Conditions | 13 |
Paths | 273 |
Total Lines | 74 |
Code Lines | 39 |
Lines | 74 |
Ratio | 100 % |
Changes | 0 |
Small methods make your code easier to understand, in particular if combined with a good name. Besides, if your method is small, finding a good name is usually much easier.
For example, if you find yourself adding comments to a method's body, this is usually a good sign to extract the commented part to a new method, and use the comment as a starting point when coming up with a good name for this new method.
Commonly applied refactorings include:
If many parameters/temporary variables are present:
1 | <?php |
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21 | public static function encrypt($plaintext, $password, $nBits) |
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22 | { |
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23 | $blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES |
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24 | if (!($nBits == 128 || $nBits == 192 || $nBits == 256)) { |
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25 | return ''; |
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26 | } |
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27 | // standard allows 128/192/256 bit keys |
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28 | // note PHP (5) gives us plaintext and password in UTF8 encoding! |
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29 | |||
30 | // use AES itself to encrypt password to get cipher key (using plain password as source for |
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31 | // key expansion) - gives us well encrypted key |
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32 | $nBytes = $nBits / 8; // no bytes in key |
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33 | $pwBytes = array(); |
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34 | for ($i = 0; $i < $nBytes; $i++) { |
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35 | $pwBytes[$i] = ord(substr($password, $i, 1)) & 0xff; |
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36 | } |
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37 | $key = Aes::cipher($pwBytes, Aes::keyExpansion($pwBytes)); |
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38 | $key = array_merge($key, array_slice($key, 0, $nBytes - 16)); // expand key to 16/24/32 bytes long |
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39 | |||
40 | // initialise counter block (NIST SP800-38A §B.2): millisecond time-stamp for nonce in |
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41 | // 1st 8 bytes, block counter in 2nd 8 bytes |
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42 | $counterBlock = array(); |
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43 | $nonce = floor(microtime(true) * 1000); // timestamp: milliseconds since 1-Jan-1970 |
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44 | $nonceSec = floor($nonce / 1000); |
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45 | $nonceMs = $nonce % 1000; |
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46 | // encode nonce with seconds in 1st 4 bytes, and (repeated) ms part filling 2nd 4 bytes |
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47 | for ($i = 0; $i < 4; $i++) { |
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48 | $counterBlock[$i] = self::urs($nonceSec, $i * 8) & 0xff; |
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49 | } |
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50 | for ($i = 0; $i < 4; $i++) { |
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51 | $counterBlock[$i + 4] = $nonceMs & 0xff; |
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52 | } |
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53 | // and convert it to a string to go on the front of the ciphertext |
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54 | $ctrTxt = ''; |
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55 | for ($i = 0; $i < 8; $i++) { |
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56 | $ctrTxt .= chr($counterBlock[$i]); |
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57 | } |
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58 | |||
59 | // generate key schedule - an expansion of the key into distinct Key Rounds for each round |
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60 | $keySchedule = Aes::keyExpansion($key); |
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61 | //print_r($keySchedule); |
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62 | |||
63 | $blockCount = ceil(strlen($plaintext) / $blockSize); |
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64 | $ciphertxt = array(); // ciphertext as array of strings |
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65 | |||
66 | for ($b = 0; $b < $blockCount; $b++) { |
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67 | // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes) |
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68 | // done in two stages for 32-bit ops: using two words allows us to go past 2^32 blocks (68GB) |
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69 | for ($c = 0; $c < 4; $c++) { |
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70 | $counterBlock[15 - $c] = self::urs($b, $c * 8) & 0xff; |
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71 | } |
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72 | for ($c = 0; $c < 4; $c++) { |
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73 | $counterBlock[15 - $c - 4] = self::urs($b / 0x100000000, $c * 8); |
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74 | } |
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75 | |||
76 | $cipherCntr = Aes::cipher($counterBlock, $keySchedule); // -- encrypt counter block -- |
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77 | |||
78 | // block size is reduced on final block |
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79 | $blockLength = $b < $blockCount - 1 ? $blockSize : (strlen($plaintext) - 1) % $blockSize + 1; |
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80 | $cipherByte = array(); |
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81 | |||
82 | for ($i = 0; $i < $blockLength; $i++) { // -- xor plaintext with ciphered counter byte-by-byte -- |
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83 | $cipherByte[$i] = $cipherCntr[$i] ^ ord(substr($plaintext, $b * $blockSize + $i, 1)); |
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84 | $cipherByte[$i] = chr($cipherByte[$i]); |
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85 | } |
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86 | $ciphertxt[$b] = implode('', $cipherByte); // escape troublesome characters in ciphertext |
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87 | } |
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88 | |||
89 | // implode is more efficient than repeated string concatenation |
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90 | $ciphertext = $ctrTxt.implode('', $ciphertxt); |
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91 | $ciphertext = base64_encode($ciphertext); |
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92 | |||
93 | return $ciphertext; |
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94 | } |
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95 | |||
192 |
Duplicated code is one of the most pungent code smells. If you need to duplicate the same code in three or more different places, we strongly encourage you to look into extracting the code into a single class or operation.
You can also find more detailed suggestions in the “Code” section of your repository.