77 lines
1.9 KiB
Lua
77 lines
1.9 KiB
Lua
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local string = require("string")
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local bit = require("bit")
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module("rc4")
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local function swapStateIndicies(state)
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local t = state.schedule[state.i]
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state.schedule[state.i] = state.schedule[state.j]
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state.schedule[state.j] = t
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end
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local function swapIndicies(sch, i, j)
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local t = sch[i]
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sch[i] = sch[j]
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sch[j] = t
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end
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local function createKeySchedule(sKey)
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local nKeyLength = string.len(sKey)
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local tKey = { string.byte(sKey, 1, nKeyLength) }
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if nKeyLength < 1 or nKeyLength > 256 then
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error("Key length out of bounds. 1 <= length <= 256")
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end
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local tSch = {}
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for i = 0, 255 do
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tSch[i] = i
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end
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local j = 0
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for i = 0, 255 do
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j = (j + tSch[i] + tKey[(i % nKeyLength) + 1]) % 256
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swapIndicies(tSch, i, j)
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end
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return tSch
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end
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local function keyGeneration(state, nCount)
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local K = {}
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for i = 1, nCount do
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state.i = (state.i + 1) % 256
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state.j = (state.j + state.schedule[state.i - 1]) % 256
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swapStateIndicies(state)
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K[#K+1] = state.schedule[(state.schedule[ state.i - 1] + state.schedule[ state.j - 1] - 1) % 256]
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end
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return K
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end
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local function cipher(sMessage, state)
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local nCount = string.len(sMessage)
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local K = keyGeneration(state, nCount)
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local sOutput = ""
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for i = 1, nCount do
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sOutput = sOutput .. string.char(bit.bxor( K[i], string.byte(sMessage, i)))
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end
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return sOutput
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end
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function new(sKey, bEncryption)
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local tSch = createKeySchedule(sKey)
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local nS1 = 0
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local nS2 = 0
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local state = {
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i = nS1,
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j = nS2,
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schedule = tSch
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}
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local tSession = {}
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local sFuncName = "decrypt"
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if bEncryption then
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sFuncName = "encrypt"
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end
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tSession[sFuncName] = function(sMessage)
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local sOutput = cipher(sMessage, state)
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return sOutput
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end
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return tSession
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end |