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1 # -*- coding: utf-8 -*- |
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2 |
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3 # |
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4 # aes.py: implements AES - Advanced Encryption Standard |
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5 # from the SlowAES project, http://code.google.com/p/slowaes/ |
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6 # |
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7 # Copyright (c) 2008 Josh Davis ( http://www.josh-davis.org ), |
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8 # Alex Martelli ( http://www.aleax.it ) |
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9 # |
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10 # Ported from C code written by Laurent Haan |
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11 # ( http://www.progressive-coding.com ) |
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12 # |
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13 # Licensed under the Apache License, Version 2.0 |
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14 # http://www.apache.org/licenses/ |
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15 # |
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16 |
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17 # |
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18 # Ported to Python3 |
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19 # |
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20 # Copyright (c) 2011 - 2022 Detlev Offenbach <detlev@die-offenbachs.de> |
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21 # |
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22 |
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23 """ |
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24 Module implementing classes for encryption according |
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25 Advanced Encryption Standard. |
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26 """ |
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27 |
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28 import os |
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29 import math |
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30 |
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31 |
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32 def append_PKCS7_padding(b): |
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33 """ |
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34 Function to pad the given data to a multiple of 16-bytes by PKCS7 padding. |
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35 |
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36 @param b data to be padded (bytes) |
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37 @return padded data (bytes) |
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38 """ |
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39 numpads = 16 - (len(b) % 16) |
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40 return b + numpads * bytes(chr(numpads), encoding="ascii") |
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41 |
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42 |
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43 def strip_PKCS7_padding(b): |
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44 """ |
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45 Function to strip off PKCS7 padding. |
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46 |
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47 @param b data to be stripped (bytes) |
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48 @return stripped data (bytes) |
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49 @exception ValueError data padding is invalid |
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50 """ |
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51 if len(b) % 16 or not b: |
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52 raise ValueError( |
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53 "Data of len {0} can't be PCKS7-padded".format(len(b))) |
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54 numpads = b[-1] |
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55 if numpads > 16: |
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56 raise ValueError( |
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57 "Data ending with {0} can't be PCKS7-padded".format(b[-1])) |
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58 return b[:-numpads] |
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59 |
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60 |
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61 class AES: |
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62 """ |
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63 Class implementing the Advanced Encryption Standard algorithm. |
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64 """ |
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65 # valid key sizes |
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66 KeySize = { |
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67 "SIZE_128": 16, |
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68 "SIZE_192": 24, |
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69 "SIZE_256": 32, |
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70 } |
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71 |
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72 # Rijndael S-box |
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73 sbox = [0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, |
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74 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, |
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75 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, |
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76 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, |
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77 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, |
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78 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, |
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79 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, |
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80 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, |
