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ChaCha20-Lua

Anavrins Dec 24th, 2015 (edited) 393 Never
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  1. -- Chacha20 cipher in ComputerCraft
  2. -- By Anavrins
  3. -- For help and details, you can PM me on the CC forums
  4. -- You may use this code in your projects without asking me, as long as credit is given and this header is kept intact
  5. -- http://www.computercraft.info/forums2/index.php?/user/12870-anavrins
  6. -- http://pastebin.com/GPzf9JSa
  7. -- Last update: June 30, 2019
  8.  
  9. local mod32 = 2^32
  10. local bor = bit32.bor
  11. local bxor = bit32.bxor
  12. local band = bit32.band
  13. local blshift = bit32.lshift
  14. local brshift = bit32.arshift
  15.  
  16. local tau = {("expand 16-byte k"):byte(1,-1)}
  17. local sigma = {("expand 32-byte k"):byte(1,-1)}
  18. local null32 = {("A"):rep(32):byte(1,-1)}
  19. local null12 = {("A"):rep(12):byte(1,-1)}
  20.  
  21. local function rotl(n, b)
  22.     local s = n/(2^(32-b))
  23.     local f = s%1
  24.     return (s-f) + f*mod32
  25. end
  26.  
  27. local function quarterRound(s, a, b, c, d)
  28.     s[a] = (s[a]+s[b])%mod32; s[d] = rotl(bxor(s[d], s[a]), 16)
  29.     s[c] = (s[c]+s[d])%mod32; s[b] = rotl(bxor(s[b], s[c]), 12)
  30.     s[a] = (s[a]+s[b])%mod32; s[d] = rotl(bxor(s[d], s[a]), 8)
  31.     s[c] = (s[c]+s[d])%mod32; s[b] = rotl(bxor(s[b], s[c]), 7)
  32.     return s
  33. end
  34.  
  35. local function hashBlock(state, rnd)
  36.     local s = {unpack(state)}
  37.     for i = 1, rnd do
  38.         local r = i%2==1
  39.         s = r and quarterRound(s, 1, 5,  9, 13) or quarterRound(s, 1, 6, 11, 16)
  40.         s = r and quarterRound(s, 2, 6, 10, 14) or quarterRound(s, 2, 7, 12, 13)
  41.         s = r and quarterRound(s, 3, 7, 11, 15) or quarterRound(s, 3, 8,  9, 14)
  42.         s = r and quarterRound(s, 4, 8, 12, 16) or quarterRound(s, 4, 5, 10, 15)
  43.     end
  44.     for i = 1, 16 do s[i] = (s[i]+state[i])%mod32 end
  45.     return s
  46. end
  47.  
  48. local function LE_toInt(bs, i)
  49.     return (bs[i+1] or 0)+
  50.     blshift((bs[i+2] or 0), 8)+
  51.     blshift((bs[i+3] or 0), 16)+
  52.     blshift((bs[i+4] or 0), 24)
  53. end
  54.  
  55. local function initState(key, nonce, counter)
  56.     local isKey256 = #key == 32
  57.     local const = isKey256 and sigma or tau
  58.     local state = {}
  59.  
  60.     state[ 1] = LE_toInt(const, 0)
  61.     state[ 2] = LE_toInt(const, 4)
  62.     state[ 3] = LE_toInt(const, 8)
  63.     state[ 4] = LE_toInt(const, 12)
  64.  
  65.     state[ 5] = LE_toInt(key, 0)
  66.     state[ 6] = LE_toInt(key, 4)
  67.     state[ 7] = LE_toInt(key, 8)
  68.     state[ 8] = LE_toInt(key, 12)
  69.     state[ 9] = LE_toInt(key, isKey256 and 16 or 0)
  70.     state[10] = LE_toInt(key, isKey256 and 20 or 4)
  71.     state[11] = LE_toInt(key, isKey256 and 24 or 8)
  72.     state[12] = LE_toInt(key, isKey256 and 28 or 12)
  73.  
  74.     state[13] = counter
  75.     state[14] = LE_toInt(nonce, 0)
  76.     state[15] = LE_toInt(nonce, 4)
  77.     state[16] = LE_toInt(nonce, 8)
  78.  
