#!/usr/bin/python
# -*- coding: utf8 -*-

"""
This is a port of Chris Veness' AES implementation: http://www.movable-type.co.uk/scripts/aes.html
Copyright ©2005-2008 Chris Veness. Right of free use is granted for all
commercial or non-commercial use. No warranty of any form is offered.
Ported in 2009 by Markus Birth <markus@birth-online.de>
"""

import base64
import datetime
import math
import time

"""Sbox is pre-computed multiplicative inverse in GF(2^8) used in SubBytes and KeyExpansion [§5.1.1]"""
Sbox = [
    0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
    0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
    0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
    0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
    0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
    0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
    0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
    0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
    0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
    0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
    0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
    0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
    0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
    0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
    0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
    0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16
]

"""Rcon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2]"""
Rcon = [
    [0x00, 0x00, 0x00, 0x00],
    [0x01, 0x00, 0x00, 0x00],
    [0x02, 0x00, 0x00, 0x00],
    [0x04, 0x00, 0x00, 0x00],
    [0x08, 0x00, 0x00, 0x00],
    [0x10, 0x00, 0x00, 0x00],
    [0x20, 0x00, 0x00, 0x00],
    [0x40, 0x00, 0x00, 0x00],
    [0x80, 0x00, 0x00, 0x00],
    [0x1b, 0x00, 0x00, 0x00],
    [0x36, 0x00, 0x00, 0x00]
]


def Cipher(input, w):
    Nb = 4
    Nr = len(w)/Nb - 1

    state = [ [0] * Nb, [0] * Nb, [0] * Nb, [0] * Nb ]
    for i in range(0, 4*Nb): state[i%4][i//4] = input[i]

    state = AddRoundKey(state, w, 0, Nb)

    for round in range(1, Nr):
        state = SubBytes(state, Nb)
        state = ShiftRows(state, Nb)
        state = MixColumns(state, Nb)
        state = AddRoundKey(state, w, round, Nb)

    state = SubBytes(state, Nb)
    state = ShiftRows(state, Nb)
    state = AddRoundKey(state, w, Nr, Nb)

    output = [0] * 4*Nb
    for i in range(4*Nb): output[i] = state[i%4][i//4]
    return output

def SubBytes(s, Nb):
    for r in range(4):
        for c in range(Nb):
            s[r][c] = Sbox[s[r][c]]
    return s

def ShiftRows(s, Nb):
    t = [0] * 4
    for r in range (1,4):
        for c in range(4): t[c] = s[r][(c+r)%Nb]
        for c in range(4): s[r][c] = t[c]
    return s

def MixColumns(s, Nb):
    for c in range(4):
        a = [0] * 4
        b = [0] * 4
        for i in range(4):
            a[i] = s[i][c]
            b[i] = s[i][c]<<1 ^ 0x011b if s[i][c]&0x80 else s[i][c]<<1
        s[0][c] = b[0] ^ a[1] ^ b[1] ^ a[2] ^ a[3]
        s[1][c] = a[0] ^ b[1] ^ a[2] ^ b[2] ^ a[3]
        s[2][c] = a[0] ^ a[1] ^ b[2] ^ a[3] ^ b[3]
        s[3][c] = a[0] ^ b[0] ^ a[1] ^ a[2] ^ b[3]
    return s

def AddRoundKey(state, w, rnd, Nb):
    for r in range(4):
        for c in range(Nb):
            state[r][c] ^= w[rnd*4+c][r]
    return state

def KeyExpansion(key):
    Nb = 4
    Nk = len(key)/4
    Nr = Nk + 6

    w = [0] * Nb*(Nr+1)
    temp = [0] * 4

    for i in range(Nk):
        r = [key[4*i], key[4*i+1], key[4*i+2], key[4*i+3]]
        w[i] = r

    for i in range(Nk, Nb*(Nr+1)):
        w[i] = [0] * 4
        for t in range(4): temp[t] = w[i-1][t]
        if i%Nk == 0:
            temp = SubWord(RotWord(temp))
            for t in range(4): temp[t] ^= Rcon[i/Nk][t]
        elif Nk>6 and i%Nk == 4:
            temp = SubWord(temp)
        for t in range(4): w[i][t] = w[i-Nk][t] ^ temp[t]
    return w

