sodium_crypto_secretbox

Authenticated shared-key encryption

&reftitle.description; `string` `sodium_crypto_secretbox` `string` `message` `string` `nonce` `string` `key`

Encrypt a message with a symmetric (shared) key.

&reftitle.parameters;

`message`

- The plaintext message to encrypt.

`nonce`

- A number that must be only used once, per message. 24 bytes long. This is a large enough bound to generate randomly (i.e. `random_bytes`).

`key`

- Encryption key (256-bit).

&reftitle.returnvalues;

Returns the encrypted string.

&reftitle.errors;

- If `nonce` has a length of bytes different than `SODIUM_CRYPTO_SECRETBOX_NONCEBYTES` (24 bytes), a `SodiumException` will be thrown.

- If `key` has a length of bytes different than `SODIUM_CRYPTO_SECRETBOX_KEYBYTES` (32 bytes), a `SodiumException` will be thrown.

- Throws a `SodiumException` on failure.

&reftitle.examples;

### `sodium_crypto_secretbox` example

    <?php
    // The $key must be kept confidential
    $key = sodium_crypto_secretbox_keygen();
    // Do not reuse $nonce with the same key
    $nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
    $plaintext = "message to be encrypted";
    $ciphertext = sodium_crypto_secretbox($plaintext, $nonce, $key);

    var_dump(bin2hex($ciphertext));
    // The same nonce and key are required to decrypt the $ciphertext
    var_dump(sodium_crypto_secretbox_open($ciphertext, $nonce, $key));
    ?>

&example.outputs.similar;

    string(78) "3a1fa3e9f7b72ef8be51d40abf8e296c6899c185d07b18b4c93e7f26aa776d24c50852cd6b1076"
    string(23) "message to be encrypted"

&reftitle.seealso;

- `sodium_crypto_secretbox_open`
- `sodium_crypto_secretbox_keygen`
- `random_bytes`