Analysis of the specific usage of PHP encryption and decryption function authcode_PHP tutorial

The specific example code of PHP encryption and decryption function authcode is as follows:

1. // Parameter explanation
2. // $string: plaintext or ciphertext
3. // $operation: DECODE means decryption, others means encryption
4. // $key: Key
5. // $expiry: Ciphertext validity period
6. function authcode($string, $operation =
   'DECODE', $key = '', $expiry = 0) {
7. // Dynamic key length, the same plaintext will generate different ciphertext, relying on the dynamic key
8. $ckey_length = 4;
9. // Key
10. $key = md5($key ? $key : $GLOBALS['discuz_auth_key']);
11. // Key a will participate in encryption and decryption
12. $ keya = md5(substr($key, 0, 16));
13. // key b Will be used for data integrity verification
14. $keyb = md5(substr ($key, 16, 16));
15. // Key c is used to change the generated ciphertext
16. $ keyc = $ckey_length ? ($operation == 'DECODE'
    ? substr($string, 0, $ckey_length): substr (md5
    (microtime()), -$ckey_length)) : '';
17. //The key used by the PHP encryption and decryption function authcode to participate in the operation
18. $cryptkey = $keya.md5($keya.$keyc);
19. $key_length = strlen($cryptkey);
20. // Plain text, the first 10 bits are used to save Timestamp, verify data validity when decrypting.
    10 to 26 bits are used to save $keyb (key b). Data integrity will be verified through this key during decryption.
21. // If it is decoding, it will start from the $ckey_length bit, because the $ckey_
    length bit before the ciphertext saves the dynamic key to ensure correct decryption
22. $string = $operation == 'DECODE' ? base64_decode(substr
    ($string, $ckey_length)) : sprintf( '%010d', $expiry ?
    $expiry + time() : 0).substr(md5($string.$keyb), 0, 16).$string;
23. $string_length = strlen($string);
24. $result = '';
(0, 255); 🎜>();
25. //PHP encryption and decryption function authcode generates key book for($i
=
26. 0; $i <= 255; $i++) {
$rndkey[$i] = ord($cryptkey[$i % $key_length]);
}
28. //Using a fixed algorithm to scramble the key book and increase randomness seems very complicated. In fact, it will not increase the strength of the ciphertext for( $j = $i
29. = 0
30. ; $i <
31. 
    256
; $i++) {
32. $j = ($j + $box[$i] + $rndkey[$i]) % 256; $tmp = $box[$i]; $box[$i] = $box[$j];
$box [$j] = $tmp;
33. }
//PHP encryption and decryption function authcode core encryption and decryption part
34. for($a
= $
35. j
= $
36. i
=
37. 0
; $i
38. <
$string_length; $i++) {
39. $a = ($a + 1) % 256; $j = ($j + $box[$a]) % 256; $tmp
= $box[$a] ;
40. $box[$a] = $box[$j];
$box[$j] = $tmp;
41. // PHP encryption and decryption function authcode gets the key from the key book, performs XOR, and then converts it into characters
$result
42. .= chr
(ord($string[$i]) ^ (
43. $box[($box[$a] + $box[$j]) % 256]));
44. }
45. if($operation
46. == 'DECODE') { // substr($result, 0, 10) == 0 Verify data validity // substr($result, 0, 10) - time()
    >
0 Verify data validity
// substr($result, 10, 16) == substr(md5(substr
48. ($result, 26).$keyb), 0, 16) Verify data integrity // Verify data validity, please see the format of unencrypted plaintext
49. if((substr($result, 0, 10) == 0 || substr( $result, 0, 10) - time()
>
50. 0) && substr($result, 10, 16) == substr(md5(substr($result, 26).$keyb), 0, 16)) {
51. return substr($result, 26);
52. } else {
53. return '';
54. }
55. } else {
56. //PHP encryption and decryption function authcode saves the dynamic key in the ciphertext, which is why the same plaintext can be decrypted after
    producing different ciphertexts
57. // Because the encrypted ciphertext may contain some special characters,
    may be lost during the copying process, so base64 encoding is used
58. return $ keyc.str_replace('=', '',
    base64_encode($result));
59. }
60. }

The above code is the specific usage of PHP encryption and decryption function authcode. I hope you can initially grasp the meaning of this function through the content introduced in this article.

http://www.bkjia.com/PHPjc/446263.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/446263.htmlTechArticleThe specific example code of PHP encryption and decryption function authcode is as follows: //Parameter explanation//$string: plain text or cipher text //$operation: DECODE means decryption, others means encryption //$key: key //$expir...