In-depth study on UCenterAPI-PHP encryption and decryption

The encryption and decryption function in UCenterAPI, known as a classic in the php field, is also a major contribution of Kangsheng to php. it can generate dynamic ciphertext through a KEY, you can use this KEY to solve the problem.

The encryption and decryption function in the UCenter API is called a classic in the php field and is also a major contribution made by Kangsheng for php.

This function can generate dynamic ciphertext through a KEY, and then use this KEY to parse

 

 
 

  
  
 // $ String: plaintext or ciphertext
  
  
// $ Operation: DECODE indicates decryption, and others indicates encryption
  
  
// $ Key: key
  
  
// $ Expiry: ciphertext validity period
  
  
// String decryption and encryption
  
  
Function authcode ($ string, $ operation = 'Decode', $ key = '', $ expiry = 0 ){
  
  
// The length of the dynamic key. different ciphertext values are generated for the same plaintext based on the dynamic key.
  
  
$ Ckey_length = 4; // The random key length ranges from 0 to 32;
  
  
// Adding a random key can make the ciphertext irregular. even if the original text and the key are identical, the encryption results will be different each time, increasing the difficulty of cracking.
  
  
// The larger the value, the larger the ciphertext change law. The ciphertext change is equal to the power of $ ckey_length of 16.
  
  
// When this value is 0, no random key is generated
  
  
// Key
  
  
$ Key = md5 ($ key? $ Key: UC_KEY );
  
  
// Key a is used for encryption and decryption.
  
  
$ Keya = md5 (substr ($ key, 0, 16 ));
  
  
// Key B is used for data integrity verification.
  
  
$ Keyb = md5 (substr ($ key, 16, 16 ));
  
  
// Key c is used to change the generated ciphertext
  
  
$ Keyc = $ ckey_length? ($ Operation = 'decode '? Substr ($ string, 0, $ ckey_length): substr (md5 ('000000'),-$ ckey_length )):'';
  
  
// Key used for calculation
  
  
$ Cryptkey = $ keya. md5 ($ keya. $ keyc );
  
  

  
  
$ Key_length = strlen ($ cryptkey );
  
  

  
  
// Plaintext. the first 10 digits are used to save the timestamp. data validity is verified during decryption, and 10 to 26 digits are used to save $ keyb (key B). Data integrity is verified through this key during decryption.
  
  
// If it is decoded, it starts from the $ ckey_length bit, because the $ ckey_length bit before the ciphertext stores the dynamic key to ensure correct decryption.
  
  
$ String = $ operation = 'decode '? Base64_decode (substr ($ string, $ ckey_length): sprintf ('% 010d', $ expiry? $ Expiry + time (): 0). substr (md5 ($ string. $ keyb), 0, 16). $ string;
  
  
$ String_length = strlen ($ string );
  
  
$ Result = '';
  
  
$ Box = range (1, 0,255 );
  
  
$ Rndkey = array ();
  
  
// Generate a key book
  
  
For ($ I = 0; $ I <= 255; $ I ++ ){
  
  
$ Rndkey [$ I] = ord ($ cryptkey [$ I % $ key_length]);
  
  
}
  
  
// Use a fixed algorithm to disrupt the key book and increase randomness. it seems complicated. In fact, it does not increase the ciphertext strength.
  
  
For ($ j = $ I = 0; I I <256; $ I ++ ){
  
  
$ J = ($ j + $ box [$ I] + $ rndkey [$ I]) % 256;
  
  
$ Tmp = $ box [$ I];
  
  
$ Box [$ I] = $ box [$ j];
  
  
$ Box [$ j] = $ tmp;
  
  
}
  
  
// Core encryption/decryption part
  
  
For ($ a = $ j = $ I = 0; $ I <$ string_length; $ I ++ ){
  
  
$ A = ($ a + 1) % 256;
  
  
$ J = ($ j + $ box [$ a]) % 256;
  
  
$ Tmp = $ box [$ a];
  
  
$ Box [$ a] = $ box [$ j];
  
  
$ Box [$ j] = $ tmp;
  
  
// The Keys obtained from the key book are different or converted into characters.
  
  
$ Result. = chr (ord ($ string [$ I]) ^ ($ box [($ box [$ a] + $ box [$ j]) % 256]);
  
  
}
  
  
If ($ operation = 'decode '){
  
  
// Verify the data validity. see the unencrypted plaintext format.
  
  
If (substr ($ result, 0, 10) = 0 | substr ($ result, 0, 10)-time ()> 0) & substr ($ result, 10, 16) = substr (md5 (substr ($ result, 26 ). $ keyb), 0, 16 )){
  
  
Return substr ($ result, 26 );
  
  
} Else {
  
  
Return '';
  
  
}
  
  
} Else {
  
  
// Save the dynamic key in the ciphertext, which is why different ciphertext can be decrypted in the same plain text.
  
  
// Because the encrypted ciphertext may be special characters, the copying process may be lost, so it is Base64-encoded.
  
  
Return $ keyc. str_replace ('=', '', base64_encode ($ result ));
  
  
}
  
  
}
  
  
Echo authcode ('20140901', 'incode', 'jobphper ', 0 );
  
  
Echo"
";
  
  
Echo authcode ('3575ijqlncr + R3s7Aakwy1HlvDzHw5g4oKp82qhE7q5FS88 ', 'Decode', 'jobphper', 0 );
  
  
?>
 
 

 

I did not write this explanation. I have a lot on the internet and cannot find the original author.

Reprinted address http://www.dozer.cc/2011/01/ucenter-api-in-depth-3rd/