Password Based Encrypt / Decrypt Script

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Jor'Mox
Posts: 1099
Joined: Wed Apr 03, 2013 2:19 am

Password Based Encrypt / Decrypt Script

Post by Jor'Mox » Sat Sep 21, 2013 7:25 pm

So, I posted this elsewhere, and figured I would put a copy here in case someone wanted it. Most of the work ISN'T mine. It is all accessed via encrypt_msg(msg, password) and decrypt_msg(msg, password). It works by generating a hash from the password (which is all done via someone else's code), and then shifting the char values of each character of the message by the corresponding char value in the hash (the hash is repeated for long messages). It isn't necessarily the most secure encryption available, but it should generally be more than enough to keep the average person from accessing the encrypted data without the correct password.
Code: [show] | [select all] lua
--  
--  Adaptation of the Secure Hashing Algorithm (SHA-244/256)
--  Found Here: http://lua-users.org/wiki/SecureHashAlgorithm
--  
--  Using an adapted version of the bit library
--  Found Here: https://bitbucket.org/Boolsheet/bslf/src/1ee664885805/bit.lua
--  
 
local MOD = 2^32
local MODM = MOD-1
 
local function memoize(f)
	local mt = {}
	local t = setmetatable({}, mt)
	function mt:__index(k)
		local v = f(k)
		t[k] = v
		return v
	end
	return t
end
 
local function make_bitop_uncached(t, m)
	local function bitop(a, b)
		local res,p = 0,1
		while a ~= 0 and b ~= 0 do
			local am, bm = a % m, b % m
			res = res + t[am][bm] * p
			a = (a - am) / m
			b = (b - bm) / m
			p = p*m
		end
		res = res + (a + b) * p
		return res
	end
	return bitop
end
 
local function make_bitop(t)
	local op1 = make_bitop_uncached(t,2^1)
	local op2 = memoize(function(a) return memoize(function(b) return op1(a, b) end) end)
	return make_bitop_uncached(op2, 2 ^ (t.n or 1))
end
 
local bxor1 = make_bitop({[0] = {[0] = 0,[1] = 1}, [1] = {[0] = 1, [1] = 0}, n = 4})
 
local function bxor(a, b, c, ...)
	local z = nil
	if b then
		a = a % MOD
		b = b % MOD
		z = bxor1(a, b)
		if c then z = bxor(z, c, ...) end
		return z
	elseif a then return a % MOD
	else return 0 end
end
 
local function band(a, b, c, ...)
	local z
	if b then
		a = a % MOD
		b = b % MOD
		z = ((a + b) - bxor1(a,b)) / 2
		if c then z = bit32_band(z, c, ...) end
		return z
	elseif a then return a % MOD
	else return MODM end
end
 
local function bnot(x) return (-1 - x) % MOD end
 
local function rshift1(a, disp)
	if disp < 0 then return lshift(a,-disp) end
	return math.floor(a % 2 ^ 32 / 2 ^ disp)
end
 
local function rshift(x, disp)
	if disp > 31 or disp < -31 then return 0 end
	return rshift1(x % MOD, disp)
end
 
local function lshift(a, disp)
	if disp < 0 then return rshift(a,-disp) end
	return (a * 2 ^ disp) % 2 ^ 32
end
 
local function rrotate(x, disp)
	x = x % MOD
	disp = disp % 32
	local low = band(x, 2 ^ disp - 1)
	return rshift(x, disp) + lshift(low, 32 - disp)
end
 
local k = {
	0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
	0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
	0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
	0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
	0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
	0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
	0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
	0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
	0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
	0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
	0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
	0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
	0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
	0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
	0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
	0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
}
 
local function str2hexa(s)
	return (string.gsub(s, ".", function(c) return string.format("%02x", string.byte(c)) end))
end
 
local function num2s(l, n)
	local s = ""
	for i = 1, n do
			local rem = l % 256
			s = string.char(rem) .. s
			l = (l - rem) / 256
	end
	return s
end
 
local function s232num(s, i)
	local n = 0
	for i = i, i + 3 do n = n*256 + string.byte(s, i) end
	return n
end
 
