openssl_decrypt

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

openssl_decrypt — Decrypts data

Descrizione

openssl_decrypt(
    string $data,
    string $cipher_algo,
    string $passphrase,
    int $options = 0,
    string $iv = "",
    ?string $tag = null,
    string $aad = ""
): string|false

Takes a raw or base64 encoded string and decrypts it using a given method and key.

Elenco dei parametri

data: The encrypted message to be decrypted.
cipher_algo: The cipher method. For a list of available cipher methods, use openssl_get_cipher_methods().
passphrase: The key.
options: options can be one of OPENSSL_RAW_DATA, OPENSSL_ZERO_PADDING.
iv: A non-NULL Initialization Vector.
tag: The authentication tag in AEAD cipher mode. If it is incorrect, the authentication fails and the function returns false.

Attenzione
The length of the tag is not checked by the function. It is the caller's responsibility to ensure that the length of the tag matches the length of the tag retrieved when openssl_encrypt() has been called. Otherwise the decryption may succeed if the given tag only matches the start of the proper tag.
aad: Additional authenticated data.

Valori restituiti

The decrypted string on success o false in caso di fallimento.

Errori/Eccezioni

Emits an E_WARNING level error if an unknown cipher algorithm is passed via the cipher_algo parameter.

Emits an E_WARNING level error if an empty value is passed in via the iv parameter.

Log delle modifiche

Versione	Descrizione
8.1.0	`tag` is now nullable.
7.1.0	The `tag` and `aad` parameters were added.

Vedere anche:

openssl_encrypt() - Encrypts data

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User Contributed Notes 4 notes

down

Hernanibus ¶

8 years ago


Parameters may seem obvius to some but not for everyone so:



- $data can be as the description says raw or base64. If no $option is set (this is, if value of 0 is passed in this parameter), data will be assumed to be base64 encoded. If parameter OPENSSL_RAW_DATA is set, it will be understood as row data.



- $password (key) is a String of [pseudo] bytes as those generated by the function openssl_random_pseudo_bytes().



- $options as (as for 2016) two possible values OPENSSL_RAW_DATA and OPENSSL_ZERO_PADDING. Setting both can be done by OPENSSL_RAW_DATA|OPENSSL_ZERO_PADDING. If no OPENSSL_ZERO_PADDING is specify, default pading of PKCS#7 will be done as it's been observe by [openssl at mailismagic dot com]'s coment in openssl_encrypt()



- $iv is as in the case of $password, a String of bytes. Its length depends on the algorithm used. May be the best way to generate an $iv is by:



<?php

    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('your algorithm'));// for example you algorithm = 'AES-256-CTR'

?>

down

ittasks at gmail dot com ¶

11 years ago


in case that hosting do not provide openssl_encrypt decrypt functions - it could be mimiced via commad prompt executions  
this functions will check is if openssl is installed and try to use it by default

function sslPrm()
{
 return array("your_password","IV (optional)","aes-128-cbc");
}
function sslEnc($msg)
{
  list ($pass, $iv, $method)=sslPrm();
  if(function_exists('openssl_encrypt'))
     return urlencode(openssl_encrypt(urlencode($msg), $method, $pass, false, $iv));
  else
     return urlencode(exec("echo \"".urlencode($msg)."\" | openssl enc -".urlencode($method)." -base64 -nosalt -K ".bin2hex($pass)." -iv ".bin2hex($iv)));
}
function sslDec($msg)
{
  list ($pass, $iv, $method)=sslPrm();
  if(function_exists('openssl_decrypt'))
     return trim(urldecode(openssl_decrypt(urldecode($msg), $method, $pass, false, $iv)));
  else
     return trim(urldecode(exec("echo \"".urldecode($msg)."\" | openssl enc -".$method." -d -base64 -nosalt -K ".bin2hex($pass)." -iv ".bin2hex($iv))));
}

//example of usage:
$r= sslEnc("This is encryption/decryption test!");
echo "<br>\n".$r.":".sslDec($r);

down

lucianonapoli at yahoo dot it ¶

7 years ago


The parameter string $password must be in binary form and is derived from the exadecimal key value.

Example:

encrypting in command line console with openssl
openssl AES-256-CBC -K 5ae1b8a17bad4da4fdac796f64c16ecd -iv 34857d973953e44afb49ea9d61104d8c -in doc.txt -out doc.enc.txt

decripting in php
$key = hex2bin('5ae1b8a17bad4da4fdac796f64c16ecd');
$iv = hex2bin('34857d973953e44afb49ea9d61104d8c');

$output = openssl_decrypt($encstr, 'AES-256-CBC', $key, OPENSSL_RAW_DATA, $iv);

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markagius dot co dot uk ¶

7 years ago


openssl_decrypt(..) works with most but not all method types.
This list can vary, depending on the data (Message) and key (Password) used.

See the following code and edit the $text and $password values.
Code checks if text is the same after encrypting then decrypting it.

Note:
  You can still use openssl_encrypt(..) with;
  User enters 'Log-in password'
  (Encrypted and stored using openssl_encrypt)
  Next time.
  User logs-in with 'Log-in password'
  (Check that encrypted 'Log-in password' = stored data)

<CODE>
  // Please edit $password=... and $text=...

  $password = "This is a journey into sound";

  $text = "";
  for($charNo=0; $charNo<=255; $charNo=$charNo+1){
    // if($charNo==127) {$charNo=$charNo+1;}
    if(!$charNo<127){
      // $text = $text."&#x".strtoupper(dechex($charNo)).";";
      $text = $text.chr($charNo);
    } else {
      $text = $text.chr($charNo);
    }
  }

$text = "This is a test message.";

  print "<TABLE BORDER=\"1\">\n";
  print "<TR><TD><B>Encryption type:</B></TD><TD><B>String after converting back:</B></TD></TR>\n";
  $ciphers = openssl_get_cipher_methods();
  for($pointer=0; $pointer<count($ciphers); $pointer=$pointer+1){
    $edit  = EncryptDecrypt($text, true,  $password, $ciphers[$pointer]);
    $check = EncryptDecrypt($edit, false, $password, $ciphers[$pointer]);
    if($text!=$check){
      $info  = $check;
      print "<TR><TD>".$ciphers[$pointer]."</TD><TD>".$info."</TD></TR>\n";
    }
  }
  print "</TABLE>\n";

function EncryptDecrypt($oldText, $encryptIt=true, $password="PASSWORD", $encryptType=""){
  $ciphers = openssl_get_cipher_methods();
  $foundEncType = false;
  for($pointer=0; $pointer<count($ciphers); $pointer=$pointer+1){
    if($ciphers[$pointer]==$encryptType){$foundEncType=true;}
  }
  if(!$foundEncType){
    $encryptType = "RC2-64-CBC"; // Default value used if not set or listed.
  }
  if($encryptIt){
    $newText = openssl_encrypt($oldText,$encryptType,$password);
  } else {
    $newText = openssl_decrypt($oldText,$encryptType,$password);
  }
  return $newText;
}
</CODE>
The following (sometimes) don't work:
    DES-EDE3-CFB1    (sometimes)
    aes-128-gcm
    aes-192-gcm
    aes-256-gcm
    des-ede3-cfb1        (sometimes)
    id-aes128-GCM
    id-aes192-GCM
    id-aes256-GCM

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