Function seal 

pub fn seal<T: Serialize>(
    obj: &T,
    key: &SealingKey,
    aad: impl AsRef<[u8]>,
) -> Result<Vec<u8>>

Encodes and encrypts the given obj with additional associated data (or b"" if None). Use unseal to revert.

Uses a non self-describing encoding format for T, so seal is not suitable for long-lived data that might change.