Spritz Encryption Routines

spritz.lua

S = {}
i,j,k,z,a,v=0,0,0,0,0,0
w=1
N=2^9 --2^8 or 8bits
D=math.ceil(math.sqrt(N))

print("N:",N)
print("D:",D)

function InitializeState(N)
	i,j,k,z,a=0,0,0,0,0
	w=1
	for v = 0, N-1 do
		S[v] = v
	end
end

function Absorb(I)
	for v = 0, #I-1 do
		AbsorbByte(I[v])
	end
end

function AbsorbByte(b)
	AbsorbNibble(LOW(b))
	AbsorbNibble(HIGH(b))
end

function LOW(b)
	return b % D
end

function HIGH(b)
	return math.floor(b / D)
end

function AbsorbNibble(x)
	if a == math.floor(N/2) then
		Shuffle()
	end
	--Swap(S[a], S[math.floor(N/2) + x])
	Swap(S, a, math.floor(N/2)+x)
	a = (a + 1) % N
end

function Swap(array, index1, index2)
	array[index1], array[index2] = array[index2], array[index1]
end

function AbsorbStop()
	if a == math.floor(N/2) then
		Shuffle()
	end
	a = (a + 1) % N
end

function Shuffle()
	Whip(2*N)
	Crush()
	Whip(2*N)
	Crush()
	Whip(2*N)
	a = 0
end

function Whip(r)
	for v = 0, r-1 do
		Update()
	end
	repeat
		w = (w + 1) % N
	until gcd(w, N) == 1
end

function gcd(a,b)
	if b ~= 0 then
		return gcd(b, a % b)
	else
		return math.abs(a)
	end
end

function Crush()
	for v = 0, math.floor(N/2)-1 do
		if S[v] > S[(N - 1 - v) % N] then
			--Swap(S[v], S[N - 1 - v])
			Swap(S, v, (N - 1 - v) % N)
		end
	end
end

function Squeeze(r)
	if a > 0 then
		Shuffle()
	end
	P=nil;P={};
	for v = 0, r-1 do
		P[v] = Drip()
	end
	return P
end

function Drip()
	if a > 0 then
		Shuffle()
	end
	Update()
	return Output()
end

function Update()
	i = (i + w) % N
	j = (k + S[(j + S[i]) % N]) % N
	k = (i + k + S[j]) % N
	Swap(S,i,j)
end

function Output()
	--z = S[j + S[i + S[z + k]]]
	z = S[(j + S[(i + S[(z + k) % N]) % N]) % N]
	--print("OUTPUT\tz:",z)
	return z
end

InitializeState(N)
print(table.concat(Squeeze(D),", "))