The ISAAC cipher: Difference between revisions

</pre>

=={{header|Lua}}==

<lang lua>

#!/usr/bin/env lua

-- ISAAC - Lua 5.3

-- External Results

local randRsl = {};

local randCnt = 0;

-- Internal State

local mm = {};

local aa,bb,cc = 0,0,0;

-- Cap to maintain 32 bit maths

local cap = 0x100000000;

-- CipherMode

local ENCRYPT = 1;

local DECRYPT = 2;

function isaac()

cc = ( cc + 1 ) % cap; -- cc just gets incremented once per 256 results

bb = ( bb + cc ) % cap; -- then combined with bb

for i = 0,255 do

local x = mm[i];

local y;

local imod = i % 4;

if imod == 0 then aa = aa ~ (aa << 13);

elseif imod == 1 then aa = aa ~ (aa >> 6);

elseif imod == 2 then aa = aa ~ (aa << 2);

elseif imod == 3 then aa = aa ~ (aa >> 16);

end

aa = ( mm[(i+128)%256] + aa ) % cap;

y = ( mm[(x>>2) % 256] + aa + bb ) % cap;

mm[i] = y;

bb = ( mm[(y>>10)%256] + x ) % cap;

randRsl[i] = bb;

end

randCnt = 0; -- Prepare to use the first set of results.

end

function mix(a)

a[0] = ( a[0] ~ ( a[1] << 11 ) ) % cap; a[3] = ( a[3] + a[0] ) % cap; a[1] = ( a[1] + a[2] ) % cap;

a[1] = ( a[1] ~ ( a[2] >> 2 ) ) % cap; a[4] = ( a[4] + a[1] ) % cap; a[2] = ( a[2] + a[3] ) % cap;

a[2] = ( a[2] ~ ( a[3] << 8 ) ) % cap; a[5] = ( a[5] + a[2] ) % cap; a[3] = ( a[3] + a[4] ) % cap;

a[3] = ( a[3] ~ ( a[4] >> 16 ) ) % cap; a[6] = ( a[6] + a[3] ) % cap; a[4] = ( a[4] + a[5] ) % cap;

a[4] = ( a[4] ~ ( a[5] << 10 ) ) % cap; a[7] = ( a[7] + a[4] ) % cap; a[5] = ( a[5] + a[6] ) % cap;

a[5] = ( a[5] ~ ( a[6] >> 4 ) ) % cap; a[0] = ( a[0] + a[5] ) % cap; a[6] = ( a[6] + a[7] ) % cap;

a[6] = ( a[6] ~ ( a[7] << 8 ) ) % cap; a[1] = ( a[1] + a[6] ) % cap; a[7] = ( a[7] + a[0] ) % cap;

a[7] = ( a[7] ~ ( a[0] >> 9 ) ) % cap; a[2] = ( a[2] + a[7] ) % cap; a[0] = ( a[0] + a[1] ) % cap;

end

function randInit(flag)

-- The golden ratio in 32 bit

-- math.floor((((math.sqrt(5)+1)/2)%1)*2^32) == 2654435769 == 0x9e3779b9

local a = { [0] = 0x9e3779b9, 0x9e3779b9, 0x9e3779b9, 0x9e3779b9, 0x9e3779b9, 0x9e3779b9, 0x9e3779b9, 0x9e3779b9, };

aa,bb,cc = 0,0,0;

for i = 1,4 do mix(a) end -- Scramble it.

for i = 0,255,8 do -- Fill in mm[] with messy stuff.

if flag then -- Use all the information in the seed.

for j = 0,7 do

a[j] = ( a[j] + randRsl[i+j] ) % cap;

end

end

mix(a);

for j = 0,7 do

mm[i+j] = a[j];

end

end

if flag then

-- Do a second pass to make all of the seed affect all of mm.

for i = 0,255,8 do

for j = 0,7 do

a[j] = ( a[j] + mm[i+j] ) % cap;

end

mix(a);

for j = 0,7 do

mm[i+j] = a[j];

end

end

end

isaac(); -- Fill in the first set of results.

randCnt = 0; -- Prepare to use the first set of results.

end

-- Seed ISAAC with a given string.

-- The string can be any size. The first 256 values will be used.

function seedIsaac(seed,flag)

local seedLength = #seed;

for i = 0,255 do mm[i] = 0; end

for i = 0,255 do randRsl[i] = seed:byte(i+1,i+1) or 0; end

randInit(flag);

end

-- Get a random 32-bit value 0..MAXINT

function getRandom32Bit()

local result = randRsl[randCnt];

randCnt = randCnt + 1;

if randCnt > 255 then

isaac();

randCnt = 0;

end

return result;

end

-- Get a random character in printable ASCII range

function getRandomChar()

return getRandom32Bit() % 95 + 32;

end

-- Convert an ASCII string to a hexadecimal string.

function ascii2hex(source)

local ss = "";

for i = 1,#source do

ss = ss..string.format("%02X",source:byte(i,i));

end

return ss

end

-- XOR encrypt on random stream.

function vernam(msg)

local msgLength = #msg;

local destination = {};

for i = 1, msgLength do

destination[i] = string.char(getRandomChar() ~ msg:byte(i,i));

end

return table.concat(destination);

end

-- Caesar-shift a character <shift> places: Generalized Vigenere

function caesar(m, ch, shift, modulo, start)

local n

local si = 1

if m == DECRYPT then shift = shift*-1 ; end

n = (ch - start) + shift;

if n < 0 then si,n = -1,n*-1 ; end

n = ( n % modulo ) * si;

if n < 0 then n = n + modulo ; end

return start + n;

end

-- Vigenere mod 95 encryption & decryption.

function vigenere(msg,m)

local msgLength = #msg;

local destination = {};

for i = 1,msgLength do

destination[i] = string.char( caesar(m, msg:byte(i,i), getRandomChar(), 95, 32) );

end

return table.concat(destination);

end

function main(noprint)

local msg = "a Top Secret secret";

local key = "this is my secret key";

local xorCipherText, modCipherText, xorPlainText, modPlainText;

-- (1) Seed ISAAC with the key

seedIsaac(key, true);

-- (2) Encryption

-- (a) XOR (Vernam)

xorCipherText = vernam(msg);

-- (b) MOD (Vigenere)

modCipherText = vigenere(msg, ENCRYPT);

-- (3) Decryption

seedIsaac(key, true);

-- (a) XOR (Vernam)

xorPlainText = vernam(xorCipherText);

-- (b) MOD (Vigenere)

modPlainText = vigenere(modCipherText, DECRYPT);

-- Program output

if not noprint then

print("Message: " .. msg);

print("Key : " .. key);

print("XOR : " .. ascii2hex(xorCipherText));

print("XOR dcr: " .. xorPlainText);

print("MOD : " .. ascii2hex(modCipherText));

print("MOD dcr: " .. modPlainText);

end

end

</lang>

{{out}}

<pre>

Message: a Top Secret secret

Key : this is my secret key

XOR : 1c0636190b1260233b35125f1e1d0e2f4c5422

MOD : 734270227d36772a783b4f2a5f206266236978

XOR dcr: a Top Secret secret

MOD dcr: a Top Secret secret