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81 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, |
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82 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, |
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83 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, |
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84 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, |
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85 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, |
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86 0x73, 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, |
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87 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, |
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88 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, |
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89 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, |
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90 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, |
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91 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70, |
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92 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, |
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93 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, |
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94 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, |
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95 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, |
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96 0x54, 0xbb, 0x16] |
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97 |
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98 # Rijndael Inverted S-box |
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99 rsbox = [0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, |
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100 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, |
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101 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, |
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102 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, |
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103 0x42, 0xfa, 0xc3, 0x4e, 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, |
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104 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, |
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105 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, |
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106 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, |
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107 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 0x90, 0xd8, 0xab, |
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108 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, |
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109 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, |
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110 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41, |
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111 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, |
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112 0x73, 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, |
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113 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, |
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114 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, |
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115 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, |
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116 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, |
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117 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 0x60, |
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118 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, |
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119 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, |
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120 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 0x17, 0x2b, |
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121 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, |
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122 0x21, 0x0c, 0x7d] |
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123 |
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124 # Rijndael Rcon |
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125 Rcon = [0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, |
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126 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, |
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127 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, |
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128 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, |
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129 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, |
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130 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, |
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131 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, |
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132 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, |
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133 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, |
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134 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, |
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135 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, |
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136 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, |
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137 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, |
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138 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, |
