(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)
openssl_seal — Seal (encrypt) data
Description
openssl_seal(
string $data,
string &$sealed_data,
array
&$encrypted_keys,
array $public_key,
string $cipher_algo,
string &$iv = null
): int|false
Parameters
data The data to seal.
sealed_data The sealed data.
encrypted_keys Array of encrypted keys.
public_key Array of OpenSSLAsymmetricKey instances containing public keys.
cipher_algo The cipher method.
Caution
The default value ('RC4') is considered insecure. It is strongly recommended to explicitly specify
a secure cipher method.
iv The initialization vector.
Return Values
Returns the length of the sealed data on success, or false on error. If successful the sealed data is returned in sealed_data, and the envelope keys in encrypted_keys.
Changelog
| Version | Description |
|---|
| 8.0.0
| public_key accepts an array of OpenSSLAsymmetricKey instances now; previously, an array of resources of type OpenSSL key was accepted.
|
| 8.0.0
| cipher_algo is no longer an optional parameter.
|
| 8.0.0
| iv is nullable now.
|
Examples
Example #1 openssl_seal() example
<?php
// $data is assumed to contain the data to be sealed
// fetch public keys for our recipients, and ready them
$fp = fopen("/src/openssl-0.9.6/demos/maurice/cert.pem", "r");
$cert = fread($fp, 8192);
fclose($fp);
$pk1 = openssl_get_publickey($cert);
// Repeat for second recipient
$fp = fopen("/src/openssl-0.9.6/demos/sign/cert.pem", "r");
$cert = fread($fp, 8192);
fclose($fp);
$pk2 = openssl_get_publickey($cert);// seal message, only owners of $pk1 and $pk2 can decrypt $sealed with keys
// $ekeys[0] and $ekeys[1] respectively.
openssl_seal($data, $sealed, $ekeys, array($pk1, $pk2));// free the keys from memory
openssl_free_key($pk1);
openssl_free_key($pk2);
?>
amer.alhabsi AT gmail DOT
com ¶
6 years ago
while the default is using RC4, it is possible to use other more secure algorithms. These are specified as the fifth parameter. Also, one needs to add an initialization vector (random bytes). Eg.
<?php
$data = "This is top secret.";
// fetch public keys for our recipients, and ready them
$cert = file_get_contents('./cert.pem');$pk1 = openssl_get_publickey($cert);
$iv = openssl_random_pseudo_bytes(32);
openssl_seal($data, $sealed, $ekeys, array($pk1), "AES256", $iv);// free the keys from memory
openssl_free_key($pk1);
echo base64_encode($sealed);
?>
Dominik M. ¶
1 year ago
Please note that openssl_seal() cannot be used for EC encryption.
Took me literally two hours to find out because the OpenSSL documentation is so bad.
devel@no-spam ¶
17 years ago
"seals (encrypts) data by using RC4 with a randomly generated secret key"
It should be noted that the randomly generated secret key is 128 bits long (openssl: EVP_rc4(void): RC4 stream cipher. This is a variable key length cipher with default key length 128 bits.)
bowfingermail at gmx dot net ¶
6 years ago
According to several sources (e.g. crypto101.io or Wikipedia) RC4 is not safe and not supposed to be used anymore.
So, shouldn't openssl_seal use another stream cipher in place of RC4?
aaron dot lawrence at umajin dot
com ¶
1 year ago
Some critical details that are not in the docs, nor widely written about elsewhere.
- The envelope key is a 128-bit RSA key, randomly generated.
- The data is encrypted with (A)RC4 using the envelope key.
- The envelope key is encrypted for transmission with PKCS1 v1.5. It is NOT the OAEP padding variant. PKCS1 v1.5 is even older, and not widely supported anymore.
At least this was true for openssl_seal in PHP 7.2 that we are using.
(Note: In Python you can decrypt this envelope key with the Cryptography package, using padding.PKCS1v15())
The combination of RC4 and PKCS1 v1.5 make this function actually semi-obsolete for security use in my opinion.
hfuecks at nospam dot org ¶
14 years ago
openssl_seal() can work well when you need to pass data securely to other platforms / languages. What openssl_seal() does is;
1. Generate a random key
2. Encrypt the data symmetrically with RC4 using the random key
3. Encrypt the random key itself with RSA using the public key / certificate
4. Returns the encrypted data and the encrypted key
So to decrypt the steps are simply;
1. Decrypt the key using RSA and your private key
2. Decrypt the data using RC4 and the decrypted key
The trickiest part may be figuring out how handle the private key - BouncyCastle ( http://www.bouncycastle.org/ ) provides a PEMReader for Java and C# while Not Yet commons-ssl ( http://juliusdavies.ca/commons-ssl/ ) has a KeyStoreBuilder to build Java keystores out of a PEM certificate.
A complete example in Java is described at http://blog.local.ch/archive/2007/10/29/openssl-php-to-java.html
