csprng.lua

-- KillaVanilla's RNG('s), composed of the Mersenne Twister RNG and the ISAAC algorithm.

-- Exposed functions:
-- initialize_mt_generator(seed) - Seed the Mersenne Twister RNG.
-- extract_mt() - Get a number from the Mersenne Twister RNG.
-- seed_from_mt(seed) - Seed the ISAAC RNG, optionally seeding the Mersenne Twister RNG beforehand.
-- generate_isaac() - Force a reseed.
-- cs_random(min, max) - Get a random number between min and max.

-- Helper functions:
local function toBinary(a) -- Convert from an integer to an arbitrary-length table of bits
    local b = {}
    local copy = a
    while true do
        table.insert(b, copy % 2)
        copy = bit.band(math.floor(copy / 2), 0x7FFFFFFF)
        if copy == 0 then
            break
        end
    end
    return b
end

local function fromBinary(a) -- Convert from an arbitrary-length table of bits (from toBinary) to an integer
    local dec = 0
    for i=#a, 1, -1 do
        dec = dec * 2 + a[i]
    end
    return dec
end

-- ISAAC internal state:
local aa, bb, cc = 0, 0, 0
local randrsl = {} -- Acts as entropy/seed-in. Fill to randrsl[256].
local mm = {} -- Fill to mm[256]. Acts as output.

-- Mersenne Twister State:
local MT = {} -- Twister state
local index = 0

-- Other variables for the seeding mechanism
local mtSeeded = false
local mtSeed = math.random(1, 2^32-1)

-- The Mersenne Twister can be used as an RNG for non-cryptographic purposes.
-- Here, we're using it to seed the ISAAC algorithm, which *can* be used for cryptographic purposes.

function initialize_mt_generator(seed)
    index = 0
    MT[0] = seed
    for i=1, 623 do
        local full = ( (1812433253 * bit.bxor(MT[i-1], bit.rshift(MT[i-1], 30) ) )+i)
        local b = toBinary(full)
        while #b > 32 do
            table.remove(b, 1)
        end
        MT[i] = fromBinary(b)
    end
end

local function generate_mt() -- Restock the MT with new random numbers.
    for i=0, 623 do
        local y = bit.band(MT[i], 0x80000000)
        y = y + bit.band(MT[(i+1)%624], 0x7FFFFFFF)
        MT[i] = bit.bxor(MT[(i+397)%624], bit.rshift(y, 1))
        if y % 2 == 1 then
            MT[i] = bit.bxor(MT[i], 0x9908B0DF)
        end
    end
end

function extract_mt(min, max) -- Get one number from the Mersenne Twister.
    if index == 0 then
        generate_mt()
    end
    local y = MT[index]
    min = min or 0
    max = max or 2^32-1
    --print("Accessing: MT["..index.."]...")
    y = bit.bxor(y, bit.rshift(y, 11) )
    y = bit.bxor(y, bit.band(bit.lshift(y, 7), 0x9D2C5680) )
    y = bit.bxor(y, bit.band(bit.lshift(y, 15), 0xEFC60000) )
    y = bit.bxor(y, bit.rshift(y, 18) )
    index = (index+1) % 624
    return (y % max)+min
end

function seed_from_mt(seed) -- seed ISAAC with numbers from the MT:
    if seed then
        mtSeeded = false
        mtSeed = seed
    end
    if not mtSeeded or (math.random(1, 100) == 50) then -- Always seed the first time around. Otherwise, seed approximately once per 100 times.
        initialize_mt_generator(mtSeed)
        mtSeeded = true
        mtSeed = extract_mt()
    end
    for i=1, 256 do
        randrsl[i] = extract_mt()
    end
end

local function mix(a,b,c,d,e,f,g,h)
    a = a % (2^32-1)
    b = b % (2^32-1)
    c = c % (2^32-1)
    d = d % (2^32-1)
    e = e % (2^32-1)
    f = f % (2^32-1)
    g = g % (2^32-1)
    h = h % (2^32-1)
     a = bit.bxor(a, bit.lshift(b, 11))
     d = (d + a) % (2^32-1)
     b = (b + c) % (2^32-1)
     b = bit.bxor(b, bit.rshift(c, 2) )
     e = (e + b) % (2^32-1)
     c = (c + d) % (2^32-1)
     c = bit.bxor(c, bit.lshift(d, 8) )
     f = (f + c) % (2^32-1)
     d = (d + e) % (2^32-1)
     d = bit.bxor(d, bit.rshift(e, 16) )
     g = (g + d) % (2^32-1)
     e = (e + f) % (2^32-1)
     e = bit.bxor(e, bit.lshift(f, 10) )
     h = (h + e) % (2^32-1)
     f = (f + g) % (2^32-1)
     f = bit.bxor(f, bit.rshift(g, 4) )
     a = (a + f) % (2^32-1)
     g = (g + h) % (2^32-1)
     g = bit.bxor(g, bit.lshift(h, 8) )
     b = (b + g) % (2^32-1)
     h = (h + a) % (2^32-1)
     h = bit.bxor(h, bit.rshift(a, 9) )
     c = (c + h) % (2^32-1)
     a = (a + b) % (2^32-1)
     return a,b,c,d,e,f,g,h
end