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139 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, |
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140 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, |
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141 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, |
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142 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, |
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143 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, |
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144 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, |
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145 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, |
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146 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, |
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147 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, |
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148 0xe8, 0xcb] |
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149 |
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150 def __getSBoxValue(self, num): |
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151 """ |
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152 Private method to retrieve a given S-Box value. |
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153 |
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154 @param num position of the value (integer) |
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155 @return value of the S-Box (integer) |
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156 """ |
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157 return self.sbox[num] |
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158 |
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159 def __getSBoxInvert(self, num): |
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160 """ |
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161 Private method to retrieve a given Inverted S-Box value. |
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162 |
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163 @param num position of the value (integer) |
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164 @return value of the Inverted S-Box (integer) |
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165 """ |
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166 return self.rsbox[num] |
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167 |
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168 def __rotate(self, data): |
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169 """ |
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170 Private method performing Rijndael's key schedule rotate operation. |
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171 |
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172 Rotate the data word eight bits to the left: eg, |
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173 rotate(1d2c3a4f) == 2c3a4f1d. |
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174 |
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175 @param data data of size 4 (bytearray) |
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176 @return rotated data (bytearray) |
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177 """ |
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178 return data[1:] + data[:1] |
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179 |
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180 def __getRconValue(self, num): |
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181 """ |
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182 Private method to retrieve a given Rcon value. |
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183 |
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184 @param num position of the value (integer) |
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185 @return Rcon value (integer) |
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186 """ |
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187 return self.Rcon[num] |
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188 |
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189 def __core(self, data, iteration): |
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190 """ |
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191 Private method performing the key schedule core operation. |
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192 |
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193 @param data data to operate on (bytearray) |
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194 @param iteration iteration counter (integer) |
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195 @return modified data (bytearray) |
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196 """ |
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197 # rotate the 32-bit word 8 bits to the left |
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198 data = self.__rotate(data) |
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199 # apply S-Box substitution on all 4 parts of the 32-bit word |
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200 for i in range(4): |
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201 data[i] = self.__getSBoxValue(data[i]) |
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202 # XOR the output of the rcon operation with i to the first part |
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203 # (leftmost) only |
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204 data[0] = data[0] ^ self.__getRconValue(iteration) |
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205 return data |
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206 |
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207 def __expandKey(self, key, size, expandedKeySize): |
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208 """ |
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209 Private method performing Rijndael's key expansion. |
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210 |
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211 Expands a 128, 192 or 256 bit key into a 176, 208 or 240 bit key. |
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212 |
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213 @param key key to be expanded (bytes or bytearray) |
