Seal (encrypt) data

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- PHP Manual
- OpenSSL Functions
- Seal (encrypt) data

# openssl_seal

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

openssl_seal — Seal (encrypt) data

### Description

openssl_seal(
#[\SensitiveParameter] string `$data`,
string `&$sealed_data`,
array `&$encrypted_keys`,
array `$public_key`,
string `$cipher_algo`,
string `&$iv` = `null`
): int|false

openssl_seal() seals (encrypts) `data` using the specified `cipher_algo` with a randomly generated secret key. The key is then encrypted with each of the public keys in `public_key` array, and each encrypted envelope key is returned in `encrypted_keys`. This allows sealed data to be sent to multiple recipients (provided their public keys are available). Each recipient must receive both the sealed data and the envelope key that was encrypted with the recipient's public key. The IV (Initialization Vector) is generated, and its value is returned in `iv`.

### 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 for PHP versions prior to 8.0 is (`'RC4'`) which is considered insecure. It is strongly recommended to explicitly specify a secure cipher method.

`iv`

  The initialization vector for decryption of `data`. It is required if the cipher method requires IV. This can be found out by calling openssl_cipher_iv_length() with `cipher_algo`.

  Caution

  The IV cannot be set explicitly. Any value set in it is overwritten by randomly generated value.

### 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
    $data = "test";

    // fetch public keys
    $pk1 = openssl_get_publickey("file://cert1.pem");
    $pk2 = openssl_get_publickey("file://cert2.pem");

    // seal message, only owners of $pk1 and $pk2 can decrypt $sealed with keys
    // $ekeys[0] and $ekeys[1] respectively.
    if (openssl_seal($data, $sealed, $ekeys, array($pk1, $pk2), 'AES256', $iv) > 0) {
        // possibly store the $sealed and $iv values and use later in openssl_open
        echo "success\n";
    }
    ?>

### See Also

- openssl_open() - Open sealed data