IdentifierMasking.cs

public class IdentifierMasking
{
    private static byte[] _key;

    public IdentifierMasking(byte[] key = null)
    {
        _key = key ?? Sodium.SecretBox.GenerateKey();
    }

    public string RevealIdentifier(string hidden)
    {
        Span<byte> data = SimpleBase.Base58.Bitcoin.Decode(hidden);
        byte[] nonce = data.Slice(0, 12).ToArray();
        byte[] encrypted = data.Slice(12).ToArray();
        byte[] plain = Sodium.SecretAeadAes.Decrypt(encrypted, nonce, _key);
        return Encoding.UTF8.GetString(plain);

    }
    public string HideIdentifier(string id)
    {
        byte[] nonce = Sodium.SecretAeadAes.GenerateNonce();
        byte[] encrypted = Sodium.SecretAeadAes.Encrypt(Encoding.UTF8.GetBytes(id), nonce, _key);

        return SimpleBase.Base58.Bitcoin.Encode(nonce.Concat(encrypted).ToArray());
    }
}