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214 @param size size of the key in bytes (16, 24 or 32) |
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215 @param expandedKeySize size of the expanded key (integer) |
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216 @return expanded key (bytearray) |
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217 """ |
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218 # current expanded keySize, in bytes |
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219 currentSize = 0 |
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220 rconIteration = 1 |
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221 expandedKey = bytearray(expandedKeySize) |
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222 |
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223 # set the 16, 24, 32 bytes of the expanded key to the input key |
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224 for j in range(size): |
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225 expandedKey[j] = key[j] |
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226 currentSize += size |
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227 |
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228 while currentSize < expandedKeySize: |
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229 # assign the previous 4 bytes to the temporary value t |
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230 t = expandedKey[currentSize - 4:currentSize] |
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231 |
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232 # every 16, 24, 32 bytes we apply the core schedule to t |
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233 # and increment rconIteration afterwards |
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234 if currentSize % size == 0: |
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235 t = self.__core(t, rconIteration) |
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236 rconIteration += 1 |
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237 # For 256-bit keys, we add an extra sbox to the calculation |
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238 if ( |
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239 size == self.KeySize["SIZE_256"] and |
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240 ((currentSize % size) == 16) |
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241 ): |
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242 for ll in range(4): |
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243 t[ll] = self.__getSBoxValue(t[ll]) |
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244 |
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245 # We XOR t with the four-byte block 16, 24, 32 bytes before the new |
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246 # expanded key. This becomes the next four bytes in the expanded |
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247 # key. |
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248 for m in range(4): |
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249 expandedKey[currentSize] = ( |
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250 expandedKey[currentSize - size] ^ t[m] |
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251 ) |
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252 currentSize += 1 # __IGNORE_WARNING_Y113__ |
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253 |
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254 return expandedKey |
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255 |
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256 def __addRoundKey(self, state, roundKey): |
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257 """ |
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258 Private method to add (XORs) the round key to the state. |
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259 |
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260 @param state state to be changed (bytearray) |
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261 @param roundKey key to be used for the modification (bytearray) |
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262 @return modified state (bytearray) |
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263 """ |
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264 buf = state[:] |
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265 for i in range(16): |
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266 buf[i] ^= roundKey[i] |
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267 return buf |
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268 |
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269 def __createRoundKey(self, expandedKey, roundKeyPointer): |
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270 """ |
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271 Private method to create a round key. |
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272 |
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273 @param expandedKey expanded key to be used (bytearray) |
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274 @param roundKeyPointer position within the expanded key (integer) |
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275 @return round key (bytearray) |
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276 """ |
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277 roundKey = bytearray(16) |
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278 for i in range(4): |
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279 for j in range(4): |
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280 roundKey[j * 4 + i] = expandedKey[roundKeyPointer + i * 4 + j] |
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281 return roundKey |
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282 |
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283 def __galois_multiplication(self, a, b): |
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284 """ |
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285 Private method to perform a Galois multiplication of 8 bit characters |
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286 a and b. |
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287 |
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288 @param a first factor (byte) |
