PHP encryption and decryption function example tutorial_PHP tutorial

Sharing of PHP encryption and decryption functions, one is Discuz!'s authcode encryption function (with detailed decomposition), and the other is the encrypt() function.

You need to use PHP to encrypt specific information, that is, an encrypted string is generated 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):

function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) {
// Dynamic key length, the same plaintext will generate different ciphertext, relying on dynamic encryption 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)) : '';
// 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(cryptkey) Key b),
//This key will be used to verify data integrity when decrypting
// If decoding, it will start from the $ckey_length bit, because the dynamic key is stored in the $ckey_length bit before the ciphertext. 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 % $key_length]);
}
// Use a fixed algorithm to scramble the key book and increase randomness. It seems very complicated, but in fact it is It will not increase the strength of the ciphertext
for($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($operation == 'DECODE' ) {
// Verify data validity, please see the format of unencrypted plaintext
if((substr($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 {
// Save the dynamic key in the ciphertext, which is why the same plaintext, The reason why different ciphertexts can be decrypted after producing them
// 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: key; $expiry: ciphertext validity period.
Usage:

$str = 'abcdef';
$key = 'www.jbxue.com';
echo authcode($str,'ENCODE',$key,0); //Encryption
$ str = '56f4yER1DI2WTzWMqsfPpS9hwyoJnFP2MpC8SOhRrxO7BOk';
echo authcode($str,'DECODE',$key,0); //Decryption
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($result,8);
}else{
return'';
} // www.jbxue.com
}else{
return str_replace('=','',base64_encode($result));
}
}
函数encrypt($string,$operation,$key)中$string：需要加密解密的字符串；$operation：判断是加密还是解密，E表示加密，D表示解密；$key：密匙。
用法：

$str = 'abc';
$key = 'www.jbxue.com';
$token = encrypt($str, 'E', $key);
echo '加密:'.encrypt($str, 'E', $key);
echo '解密：'.encrypt($str, 'D', $key);