-- RC4-- http://en.wikipedia.org/wiki/RC4function KSA(key)    local key_len = string.len(key)    local S = {}    local key_byte = {}    for i = 0, 255 do        S[i] = i    end    for i = 1, key_len do        key_byte[i-1] = string.byte(key, i, i)    end    local j = 0    for i = 0, 255 do        j = (j + S[i] + key_byte[i % key_len]) % 256        S[i], S[j] = S[j], S[i]    end    return Sendfunction PRGA(S, text_len)    local i = 0    local j = 0    local K = {}    for n = 1, text_len do        i = (i + 1) % 256        j = (j + S[i]) % 256        S[i], S[j] = S[j], S[i]        K[n] = S[(S[i] + S[j]) % 256]    end    return Kendfunction RC4(key, text)    local text_len = string.len(text)    local S = KSA(key)            local K = PRGA(S, text_len)     return output(K, text)endfunction output(S, text)    local len = string.len(text)    local c = nil    local res = {}    for i = 1, len do        c = string.byte(text, i, i)        res[i] = string.char(bxor(S[i], c))    end    return table.concat(res)end--------------------------------------------bit wise------------------------------------------local bit_op = {}function bit_op.cond_and(r_a, r_b)    return (r_a + r_b == 2) and 1 or 0endfunction bit_op.cond_xor(r_a, r_b)    return (r_a + r_b == 1) and 1 or 0endfunction bit_op.cond_or(r_a, r_b)    return (r_a + r_b > 0) and 1 or 0endfunction bit_op.base(op_cond, a, b)    -- bit operation    if a < b then        a, b = b, a    end    local res = 0    local shift = 1    while a ~= 0 do        r_a = a % 2        r_b = b % 2           res = shift * bit_op[op_cond](r_a, r_b) + res         shift = shift * 2        a = math.modf(a / 2)        b = math.modf(b / 2)    end    return resendfunction bxor(a, b)    return bit_op.base(‘cond_xor‘, a, b)endfunction band(a, b)    return bit_op.base(‘cond_and‘, a, b)endfunction bor(a, b)    return bit_op.base(‘cond_or‘, a, b)end--key = "Key"--text = "Plaintext"--K = RC4(key, text)--print (K)--text = RC4(key, K)--print (text)----key = "Wiki"--text = "pedia"--K = RC4(key, text)--print (K)----key = "Secret"--text = "Attack at dawn"--K = RC4(key, text)--print (K)