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289 @param b second factor (byte) |
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290 @return result (byte) |
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291 """ |
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292 p = 0 |
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293 for _counter in range(8): |
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294 if b & 1: |
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295 p ^= a |
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296 hi_bit_set = a & 0x80 |
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297 a <<= 1 |
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298 # keep a 8 bit |
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299 a &= 0xFF |
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300 if hi_bit_set: |
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301 a ^= 0x1b |
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302 b >>= 1 |
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303 return p |
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304 |
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305 def __subBytes(self, state, isInv): |
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306 """ |
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307 Private method to substitute all the values from the state with the |
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308 value in the SBox using the state value as index for the SBox. |
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309 |
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310 @param state state to be worked on (bytearray) |
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311 @param isInv flag indicating an inverse operation (boolean) |
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312 @return modified state (bytearray) |
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313 """ |
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314 state = state[:] |
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315 getter = self.__getSBoxInvert if isInv else self.__getSBoxValue |
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316 for i in range(16): |
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317 state[i] = getter(state[i]) |
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318 return state |
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319 |
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320 def __shiftRows(self, state, isInv): |
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321 """ |
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322 Private method to iterate over the 4 rows and call __shiftRow() with |
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323 that row. |
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324 |
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325 @param state state to be worked on (bytearray) |
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326 @param isInv flag indicating an inverse operation (boolean) |
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327 @return modified state (bytearray) |
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328 """ |
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329 state = state[:] |
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330 for i in range(4): |
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331 state = self.__shiftRow(state, i * 4, i, isInv) |
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332 return state |
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333 |
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334 def __shiftRow(self, state, statePointer, nbr, isInv): |
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335 """ |
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336 Private method to shift the bytes of a row to the left. |
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337 |
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338 @param state state to be worked on (bytearray) |
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339 @param statePointer index into the state (integer) |
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340 @param nbr number of positions to shift (integer) |
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341 @param isInv flag indicating an inverse operation (boolean) |
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342 @return modified state (bytearray) |
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343 """ |
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344 state = state[:] |
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345 for _ in range(nbr): |
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346 if isInv: |
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347 state[statePointer:statePointer + 4] = ( |
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348 state[statePointer + 3:statePointer + 4] + |
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349 state[statePointer:statePointer + 3] |
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350 ) |
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351 else: |
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352 state[statePointer:statePointer + 4] = ( |
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353 state[statePointer + 1:statePointer + 4] + |
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354 state[statePointer:statePointer + 1] |
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355 ) |
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356 return state |
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357 |
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358 def __mixColumns(self, state, isInv): |
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359 """ |
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360 Private method to perform a galois multiplication of the 4x4 matrix. |
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361 |
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362 @param state state to be worked on (bytearray) |
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363 @param isInv flag indicating an inverse operation (boolean) |
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364 @return modified state (bytearray) |
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365 """ |
