Sharing of 2 more classic PHP encryption and decryption functions_PHP Tutorial

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

The author has collected some classic PHP encryption and decryption function codes to share with you. The principle of encryption and decryption is generally to use a certain encryption and decryption algorithm, add the key to the algorithm, and finally obtain the encryption and decryption results.
1. Very powerful authcode encryption function, Discuz! Classic code (with detailed explanation):

Copy code The code is as follows:

function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) {
// Dynamic key length, the same plaintext will generate different ciphertext, relying on the dynamic key
$ckey_length = 4;
                         
// Key
$key = md5($key ? $key : $GLOBALS['discuz_auth_key']);
                         
// Key a will participate in encryption and decryption
$keya = md5(substr($key, 0, 16));
// Key b will be 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, $ckey_length):
substr(md5(microtime()), -$ckey_length)) : '';
// Keys involved in calculations
$cryptkey = $keya.md5($keya.$keyc);
$key_length = strlen($cryptkey);
// Plain text, the first 10 bits are used to save the timestamp, and the data validity is verified during decryption, and the 10 to 26 bits are used to save $keyb (key b),
//Data integrity will be verified through this key when decrypting
// If it is decoding, it will start 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(0, 255);
$rndkey = array();
// Generate keybook
for($i = 0; $i <= 255; $i++) {
           $rndkey[$i] = ord($cryptkey[$i % $key_length]);                                              }  
// Use a fixed algorithm to scramble the key book and increase randomness. It seems very complicated, but in fact it will not increase the strength of the ciphertext
for($j = $i = 0; $i < 256; $i++) {
         $j = ($j + $box[$i] + $rndkey[$i]) % 256;            $tmp = $box[$i];                                                  $box[$i] = $box[$j];                                                $box[$j] = $tmp;                                         }  
// Core encryption and decryption part
for($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;                                                          // Get the key from the key book, perform XOR, and then convert it into characters
         $result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256])); }  
If($operation == 'DECODE') {
// To verify data validity, please see the format of unencrypted plaintext
If((substr($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);                                                                                                                         return '';                                                                                                                       } else {
//Save the dynamic key in the ciphertext, which is why the same plaintext can be decrypted after producing different ciphertexts
// Because the encrypted ciphertext may contain some special characters and may be lost during the copying process, base64 encoding is used
             return $keyc.str_replace('=', '', base64_encode($result));                                                    }  
}

$string in function authcode($string, $operation, $key, $expiry): string, plaintext or ciphertext; $operation: DECODE means decryption, others means encryption; $key: secret key; $expiry : The validity period of the ciphertext.

Usage:

Copy code The code is as follows:

$str = 'abcdef';
$key = 'www.helloweba.com';
echo authcode($str,'ENCODE',$key,0); //Encryption
$str = '56f4yER1DI2WTzWMqsfPpS9hwyoJnFP2MpC8SOhRrxO7BOk';
echo authcode($str,'DECODE',$key,0); //Decrypt

2. Encryption and decryption function encrypt():

Copy code The code is as follows:

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($result,8);
         }else{
             return'';
          }
}else{
           return str_replace('=','',base64_encode($result));
}
}

In function encrypt($string,$operation,$key), $string: the string that needs to be encrypted and decrypted; $operation: determine whether to encrypt or decrypt, E means encryption, D means decryption; $key: key.

Usage:

Copy code The code is as follows:

$str = 'abc';
$key = 'www.helloweba.com';
$token = encrypt($str, 'E', $key);
echo 'Encryption:'.encrypt($str, 'E', $key);
echo 'Decrypt:'.encrypt($str, 'D', $key);

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