, inputOffset, output, outputOffset)
--default parameters
inputOffset = inputOffset or 1;
output = output or {};
outputOffset = outputOffset or 1;
local state = {};
local tmpState = {};
if (key[public.KEY_TYPE] ~= public.ENCRYPTION_KEY) then
print("No encryption key: ", key[public.KEY_TYPE]);
return;
end
state = util.bytesToInts(input, inputOffset, 4);
private.addRoundKey(state, key, 0);
local round = 1;
while (round < key[public.ROUNDS] - 1) do
-- do a double round to save temporary assignments
private.doRound(state, tmpState);
private.addRoundKey(tmpState, key, round);
round = round + 1;
private.doRound(tmpState, state);
private.addRoundKey(state, key, round);
round = round + 1;
end
private.doRound(state, tmpState);
private.addRoundKey(tmpState, key, round);
round = round +1;
private.doLastRound(tmpState, state);
private.addRoundKey(state, key, round);
return util.intsToBytes(state, output, outputOffset);
end
--
-- decrypt 16 bytes
-- key decryption key schedule
-- input array with input data
-- inputOffset start index for input
-- output array for decrypted data
-- outputOffset start index for output
---
function public.decrypt(key, input, inputOffset, output, outputOffset)
-- default arguments
inputOffset = inputOffset or 1;
output = output or {};
outputOffset = outputOffset or 1;
local state = {};
local tmpState = {};
if (key[public.KEY_TYPE] ~= public.DECRYPTION_KEY) then
print("No decryption key: ", key[public.KEY_TYPE]);
return;
end
state = util.bytesToInts(input, inputOffset, 4);
private.addRoundKey(state, key, key[public.ROUNDS]);
local round = key[public.ROUNDS] - 1;
while (round > 2) do
-- do a double round to save temporary assignments
private.doInvRound(state, tmpState);
private.addRoundKey(tmpState, key, round);
round = round - 1;
private.doInvRound(tmpState, state);
private.addRoundKey(state, key, round);
round = round - 1;
end
private.doInvRound(state, tmpState);
private.addRoundKey(tmpState, key, round);
round = round - 1;
private.doInvLastRound(tmpState, state);
private.addRoundKey(state, key, round);
return util.intsToBytes(state, output, outputOffset);
end
-- calculate all tables when loading this file
private.calcSBox();
private.calcRoundTables();
private.calcInvRoundTables();
return public; |