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366 state = state[:] |
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367 # iterate over the 4 columns |
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368 for i in range(4): |
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369 # construct one column by slicing over the 4 rows |
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370 column = state[i:i + 16:4] |
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371 # apply the __mixColumn on one column |
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372 column = self.__mixColumn(column, isInv) |
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373 # put the values back into the state |
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374 state[i:i + 16:4] = column |
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375 |
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376 return state |
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377 |
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378 # galois multiplication of 1 column of the 4x4 matrix |
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379 def __mixColumn(self, column, isInv): |
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380 """ |
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381 Private method to perform a galois multiplication of 1 column the |
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382 4x4 matrix. |
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383 |
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384 @param column column to be worked on (bytearray) |
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385 @param isInv flag indicating an inverse operation (boolean) |
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386 @return modified column (bytearray) |
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387 """ |
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388 column = column[:] |
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389 mult = [14, 9, 13, 11] if isInv else [2, 1, 1, 3] |
|
390 cpy = column[:] |
|
391 g = self.__galois_multiplication |
|
392 |
|
393 column[0] = ( |
|
394 g(cpy[0], mult[0]) ^ g(cpy[3], mult[1]) ^ |
|
395 g(cpy[2], mult[2]) ^ g(cpy[1], mult[3]) |
|
396 ) |
|
397 column[1] = ( |
|
398 g(cpy[1], mult[0]) ^ g(cpy[0], mult[1]) ^ |
|
399 g(cpy[3], mult[2]) ^ g(cpy[2], mult[3]) |
|
400 ) |
|
401 column[2] = ( |
|
402 g(cpy[2], mult[0]) ^ g(cpy[1], mult[1]) ^ |
|
403 g(cpy[0], mult[2]) ^ g(cpy[3], mult[3]) |
|
404 ) |
|
405 column[3] = ( |
|
406 g(cpy[3], mult[0]) ^ g(cpy[2], mult[1]) ^ |
|
407 g(cpy[1], mult[2]) ^ g(cpy[0], mult[3]) |
|
408 ) |
|
409 return column |
|
410 |
|
411 def __aes_round(self, state, roundKey): |
|
412 """ |
|
413 Private method to apply the 4 operations of the forward round in |
|
414 sequence. |
|
415 |
|
416 @param state state to be worked on (bytearray) |
|
417 @param roundKey round key to be used (bytearray) |
|
418 @return modified state (bytearray) |
|
419 """ |
|
420 state = self.__subBytes(state, False) |
|
421 state = self.__shiftRows(state, False) |
|
422 state = self.__mixColumns(state, False) |
|
423 state = self.__addRoundKey(state, roundKey) |
|
424 return state |
|
425 |
|
426 def __aes_invRound(self, state, roundKey): |
|
427 """ |
|
428 Private method to apply the 4 operations of the inverse round in |
|
429 sequence. |
|
430 |
|
431 @param state state to be worked on (bytearray) |
|
432 @param roundKey round key to be used (bytearray) |
|
433 @return modified state (bytearray) |
|
434 """ |
|
435 state = self.__shiftRows(state, True) |
|
436 state = self.__subBytes(state, True) |
|
437 state = self.__addRoundKey(state, roundKey) |
|
438 state = self.__mixColumns(state, True) |
|
439 return state |
|
440 |
|
441 def __aes_main(self, state, expandedKey, nbrRounds): |
|
442 """ |
|
443 Private method to do the AES encryption for one round. |
|
444 |
|
445 Perform the initial operations, the standard round, and the |
|
446 final operations of the forward AES, creating a round key for |
|
447 each round. |
|
448 |
|
449 @param state state to be worked on (bytearray) |
|
450 @param expandedKey expanded key to be used (bytearray) |
|
451 @param nbrRounds number of rounds to be done (integer) |
|
452 @return modified state (bytearray) |
|
453 """ |
|
454 state = self.__addRoundKey( |
|
455 state, self.__createRoundKey(expandedKey, 0)) |
|
456 i = 1 |
|
457 while i < nbrRounds: |
|
458 state = self.__aes_round( |
|
459 state, self.__createRoundKey(expandedKey, 16 * i)) |
|
460 i += 1 |
|
461 state = self.__subBytes(state, False) |
|
462 state = self.__shiftRows(state, False) |
|
463 state = self.__addRoundKey( |
|
464 state, self.__createRoundKey(expandedKey, 16 * nbrRounds)) |
|
465 return state |
|
466 |
|
467 def __aes_invMain(self, state, expandedKey, nbrRounds): |
|
468 """ |
|
469 Private method to do the inverse AES encryption for one round. |
|
470 |
|
471 Perform the initial operations, the standard round, and the |
|
472 final operations of the inverse AES, creating a round key for |
|
473 each round. |
|
474 |
|
475 @param state state to be worked on (bytearray) |
|
476 @param expandedKey expanded key to be used (bytearray) |
|
477 @param nbrRounds number of rounds to be done (integer) |
|
478 @return modified state (bytearray) |
|
479 """ |
|
480 state = self.__addRoundKey( |
|
481 state, self.__createRoundKey(expandedKey, 16 * nbrRounds)) |
|
482 i = nbrRounds - 1 |
|
483 while i > 0: |
|
484 state = self.__aes_invRound( |
|
485 state, self.__createRoundKey(expandedKey, 16 * i)) |
|
486 i -= 1 |
|
487 state = self.__shiftRows(state, True) |
|
488 state = self.__subBytes(state, True) |
|
489 state = self.__addRoundKey( |
|
490 state, self.__createRoundKey(expandedKey, 0)) |
|
491 return state |
|
492 |
|
493 def encrypt(self, iput, key, size): |
|
494 """ |
|
495 Public method to encrypt a 128 bit input block against the given key |
|
496 of size specified. |
|
497 |
|
498 @param iput input data (bytearray) |
|
499 @param key key to be used (bytes or bytearray) |
|
500 @param size key size (16, 24 or 32) |
|
501 @return encrypted data (bytes) |
|
502 @exception ValueError key size is invalid |
|
503 """ |
|
504 if size not in self.KeySize.values(): |
|
505 raise ValueError("Wrong key size given ({0}).".format(size)) |
|
506 |
|
507 output = bytearray(16) |
|
508 # the number of rounds |
|
509 nbrRounds = 0 |
|
510 # the 128 bit block to encode |
|
511 block = bytearray(16) |
