PHP Encryption decryption string Rollup _php tips

Sometimes in the project we need to use PHP to encrypt specific information, that is, through the encryption algorithm to generate an encrypted string, the encrypted string can be decrypted by decryption algorithm to facilitate the process of decryption information processing.
The most common applications are in user login and some API data exchange scenarios.

The author contains some of the more classic PHP encryption and decryption function code, to share with you. Encryption and decryption principle is generally through a certain encryption and decryption algorithm, the key into the algorithm, the end of the encryption and decryption results.

1, very authcode encryption function, discuz! Classic code (with detailed):

function Authcode ($string, $operation = ' DECODE ', $key = ', $expiry = 0) {//dynamic key length, the same plaintext will generate different ciphertext is dependent on the dynamic key $ckey _  
    
  length = 4;  
    
  Key $key = MD5 ($key $key: $GLOBALS [' Discuz_auth_key ']);  
  Key A will participate in the encryption and decryption $keya = MD5 (substr ($key, 0, 16));  
  Key B is used to do data integrity validation $keyb = MD5 (substr ($key, 16, 16)); Key C used to change the generated ciphertext $KEYC = $ckey _length?  
  ($operation = = ' DECODE ' substr ($string, 0, $ckey _length): substr (MD5 (Microtime ()),-$ckey _length)): ";  
  The key $cryptkey = $keya. MD5 ($keya. $KEYC) that participate in the operation;  
  $key _length = strlen ($cryptkey); PlainText, the first 10 bits to save the timestamp, verify the validity of the data when decrypting, 10 to 26 bits to save the $KEYB (key B),//decryption will verify the data integrity through this key///If it is decoded, it will start from the first $ckey_length, because the ciphertext before $ckey_ The length bit holds the dynamic key to ensure the decryption is correct $string = $operation = = ' DECODE '? Base64_decode (substr ($string, $ckey _length)): sprintf ('%010d ', $expiry? $expiry + Time (): 0). substr (MD5 ($string. $keyb  
  , 0). $string;  
  $string _length = strlen ($string);  
  $result = ';  
  $box = Range (0, 255); $rndkey = array();  
  Generate the key book for ($i = 0; $i <= 255 $i + +) {$rndkey [$i] = Ord ($cryptkey [$i% $key _length]); //using fixed algorithm to disrupt the key book, increase randomness, it seems very complex, in fact, will not increase the intensity of the ciphertext for ($j = $i = 0; $i < 256 $i + +) {$j = ($j + $box [$i] + $rn  
    dkey[$i])% 256;  
    $tmp = $box [$i];  
    $box [$i] = $box [$j];  
  $box [$j] = $tmp;  
    }//Core decryption part for ($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 key is derived from the key book, and then converted to the character $result. = Chr (ord ($string [$i]) ^ ($box [($box [$a] + $box [$j]) (% 256])); } if ($operation = = ' DECODE ') {//Validate data validity, see unencrypted plaintext format if (substr ($result, 0,) = 0 | | substr ($result, 0, -time () > 0) && substr ($result) = = substr (MD5 (substr ($result,). $keyb), 0) {retur  
    n substr ($result, 26);  
    else {return '; } else {//Keep the dynamic key in the ciphertext, which is why the sameClear text, production of different ciphertext can decrypt the reason//because the encrypted ciphertext may be some special characters, the copy process may be lost, so use base64 code return $KEYC. Str_replace (' = ', ', Base64_encode ($r  
  Esult)); 
 }  
}

$string in function Authcode ($string, $operation, $key, $expiry): string, plaintext, or ciphertext; $operation: decode means decryption, other means encryption; $key: Key; $ Expiry: The validity of redaction.
Usage:

$str = ' abcdef '; 
$key = ' www.helloweba.com '; 
Echo Authcode ($str, ' ENCODE ', $key, 0); Encryption 
$str = ' 56f4yer1di2wtzwmqsfpps9hwyojnfp2mpc8sohrrxo7bok '; 
Echo Authcode ($str, ' DECODE ', $key, 0); Decrypt 

2, add the decryption function encrypt ():

 function Encrypt ($string, $operation, $key = ') {$key =md5 ($key); 
   $key _length=strlen ($key); 
  $string = $operation = = ' D ' Base64_decode ($string): substr (MD5 ($string. $key), 0,8). $string; 
  $string _length=strlen ($string); 
  $rndkey = $box =array (); 
  $result = '; 
    For ($i =0 $i <=255; $i + +) {$rndkey [$i]=ord ($key [$i% $key _length]); 
  $box [$i]= $i; 
    for ($j = $i =0; $i <256; $i + +) {$j = ($j + $box [$i]+ $rndkey [$i])%256; 
    $tmp = $box [$i]; 
    $box [$i]= $box [$j]; 
  $box [$j]= $tmp; 
    for ($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; 
  $result. =CHR (Ord ($string [$i]) ^ ($box [($box [$a]+ $box [$j])%256]); } if ($operation = = = ' D ') {if (substr ($result, 0,8) ==substr (MD5 (substr ($result, 8). $key), 0,8)) {return substr ($res 
    ult,8); 
    }else{return "; 
  }else{return str_replace (' = ', ', Base64_encode ($result)); } 
} 

function Encrypt ($string, $operation, $key) in $string: Need to encrypt the decrypted string, $operation: The judge is encrypted or decrypted, E is encrypted, d is decryption; $key: Key.
Usage:

$STR = ' abc '; 
$key = ' www.helloweba.com '; 
$token = Encrypt ($str, ' E ', $key); 
Echo ' encrypt: '. Encrypt ($str, ' E ', $key); 

The above mentioned is the entire content of this article, I hope you can enjoy.