local function isaac()
    local x, y = 0, 0
    for i=1, 256 do
        x = mm[i]
        if (i % 4) == 0 then
            aa = bit.bxor(aa, bit.lshift(aa, 13))
        elseif (i % 4) == 1 then
            aa = bit.bxor(aa, bit.rshift(aa, 6))
        elseif (i % 4) == 2 then
            aa = bit.bxor(aa, bit.lshift(aa, 2))
        elseif (i % 4) == 3 then
            aa = bit.bxor(aa, bit.rshift(aa, 16))
        end
        aa = (mm[ ((i+128) % 256)+1 ] + aa) % (2^32-1)
        y = (mm[ (bit.rshift(x, 2) % 256)+1 ] + aa + bb) % (2^32-1)
        mm[i] = y
        bb = (mm[ (bit.rshift(y,10) % 256)+1 ] + x) % (2^32-1)
        randrsl[i] = bb
    end
end

local function randinit(flag)
    local a,b,c,d,e,f,g,h = 0x9e3779b9,0x9e3779b9,0x9e3779b9,0x9e3779b9,0x9e3779b9,0x9e3779b9,0x9e3779b9,0x9e3779b9-- 0x9e3779b9 is the golden ratio
    aa = 0
    bb = 0
    cc = 0
    for i=1,4 do
        a,b,c,d,e,f,g,h = mix(a,b,c,d,e,f,g,h)
    end
    for i=1, 256, 8 do
        if flag then
            a = (a + randrsl[i]) % (2^32-1)
            b = (b + randrsl[i+1]) % (2^32-1)
            c = (c + randrsl[i+2]) % (2^32-1)
            d = (b + randrsl[i+3]) % (2^32-1)
            e = (e + randrsl[i+4]) % (2^32-1)
            f = (f + randrsl[i+5]) % (2^32-1)
            g = (g + randrsl[i+6]) % (2^32-1)
            h = (h + randrsl[i+7]) % (2^32-1)
        end
        a,b,c,d,e,f,g,h = mix(a,b,c,d,e,f,g,h)
        mm[i] = a
        mm[i+1] = b
        mm[i+2] = c
        mm[i+3] = d
        mm[i+4] = e
        mm[i+5] = f
        mm[i+6] = g
        mm[i+7] = h
    end
    
    if flag then
        for i=1, 256, 8 do
            a = (a + randrsl[i]) % (2^32-1)
            b = (b + randrsl[i+1]) % (2^32-1)
            c = (c + randrsl[i+2]) % (2^32-1)
            d = (b + randrsl[i+3]) % (2^32-1)
            e = (e + randrsl[i+4]) % (2^32-1)
            f = (f + randrsl[i+5]) % (2^32-1)
            g = (g + randrsl[i+6]) % (2^32-1)
            h = (h + randrsl[i+7]) % (2^32-1)
            a,b,c,d,e,f,g,h = mix(a,b,c,d,e,f,g,h)
            mm[i] = a
            mm[i+1] = b
            mm[i+2] = c
            mm[i+3] = d
            mm[i+4] = e
            mm[i+5] = f
            mm[i+6] = g
            mm[i+7] = h
        end
    end
    isaac()
    randcnt = 256
end

function generate_isaac(entropy)
    aa = 0
    bb = 0
    cc = 0
    if entropy and #entropy >= 256 then
        for i=1, 256 do
            randrsl[i] = entropy[i]
        end
    else
        print("2. seed_from_mt")
        seed_from_mt()
    end
    for i=1, 256 do
        mm[i] = 0
    end
    randinit(true)
    isaac()
    isaac() -- run isaac twice
end

local function getRandom()
    if #mm > 0 then
        return table.remove(mm, 1)
    else
        print("generating_isaac")
        generate_isaac()
        return table.remove(mm, 1)
    end
end

function cs_random(min, max)
    if not max then
        max = 2^32-1
    end
    if not min then
        min = 0
    end
    return (getRandom() % max) + min
end