|
512 # set the number of rounds |
|
513 if size == self.KeySize["SIZE_128"]: |
|
514 nbrRounds = 10 |
|
515 elif size == self.KeySize["SIZE_192"]: |
|
516 nbrRounds = 12 |
|
517 else: |
|
518 nbrRounds = 14 |
|
519 |
|
520 # the expanded keySize |
|
521 expandedKeySize = 16 * (nbrRounds + 1) |
|
522 |
|
523 # Set the block values, for the block: |
|
524 # a0,0 a0,1 a0,2 a0,3 |
|
525 # a1,0 a1,1 a1,2 a1,3 |
|
526 # a2,0 a2,1 a2,2 a2,3 |
|
527 # a3,0 a3,1 a3,2 a3,3 |
|
528 # the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3 |
|
529 # |
|
530 # iterate over the columns |
|
531 for i in range(4): |
|
532 # iterate over the rows |
|
533 for j in range(4): |
|
534 block[i + j * 4] = iput[i * 4 + j] |
|
535 |
|
536 # expand the key into an 176, 208, 240 bytes key |
|
537 # the expanded key |
|
538 expandedKey = self.__expandKey(key, size, expandedKeySize) |
|
539 |
|
540 # encrypt the block using the expandedKey |
|
541 block = self.__aes_main(block, expandedKey, nbrRounds) |
|
542 |
|
543 # unmap the block again into the output |
|
544 for kk in range(4): |
|
545 # iterate over the rows |
|
546 for ll in range(4): |
|
547 output[kk * 4 + ll] = block[kk + ll * 4] |
|
548 return bytes(output) |
|
549 |
|
550 # decrypts a 128 bit input block against the given key of size specified |
|
551 def decrypt(self, iput, key, size): |
|
552 """ |
|
553 Public method to decrypt a 128 bit input block against the given key |
|
554 of size specified. |
|
555 |
|
556 @param iput input data (bytearray) |
|
557 @param key key to be used (bytes or bytearray) |
|
558 @param size key size (16, 24 or 32) |
|
559 @return decrypted data (bytes) |
|
560 @exception ValueError key size is invalid |
|
561 """ |
|
562 if size not in self.KeySize.values(): |
|
563 raise ValueError("Wrong key size given ({0}).".format(size)) |
|
564 |
|
565 output = bytearray(16) |
|
566 # the number of rounds |
|
567 nbrRounds = 0 |
|
568 # the 128 bit block to decode |
|
569 block = bytearray(16) |
|
570 # set the number of rounds |
|
571 |
|
572 if size == self.KeySize["SIZE_128"]: |
|
573 nbrRounds = 10 |
|
574 elif size == self.KeySize["SIZE_192"]: |
|
575 nbrRounds = 12 |
|
576 else: |
|
577 nbrRounds = 14 |
|
578 |
|
579 # the expanded keySize |
|
580 expandedKeySize = 16 * (nbrRounds + 1) |
|
581 |
|
582 # Set the block values, for the block: |
|
583 # a0,0 a0,1 a0,2 a0,3 |
|
584 # a1,0 a1,1 a1,2 a1,3 |
|
585 # a2,0 a2,1 a2,2 a2,3 |
|
586 # a3,0 a3,1 a3,2 a3,3 |
|
587 # the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3 |
|
588 |
|
589 # iterate over the columns |
|
590 for i in range(4): |
|
591 # iterate over the rows |
|
592 for j in range(4): |
|
593 block[i + j * 4] = iput[i * 4 + j] |
|
594 # expand the key into an 176, 208, 240 bytes key |
|
595 expandedKey = self.__expandKey(key, size, expandedKeySize) |
|
596 # decrypt the block using the expandedKey |
|
597 block = self.__aes_invMain(block, expandedKey, nbrRounds) |
|
598 # unmap the block again into the output |
|
599 for kk in range(4): |
|
600 # iterate over the rows |
|
601 for ll in range(4): |
|
602 output[kk * 4 + ll] = block[kk + ll * 4] |
|
603 return output |
|
604 |
|
605 |
|
606 class AESModeOfOperation: |
|
607 """ |
|
608 Class implementing the different AES mode of operations. |
|
609 """ |
|
610 aes = AES() |
|
611 |
|
612 # structure of supported modes of operation |
|
613 ModeOfOperation = { |
|
614 "OFB": 0, |
|
615 "CFB": 1, |
|
616 "CBC": 2, |
|
617 } |
|
618 |
|
619 def __extractBytes(self, inputData, start, end, mode): |
|
620 """ |
|
621 Private method to extract a range of bytes from the input. |
|
622 |
|
623 @param inputData input data (bytes) |
|
624 @param start start index (integer) |
|
625 @param end end index (integer) |
|
626 @param mode mode of operation (0, 1, 2) |
|
627 @return extracted bytes (bytearray) |
|
628 """ |
|
629 if end - start > 16: |
|
630 end = start + 16 |
|
631 ar = (bytearray(16) if mode == self.ModeOfOperation["CBC"] |
|
632 else bytearray()) |
|
633 |
|
634 i = start |
|
635 j = 0 |
|
636 while len(ar) < end - start: |
|
637 ar.append(0) |
|
638 while i < end: |
|
639 ar[j] = inputData[i] |
|
640 j += 1 |
|
641 i += 1 |
|
642 return ar |
|
643 |
|
644 def encrypt(self, inputData, mode, key, size, IV): |
|
645 """ |
|
646 Public method to perform the encryption operation. |
|
647 |
|
648 @param inputData data to be encrypted (bytes) |
|
649 @param mode mode of operation (0, 1 or 2) |
|
650 @param key key to be used (bytes) |
|
651 @param size length of the key (16, 24 or 32) |
|
652 @param IV initialisation vector (bytearray) |
|
653 @return tuple with mode of operation, length of the input data and |
|
654 the encrypted data (integer, integer, bytes) |
|
655 @exception ValueError key size is invalid or decrypted data is invalid |
|
656 """ |
|
657 if len(key) % size: |
|
658 raise ValueError("Illegal size ({0}) for key '{1}'.".format( |
|
659 size, key)) |
|
660 if len(IV) % 16: |
|
661 raise ValueError("IV is not a multiple of 16.") |
|
662 # the AES input/output |
|
663 iput = bytearray(16) |
|
664 output = bytearray() |
|
665 ciphertext = bytearray(16) |
|
666 # the output cipher string |
|
667 cipherOut = bytearray() |
|
668 # char firstRound |
|
669 firstRound = True |
|
670 if inputData: |
|
671 for j in range(int(math.ceil(float(len(inputData)) / 16))): |
|
672 start = j * 16 |
|
673 end = j * 16 + 16 |
|
674 if end > len(inputData): |
|
675 end = len(inputData) |
|
676 plaintext = self.__extractBytes(inputData, start, end, mode) |
|
677 if mode == self.ModeOfOperation["CFB"]: |
|
678 if firstRound: |
|
679 output = self.aes.encrypt(IV, key, size) |
|
680 firstRound = False |
|
681 else: |
|
682 output = self.aes.encrypt(iput, key, size) |
|
683 for i in range(16): |
|
684 if len(plaintext) - 1 < i: |
|
685 ciphertext[i] = 0 ^ output[i] |
|
686 elif len(output) - 1 < i: |
|
687 ciphertext[i] = plaintext[i] ^ 0 |
|
688 elif len(plaintext) - 1 < i and len(output) < i: |
|
689 ciphertext[i] = 0 ^ 0 |
|
690 else: |
|
691 ciphertext[i] = plaintext[i] ^ output[i] |
|
692 for k in range(end - start): |
|
693 cipherOut.append(ciphertext[k]) |
|
694 iput = ciphertext |
|
695 elif mode == self.ModeOfOperation["OFB"]: |
|
696 if firstRound: |
|
697 output = self.aes.encrypt(IV, key, size) |
|
698 firstRound = False |
|
699 else: |
|
700 output = self.aes.encrypt(iput, key, size) |
|
701 for i in range(16): |
|
702 if len(plaintext) - 1 < i: |
|
703 ciphertext[i] = 0 ^ output[i] |
|
704 elif len(output) - 1 < i: |
