Implementation
TransactionBuilder build(seed, int index,
{String curve = "ed25519", String hashAlgo = "sha256"}) {
KeyPair keypair = crypto.deriveKeyPair(seed, index, curve: curve);
KeyPair nextKeypair = crypto.deriveKeyPair(seed, index + 1, curve: curve);
Uint8List address = crypto.hash(nextKeypair.publicKey, algo: hashAlgo);
this.address = address;
this.previousPublicKey = keypair.publicKey;
this.timestamp = new DateTime.now().millisecondsSinceEpoch;
this.previousSignature =
crypto.sign(this.previousSignaturePayload(), keypair.privateKey);
return this;
}