def SubWord(w):
    for i in range(4): w[i] = Sbox[w[i]]
    return w

def RotWord(w):
    tmp = w[0]
    for i in range(3): w[i] = w[i+1]
    w[3] = tmp
    return w

def encrypt(plaintext, password, nBits):
    blockSize = 16
    if not nBits in (128, 192, 256): return ""
#    plaintext = plaintext.encode("utf-8")
#    password  = password.encode("utf-8")
    nBytes = nBits//8
    pwBytes = [0] * nBytes
    for i in range(nBytes): pwBytes[i] = 0 if i>=len(password) else ord(password[i])
    key = Cipher(pwBytes, KeyExpansion(pwBytes))
    key += key[:nBytes-16]

    counterBlock = [0] * blockSize
    now = datetime.datetime.now()
    nonce = time.mktime( now.timetuple() )*1000 + now.microsecond//1000
    nonceSec = int(nonce // 1000)
    nonceMs  = int(nonce % 1000)

    for i in range(4): counterBlock[i] = urs(nonceSec, i*8) & 0xff
    for i in range(4): counterBlock[i+4] = nonceMs & 0xff

    ctrTxt = ""
    for i in range(8): ctrTxt += chr(counterBlock[i])

    keySchedule = KeyExpansion(key)

    blockCount = int(math.ceil(float(len(plaintext))/float(blockSize)))
    ciphertxt = [0] * blockCount

    for b in range(blockCount):
        for c in range(4): counterBlock[15-c] = urs(b, c*8) & 0xff
        for c in range(4): counterBlock[15-c-4] = urs(b/0x100000000, c*8)

        cipherCntr = Cipher(counterBlock, keySchedule)

        blockLength = blockSize if b<blockCount-1 else (len(plaintext)-1)%blockSize+1
        cipherChar = [0] * blockLength

        for i in range(blockLength):
            cipherChar[i] = cipherCntr[i] ^ ord(plaintext[b*blockSize+i])
            cipherChar[i] = chr( cipherChar[i] )
        ciphertxt[b] = ''.join(cipherChar)

    ciphertext = ctrTxt + ''.join(ciphertxt)
    ciphertext = base64.b64encode(ciphertext)

    return ciphertext

def decrypt(ciphertext, password, nBits):
    blockSize = 16
    if not nBits in (128, 192, 256): return ""
    ciphertext = base64.b64decode(ciphertext)
#    password = password.encode("utf-8")

    nBytes = nBits//8
    pwBytes = [0] * nBytes
    for i in range(nBytes): pwBytes[i] = 0 if i>=len(password) else ord(password[i])
    key = Cipher(pwBytes, KeyExpansion(pwBytes))
    key += key[:nBytes-16]

    counterBlock = [0] * blockSize
    ctrTxt = ciphertext[:8]
    for i in range(8): counterBlock[i] = ord(ctrTxt[i])

    keySchedule = KeyExpansion(key)

    nBlocks = int( math.ceil( float(len(ciphertext)-8) / float(blockSize) ) )
    ct = [0] * nBlocks
    for b in range(nBlocks):
        ct[b] = ciphertext[8+b*blockSize : 8+b*blockSize+blockSize]
    ciphertext = ct

    plaintxt = [0] * len(ciphertext)

    for b in range(nBlocks):
        for c in range(4): counterBlock[15-c] = urs(b, c*8) & 0xff
        for c in range(4): counterBlock[15-c-4] = urs( int( float(b+1)/0x100000000-1 ), c*8) & 0xff

        cipherCntr = Cipher(counterBlock, keySchedule)

        plaintxtByte = [0] * len(ciphertext[b])
        for i in range(len(ciphertext[b])):
            plaintxtByte[i] = cipherCntr[i] ^ ord(ciphertext[b][i])
            plaintxtByte[i] = chr(plaintxtByte[i])
        plaintxt[b] = "".join(plaintxtByte)

    plaintext = "".join(plaintxt)
 #   plaintext = plaintext.decode("utf-8")
    return plaintext

def urs(a, b):
    a &= 0xffffffff
    b &= 0x1f
    if a&0x80000000 and b>0:
        a = (a>>1) & 0x7fffffff
        a = a >> (b-1)
    else:
        a = (a >> b)
    return a