|
705 ciphertext[i] = plaintext[i] ^ 0 |
|
706 elif len(plaintext) - 1 < i and len(output) < i: |
|
707 ciphertext[i] = 0 ^ 0 |
|
708 else: |
|
709 ciphertext[i] = plaintext[i] ^ output[i] |
|
710 for k in range(end - start): |
|
711 cipherOut.append(ciphertext[k]) |
|
712 iput = output |
|
713 elif mode == self.ModeOfOperation["CBC"]: |
|
714 for i in range(16): |
|
715 if firstRound: |
|
716 iput[i] = plaintext[i] ^ IV[i] |
|
717 else: |
|
718 iput[i] = plaintext[i] ^ ciphertext[i] |
|
719 firstRound = False |
|
720 ciphertext = self.aes.encrypt(iput, key, size) |
|
721 # always 16 bytes because of the padding for CBC |
|
722 for k in range(16): |
|
723 cipherOut.append(ciphertext[k]) |
|
724 return mode, len(inputData), bytes(cipherOut) |
|
725 |
|
726 # Mode of Operation Decryption |
|
727 # cipherIn - Encrypted String |
|
728 # originalsize - The unencrypted string length - required for CBC |
|
729 # mode - mode of type modeOfOperation |
|
730 # key - a number array of the bit length size |
|
731 # size - the bit length of the key |
|
732 # IV - the 128 bit number array Initilization Vector |
|
733 def decrypt(self, cipherIn, originalsize, mode, key, size, IV): |
|
734 """ |
|
735 Public method to perform the decryption operation. |
|
736 |
|
737 @param cipherIn data to be decrypted (bytes) |
|
738 @param originalsize unencrypted string length (required for CBC) |
|
739 (integer) |
|
740 @param mode mode of operation (0, 1 or 2) |
|
741 @param key key to be used (bytes) |
|
742 @param size length of the key (16, 24 or 32) |
|
743 @param IV initialisation vector (bytearray) |
|
744 @return decrypted data (bytes) |
|
745 @exception ValueError key size is invalid or decrypted data is invalid |
|
746 """ |
|
747 if len(key) % size: |
|
748 raise ValueError("Illegal size ({0}) for key '{1}'.".format( |
|
749 size, key)) |
|
750 if len(IV) % 16: |
|
751 raise ValueError("IV is not a multiple of 16.") |
|
752 # the AES input/output |
|
753 ciphertext = bytearray() |
|
754 iput = bytearray() |
|
755 output = bytearray() |
|
756 plaintext = bytearray(16) |
|
757 # the output bytes |
|
758 bytesOut = bytearray() |
|
759 # char firstRound |
|
760 firstRound = True |
|
761 if cipherIn is not None: |
|
762 for j in range(int(math.ceil(float(len(cipherIn)) / 16))): |
|
763 start = j * 16 |
|
764 end = j * 16 + 16 |
|
765 if j * 16 + 16 > len(cipherIn): |
|
766 end = len(cipherIn) |
|
767 ciphertext = cipherIn[start:end] |
|
768 if mode == self.ModeOfOperation["CFB"]: |
|
769 if firstRound: |
|
770 output = self.aes.encrypt(IV, key, size) |
|
771 firstRound = False |
|
772 else: |
|
773 output = self.aes.encrypt(iput, key, size) |
|
774 for i in range(16): |
|
775 if len(output) - 1 < i: |
|
776 plaintext[i] = 0 ^ ciphertext[i] |
|
777 elif len(ciphertext) - 1 < i: |
|
778 plaintext[i] = output[i] ^ 0 |
|
779 elif len(output) - 1 < i and len(ciphertext) < i: |
|
780 plaintext[i] = 0 ^ 0 |
|
781 else: |
|
782 plaintext[i] = output[i] ^ ciphertext[i] |
|
783 for k in range(end - start): |
|
784 bytesOut.append(plaintext[k]) |
|
785 iput = ciphertext |
|
786 elif mode == self.ModeOfOperation["OFB"]: |
|
787 if firstRound: |
|
788 output = self.aes.encrypt(IV, key, size) |
|
789 firstRound = False |
|
790 else: |
|
791 output = self.aes.encrypt(iput, key, size) |
|
792 for i in range(16): |
|
793 if len(output) - 1 < i: |
|
794 plaintext[i] = 0 ^ ciphertext[i] |
|
795 elif len(ciphertext) - 1 < i: |
|
796 plaintext[i] = output[i] ^ 0 |
|
797 elif len(output) - 1 < i and len(ciphertext) < i: |
|
798 plaintext[i] = 0 ^ 0 |
|
799 else: |
|
800 plaintext[i] = output[i] ^ ciphertext[i] |
|
801 for k in range(end - start): |
|
802 bytesOut.append(plaintext[k]) |
|
803 iput = output |
|
804 elif mode == self.ModeOfOperation["CBC"]: |
|
805 output = self.aes.decrypt(ciphertext, key, size) |
|
806 for i in range(16): |
|
807 if firstRound: |
|
808 plaintext[i] = IV[i] ^ output[i] |
|
809 else: |
|
810 plaintext[i] = iput[i] ^ output[i] |
|
811 firstRound = False |
|
812 if originalsize is not None and originalsize < end: |
|
813 for k in range(originalsize - start): |
|
814 bytesOut.append(plaintext[k]) |
|
815 else: |
|
816 for k in range(end - start): |
|
817 bytesOut.append(plaintext[k]) |
|
818 iput = ciphertext |
|
819 return bytes(bytesOut) |
|
820 |
|
821 |
|
822 def encryptData(key, data, mode=AESModeOfOperation.ModeOfOperation["CBC"]): |
|
823 """ |
|
824 Module function to encrypt the given data with the given key. |
|
825 |
|
826 @param key key to be used for encryption (bytes) |
|
827 @param data data to be encrypted (bytes) |
|
828 @param mode mode of operations (0, 1 or 2) |
|
829 @return encrypted data prepended with the initialization vector (bytes) |
|
830 @exception ValueError raised to indicate an invalid key size |
|
831 """ |
|
832 key = bytearray(key) |
|
833 if mode == AESModeOfOperation.ModeOfOperation["CBC"]: |
|
834 data = append_PKCS7_padding(data) |
|
835 keysize = len(key) |
|
836 if keysize not in AES.KeySize.values(): |
|
837 raise ValueError('invalid key size: {0}'.format(keysize)) |
|
838 # create a new iv using random data |
|
839 iv = bytearray([i for i in os.urandom(16)]) |
|
840 moo = AESModeOfOperation() |
|
841 mode, length, ciph = moo.encrypt(data, mode, key, keysize, iv) |
|
842 # With padding, the original length does not need to be known. It's a bad |
|
843 # idea to store the original message length. |
|
844 # prepend the iv. |
|
845 return bytes(iv) + bytes(ciph) |
|
846 |
|
847 |
|
848 def decryptData(key, data, mode=AESModeOfOperation.ModeOfOperation["CBC"]): |
|
849 """ |
|
850 Module function to decrypt the given data with the given key. |
|
851 |
|
852 @param key key to be used for decryption (bytes) |
|
853 @param data data to be decrypted (with initialization vector prepended) |
|
854 (bytes) |
|
855 @param mode mode of operations (0, 1 or 2) |
|
856 @return decrypted data (bytes) |
|
857 @exception ValueError raised to indicate an invalid key size |
|
858 """ |
|
859 key = bytearray(key) |
|
860 keysize = len(key) |
|
861 if keysize not in AES.KeySize.values(): |
|
862 raise ValueError('invalid key size: {0}'.format(keysize)) |
|
863 # iv is first 16 bytes |
|
864 iv = bytearray(data[:16]) |
|
865 data = bytearray(data[16:]) |
|
866 moo = AESModeOfOperation() |
|
867 decr = moo.decrypt(data, None, mode, key, keysize, iv) |
|
868 if mode == AESModeOfOperation.ModeOfOperation["CBC"]: |
|
869 decr = strip_PKCS7_padding(decr) |
|
870 return bytes(decr) |