pub fn open(
c: &[u8],
n: &Nonce,
pk: &PublicKey,
sk: &SecretKey,
) -> Result<Vec<u8>, ()>Expand description
open() verifies and decrypts a ciphertext c using the receiver’s secret key sk,
the senders public key pk, and a nonce n. It returns a plaintext Ok(m).
If the ciphertext fails verification, open() returns Err(()).