local function preproc(msg, len)
	local extra = 64 - ((len + 9) % 64)
	len = num2s(8 * len, 8)
	msg = msg .. "\128" .. string.rep("\0", extra) .. len
	assert(#msg % 64 == 0)
	return msg
end
 
local function initH256(H)
	H[1] = 0x6a09e667
	H[2] = 0xbb67ae85
	H[3] = 0x3c6ef372
	H[4] = 0xa54ff53a
	H[5] = 0x510e527f
	H[6] = 0x9b05688c
	H[7] = 0x1f83d9ab
	H[8] = 0x5be0cd19
	return H
end
 
local function digestblock(msg, i, H)
	local w = {}
	for j = 1, 16 do w[j] = s232num(msg, i + (j - 1)*4) end
	for j = 17, 64 do
		local v = w[j - 15]
		local s0 = bxor(rrotate(v, 7), rrotate(v, 18), rshift(v, 3))
		v = w[j - 2]
		w[j] = w[j - 16] + s0 + w[j - 7] + bxor(rrotate(v, 17), rrotate(v, 19), rshift(v, 10))
	end

	local a, b, c, d, e, f, g, h = H[1], H[2], H[3], H[4], H[5], H[6], H[7], H[8]
	for i = 1, 64 do
		local s0 = bxor(rrotate(a, 2), rrotate(a, 13), rrotate(a, 22))
		local maj = bxor(band(a, b), band(a, c), band(b, c))
		local t2 = s0 + maj
		local s1 = bxor(rrotate(e, 6), rrotate(e, 11), rrotate(e, 25))
		local ch = bxor (band(e, f), band(bnot(e), g))
		local t1 = h + s1 + ch + k[i] + w[i]
		h, g, f, e, d, c, b, a = g, f, e, d + t1, c, b, a, t1 + t2
	end

	H[1] = band(H[1] + a)
	H[2] = band(H[2] + b)
	H[3] = band(H[3] + c)
	H[4] = band(H[4] + d)
	H[5] = band(H[5] + e)
	H[6] = band(H[6] + f)
	H[7] = band(H[7] + g)
	H[8] = band(H[8] + h)
end
 
local function make_hash(msg)
	msg = preproc(msg, #msg)
	local H = initH256({})
	for i = 1, #msg, 64 do digestblock(msg, i, H) end
	return str2hexa(num2s(H[1], 4) .. num2s(H[2], 4) .. num2s(H[3], 4) .. num2s(H[4], 4) ..
			num2s(H[5], 4) .. num2s(H[6], 4) .. num2s(H[7], 4) .. num2s(H[8], 4))
end

local function string_explode(str)
	local tbl = {}
	for i = 1, #str do
		tbl[i] = string.sub(str,1,1)
		str = string.sub(str,2)
	end
	return tbl
end

local function char_add(char1,char2)
	local str = string.byte(char1) + string.byte(char2)
	if str > 255 then str = str - 255 end
	str = string.char(str)
	return str
end

local function char_sub(char1,char2)
	local str = string.byte(char1) - string.byte(char2)
	if str < 0 then str = str + 255 end
	str = string.char(str)
	return str
end

function encrypt_msg(msg, password)
	local hash = make_hash(password)
	local msgtbl = string_explode(msg)
	local hashtbl = string_explode(hash)
	local hashlen = #hash
	local j
	for i = 1, #msgtbl do
		j = i % hashlen
		if j == 0 then j = hashlen end
		msgtbl[i] = char_add(msgtbl[i], hashtbl[j])
	end
	return table.concat(msgtbl,"")
end

function decrypt_msg(msg, password)
	local hash = make_hash(password)
	local msgtbl = string_explode(msg)
	local hashtbl = string_explode(hash)
	local hashlen = #hash
	local j
	for i = 1, #msgtbl do
		j = i % hashlen
		if j == 0 then j = hashlen end
		msgtbl[i] = char_sub(msgtbl[i], hashtbl[j])
	end
	return table.concat(msgtbl,"")
end

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