Curated (table) Xor cipher benchmarks across LuaJIT, LuaJIT interpreter and Cobalt (ComputerCraft: Tweaked)

xor-benchmark.lua

-- Note: do use local(ization) for better performance when JIT is off
local pairs, ipairs, next, rawset, rawget, bit_bxor = pairs, ipairs, next, rawset, rawget, bit32 and bit32.bxor or bit.bxor
local Xor0 = function(t, k)
  -- assume `t` and `k` are (non empty) byte arrays (sequential & numeric indexed Lua tables)
  local x = {}
  for i = 1, #t do
    x[i] = bit_bxor(t[i], k[((i - 1) % #k) + 1])
  end
  return x
end
local XorRaw0 = function(t, k)
  local x = {}
  for i = 1, #t do
    rawset(x, i, bit_bxor(rawget(t, i), rawget(k, ((i - 1) % #k) + 1)))
  end
  return x
end
local XorInv0 = function(t, k)
  local x = {}
  for i = #t, 1, -1 do
    x[i] = bit_bxor(t[i], k[((i - 1) % #k) + 1])
  end
  return x
end
local XorRawInv0 = function(t, k)
  local x = {}
  for i = #t, 1, -1 do
    rawset(x, i, bit_bxor(rawget(t, i), rawget(k, ((i - 1) % #k) + 1)))
  end
  return x
end
-- self-modify variants:
local Xor1 = function(t, k)
  for i = 1, #t do
    t[i] = bit_bxor(t[i], k[((i - 1) % #k) + 1])
  end
end
local XorRaw1 = function(t, k)
  for i = 1, #t do
    rawset(t, i, bit_bxor(rawget(t, i), rawget(k, ((i - 1) % #k) + 1)))
  end
end
local XorInv1 = function(t, k)
  for i = #t, 1, -1 do
    t[i] = bit_bxor(t[i], k[((i - 1) % #k) + 1])
  end
end
local XorRawInv1 = function(t, k)
  for i = #t, 1, -1 do
    rawset(t, i, bit_bxor(rawget(t, i), rawget(k, ((i - 1) % #k) + 1)))
  end
end

local Xor2 = function(t, k)
  local j = 1
  for i = 1, #t do
    t[i] = bit_bxor(t[i], k[j])
    j = j + 1
    if j > #k then
      j = 1
    end
  end
end

local Xor3 = function(t, k)
  local l, j = #k, 1
  for i = 1, #t do
    t[i] = bit_bxor(t[i], k[j])
    j = j + 1
    if j > l then
      j = 1
    end
  end
end

local Xor4 = function(t, k)
  for i, b in next, t do
    t[i] = bit_bxor(b, k[((i - 1) % #k) + 1])
  end
end

local Xor5 = function(t, k)
  local j = 1
  for i, b in next, t do
    t[i] = bit_bxor(b, k[j])
    j = j + 1
    if j > #k then
      j = 1
    end
  end
end

local Xor6 = function(t, k)
  local l, j = #k, 1
  for i, b in next, t do
    t[i] = bit_bxor(b, k[j])
    j = j + 1
    if j > l then
      j = 1
    end
  end
end

local Xor7 = function(t, k)
  --assert(#k >= #t)
  for i, b in next, t do
    t[i] = bit_bxor(b, k[i])
  end
end

local XorRaw7 = function(t, k)
  for i, b in next, t do
    rawset(t, i, bit_bxor(b, rawget(k, i)))
  end
end

local XorPairs7 = function(t, k)
  for i, b in pairs(t) do
    t[i] = bit_bxor(b, k[i])
  end
end

local XorIpairs7 = function(t, k)
  for i, b in ipairs(t) do
    t[i] = bit_bxor(b, k[i])
  end
end

math.randomseed(1)
local SECRET, KEY = {}, {}
for i = 1, 8 do SECRET[i] = math.random(0, 0xFF) end
for i = 1, 8 do KEY[i] = math.random(0, 0xFF) end -- for optimal performance & security, make sure to satisfy: #KEY >= #SECRET
local TIME = jit and os.clock() or (os.epoch 'utc' / 1000) -- normalize time between our environments
-- shorter is better; best times are starred with **; all times are measured in seconds
-- average execution time    :(JIT on) | (JIT off) | (CC:T)
for _ = 1, 1000000 do --sterr:   0.0005| 0.006     | 0.038
  --Xor0(SECRET, KEY)       --   0.635 | 0.903     | 5.0801 - 5.1428
  --XorRaw0(SECRET, KEY)    --   0.63  | 1.345     | too long
  --XorInv0(SECRET, KEY)    --   0.525 | 0.852     | 5.7576 - 5.7826
  --XorRawInv0(SECRET, KEY) --   0.52  | 1.21      | too long
  --- self-modify variants ---
  --Xor1(SECRET, KEY)       --   0.111 | 0.474     | 4.1328
  --XorRaw1(SECRET, KEY)    --   0.111 | 0.867     | too long
  --XorInv1(SECRET, KEY)    --   0.112 | 0.477     | 4.1224
  --XorRawInv1(SECRET, KEY) --   0.111 | 0.873     | too long
  --Xor2(SECRET, KEY)       --   0.065 | 0.39      | 3.7272
  --Xor3(SECRET, KEY)       -- **0.065 | 0.316     | 3.3189    ; fastest with JIT on
  --Xor4(SECRET, KEY)       --   0.157 | 0.468     | 4.8955
  --Xor5(SECRET, KEY)       --   0.108 | 0.362     | 4.4412
  --Xor6(SECRET, KEY)       --   0.112 | 0.3       | 3.9734
  --Xor7(SECRET, KEY)       --   0.09  | 0.245**   | 3.3026**  ; fastest with JIT off (aka with [JIT] interpreter) & Cobalt
  --XorRaw7(SECRET, KEY)    --   0.09  | 0.602     | 6.1845
  --XorPairs7(SECRET, KEY)  --   0.09  | 0.255     | 3.3987
  --XorIpairs7(SECRET, KEY) --   0.057 | 0.332     | 3.3995
end
print((jit and os.clock() or (os.epoch 'utc' / 1000)) - TIME)