# sodium_crypto_aead_chacha20poly1305_ietf_decrypt

(PHP 7 >= 7.2.0, PHP 8)

sodium_crypto_aead_chacha20poly1305_ietf_decrypt — Verify that the ciphertext includes a valid tag

### Descripción

sodium_crypto_aead_chacha20poly1305_ietf_decrypt(
string `$ciphertext`,
string `$additional_data`,
string `$nonce`,
string `$key`
): string|false

Verify then decrypt with ChaCha20-Poly1305 (IETF variant).

The IETF variant uses 96-bit nonces and 32-bit internal counters, instead of 64-bit for both.

### Parámetros

`ciphertext`

  Must be in the format provided by sodium_crypto_aead_chacha20poly1305_ietf_encrypt() (ciphertext and tag, concatenated).

`additional_data`

  Additional, authenticated data. This is used in the verification of the authentication tag appended to the ciphertext, but it is not encrypted or stored in the ciphertext.

`nonce`

  A number that must be only used once, per message. 12 bytes long.

`key`

  Encryption key (256-bit).

### Valores devueltos

Returns the plaintext on success, o `false` en caso de error.