  79.     return state
  80. end
  81.  
  82. local function serialize(state)
  83.     local r = {}
  84.     for i = 1, 16 do
  85.         r[#r+1] = band(state[i], 0xFF)
  86.         r[#r+1] = band(brshift(state[i], 8), 0xFF)
  87.         r[#r+1] = band(brshift(state[i], 16), 0xFF)
  88.         r[#r+1] = band(brshift(state[i], 24), 0xFF)
  89.     end
  90.     return r
  91. end
  92.  
  93. local mt = {
  94.     __tostring = function(a) return string.char(unpack(a)) end,
  95.     __index = {
  96.         toHex = function(self) return ("%02x"):rep(#self):format(unpack(self)) end,
  97.         isEqual = function(self, t)
  98.             if type(t) ~= "table" then return false end
  99.             if #self ~= #t then return false end
  100.             local ret = 0
  101.             for i = 1, #self do
  102.                 ret = bor(ret, bxor(self[i], t[i]))
  103.             end
  104.             return ret == 0
  105.         end
  106.     }
  107. }
  108.  
  109. local function crypt(data, key, nonce, cntr, round)
  110.     assert(type(key) == "table", "ChaCha20: Invalid key format ("..type(key).."), must be table")
  111.     assert(type(nonce) == "table", "ChaCha20: Invalid nonce format ("..type(nonce).."), must be table")
  112.     assert(#key == 16 or #key == 32, "ChaCha20: Invalid key length ("..#key.."), must be 16 or 32")
  113.     assert(#nonce == 12, "ChaCha20: Invalid nonce length ("..#nonce.."), must be 12")
  114.  
  115.     local data = type(data) == "table" and {unpack(data)} or {tostring(data):byte(1,-1)}
  116.     cntr = tonumber(cntr) or 1
  117.     round = tonumber(round) or 20
  118.  
  119.     local out = {}
  120.     local state = initState(key, nonce, cntr)
  121.     local blockAmt = math.floor(#data/64)
  122.     for i = 0, blockAmt do
  123.         local ks = serialize(hashBlock(state, round))
  124.         state[13] = (state[13]+1) % mod32
  125.  
  126.         local block = {}
  127.         for j = 1, 64 do
  128.             block[j] = data[((i)*64)+j]
  129.         end
  130.         for j = 1, #block do
  131.             out[#out+1] = bxor(block[j], ks[j])
  132.         end
  133.  
  134.         if i % 1000 == 0 then
  135.             os.queueEvent("")
  136.             os.pullEvent("")
  137.         end
  138.     end
  139.     return setmetatable(out, mt)
  140. end
  141.  
  142. local function genNonce(len)
  143.     local nonce = {}
  144.     for i = 1, len do
  145.         nonce[i] = math.random(0, 0xFF)
  146.     end
  147.     return setmetatable(nonce, mt)
  148. end
  149.  
  150. local obj = {}
  151. local mtrng = {['__index'] = obj}
  152. local function newRNG(seed)
  153.   local objVars = {}
  154.   objVars.seed = seed
  155.   objVars.cnt = 0
  156.   objVars.block = {}
  157.   return setmetatable(objVars, mtrng)
  158. end
  159.  
  160. -- Specify how many bytes to return
  161. -- 1 Byte is 8 bits, returns int between 0 and 255
  162. -- 2 Bytes is 16 bits, returns int up to 65535
  163. -- 4 Bytes is 32 bits, returns int up to 4294967295
  164. -- Max of 6 Bytes is 48 bits, returns int up to 281474976710655
  165. function obj:nextInt(byte)
  166.   if not byte or byte < 1 or byte > 6 then error("Can only return 1-6 bytes", 2) end
  167.   local output = 0
  168.   for i = 0, byte-1 do
  169.     if #self.block == 0 then
  170.       self.cnt = self.cnt + 1
  171.       self.block = crypt(null32, self.seed, null12, self.cnt)
  172.     end
  173.     local newByte = table.remove(self.block)
  174.     output = output + (newByte * (2^(8*i)))
  175.   end
  176.   return output
  177. end
  178.  
  179. return {
  180.     crypt = crypt,
  181.     genNonce = genNonce,
  182.     newRNG = newRNG
  183. }
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