open method
Implementation
@override
Uint8List open(Uint8List nonceAndCiphertext, Uint8List key) {
var nonce = nonceAndCiphertext.sublist(
0, sodium.crypto_secretbox_NONCEBYTES as int);
var ciphertext =
nonceAndCiphertext.sublist(sodium.crypto_secretbox_NONCEBYTES as int);
return sodium.crypto_secretbox_open_easy(ciphertext, nonce, key);
}