Share 2 classic PHP encryption and decryption functions

This article mainly introduces the sharing of two more classic PHP encryption and decryption functions, one is Discuz!'s authcode encryption function (with detailed decomposition), and the other is the encrypt() function, both of which are relatively classic. Friends in need can refer to it

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, so that the program can 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):

 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)) : '';

 // The key involved in the operation

 $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 10 to 26 bits are used to save $keyb (key b),

 //This key will be used to verify data integrity when decrypting

 // If it is decoding, it will start from the $ckey_length bit, because the $ckey_length bit before the ciphertext saves the dynamic secret key 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 key book

 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);

 } else {

 return '';

 }

 } else {

 // Change the dynamic The key is stored 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, it is encoded with base64

 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: encryption key; $expiry: password Document validity period.

Usage:

 $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():

  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:

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

Encryption and decryption, PHP