2 more classic PHP cryptographic decryption function Sharing _php Tutorial

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 the decryption algorithm, so that the program to process the decrypted information.
The most common applications are in user login and some API data exchange scenarios.

I have included some of the more classic PHP encryption and decryption function code, share to everyone. Encryption and decryption principle is generally through a certain encryption and decryption algorithm, the key is added to the algorithm, and finally get the encryption and decryption results.
1, the very force of the authcode cryptographic function, discuz! Classic code (with detailed):
Copy CodeThe code is as follows:
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;

Secret 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 to participate in the operation
$cryptkey = $keya. MD5 ($keya. $KEYC);
$key _length = strlen ($cryptkey);
PlainText, the first 10 bits are used to hold the timestamp, the validation data is decrypted when the validity, 10 to 26 bits to save $keyb (key B),
Data integrity is verified by this key during decryption
If it is decoded, it will start from the $ckey_length bit, because the $ckey_length bit in the ciphertext saves 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);
$rndkey = Array ();
Generate key Book
for ($i = 0; $i <= 255; $i + +) {
$rndkey [$i] = Ord ($cryptkey [$i% $key _length]);
}
Using a fixed algorithm to disrupt the key book, to increase randomness, seems very complex, in fact, does not increase the intensity of ciphertext
for ($j = $i = 0; $i < $i + +) {
$j = ($j + $box [$i] + $rndkey [$i])% 256;
$tmp = $box [$i];
$box [$i] = $box [$j];
$box [$j] = $tmp;
}
Core encryption and Decryption section
for ($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;
To derive a key from the key book, and then turn it into a character
$result. = Chr (ord ($string [$i]) ^ ($box [($box [$a] + $box [$j])% 256]));
}
if ($operation = = ' DECODE ') {
To verify data validation, see the format of unencrypted plaintext
if (substr ($result, 0, ten) = = 0 | | substr ($result, 0,)-time () > 0) &&
SUBSTR ($result, ten, +) = = substr (MD5 (substr ($result,) $keyb), 0, 16)) {
Return substr ($result, 26);
} else {
Return ';
}
} else {
The dynamic key is stored in the ciphertext, which is why the same clear text, the production of different ciphertext can be decrypted after the reason
Because the encrypted ciphertext may be some special characters, the copying process may be lost, so the base64 encoding
Return $KEYC. Str_replace (' = ', ' ', Base64_encode ($result));
}
}

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

Usage:
Copy the Code code 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, add decryption function encrypt ():
Copy CodeThe 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));
}
}

function Encrypt ($string, $operation, $key) $string: A string that requires encryption and decryption, $operation: Determines whether it is encrypted or decrypted, e means encryption, and d means decryption; $key: Key.
Usage:
Copy the Code code as follows:
$STR = ' abc ';
$key = ' www.helloweba.com ';
$token = Encrypt ($str, ' E ', $key);
echo ' encryption: '. Encrypt ($str, ' E ', $key);
Echo ' decryption: '. Encrypt ($str, ' D ', $key);

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