Anonymous public-key encryption

# sodium_crypto_box_seal

(PHP 7 >= 7.2.0, PHP 8)

sodium_crypto_box_seal — Anonymous public-key encryption

### Description

sodium_crypto_box_seal(#[\SensitiveParameter] string `$message`, string `$public_key`): string

Encrypt a message such that only the recipient can decrypt it.

Unlike with sodium_crypto_box(), you only need to know the recipient's public key to use sodium_crypto_box_seal(). One consequence of this convenience, however, is that the ciphertext isn't bound to a static public key, and is therefore not authenticated. Hence, anonymous public-key encryption.

sodium_crypto_box_seal() still provides ciphertext integrity. Just not sender identity authentication.

If you also need sender authentication, the sodium_crypto_sign() functions are likely the best place to start.

### Parameters

`message`
  The message to encrypt.
`public_key`
  The public key that corresponds to the only key that can decrypt the message.

### Return Values

A ciphertext string in the format of (one-time public key, encrypted message, authentication tag).

### Examples

Example #1 sodium_crypto_box_seal() example

`<?php
$keypair = sodium_crypto_box_keypair();
$public_key = sodium_crypto_box_publickey($keypair);
// Obfuscated plaintext to make the example more fun
$plaintext_b64 = "V3JpdGluZyBzb2Z0d2FyZSBpbiBQSFAgY2FuIGJlIGEgZGVsaWdodCE=";
$decoded_plaintext = sodium_base642bin($plaintext_b64, SODIUM_BASE64_VARIANT_ORIGINAL);
$sealed = sodium_crypto_box_seal($decoded_plaintext, $public_key);
var_dump(base64_encode($sealed));
$opened = sodium_crypto_box_seal_open($sealed, $keypair);
var_dump($opened);
?>`

The above example will output something similar to:

    string(120) "oRBXXAV4iQBrxlV4A21Bord8Yo/D8ZlrIIGNyaRCcGBfpz0map52I3xq6l+CST+1NSgQkbV+HiYyFjXWiWiaCGupGf+zl4bgWj/A9Adtem7Jt3h3emrMsLw="
    string(41) "Writing software in PHP can be a delight!"

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