string secretKey = "YJExjGFZvdbSKTeVgLUQFupOzFWfSlRm"; // The secret key must have 32 chars.
byte[] hashSeed  =  Encoding.ASCII.GetBytes(secretKey); // Convert it into byte array

byte[] privateKey = new byte[64];
byte[] publicKey =  new byte[32];

Ed25519.KeyPairFromSeed(out publicKey, out privateKey, hashSeed);

//...
byte[] privateKey = Ed25519.ExpandedPrivateKeyFromSeed(hashSeed);

//...
byte[] publicKey = Ed25519.PublicKeyFromSeed(hashSeed);

var token = new PasetoBuilder<Version2>()
		.WithKey(privateKey)
		.AddClaim("example", "Hello Paseto!")
		.Expiration(DateTime.UtcNow.AddHours(24))
		.AsPublic() // Purpose
		.Build();

var encoder = new PasetoEncoder(cfg => cfg.Use<Version2>(privateKey)); // default is public purpose
var token = encoder.Encode(new PasetoPayload
{
	{ "example", "Hello Paseto!" },
	{ "exp", DateTime.UtcNow.AddHours(24) }
});

var payload = new PasetoBuilder<Version2>()
		.WithKey(publicKey)
		.AsPublic() // Purpose
		.Decode(token);

var decoder = new PasetoDecoder(cfg => cfg.Use<Version2>(publicKey)); // default is public purpose
var payload = decoder.Decode(token);