Algorand sign transaction

signTxn.js

 signTxn(sk: Uint8Array) {
    // construct signed message
    const sTxn: EncodedSignedTransaction = {
      sig: this.rawSignTxn(sk),
      txn: this.get_obj_for_encoding(),
    };
    // add AuthAddr if signing with a different key than From indicates
    const keypair = nacl.keyPairFromSecretKey(sk);
    const pubKeyFromSk = keypair.publicKey;
    if (
      address.encodeAddress(pubKeyFromSk) !==
      address.encodeAddress(this.from.publicKey)
    ) {
      sTxn.sgnr = Buffer.from(pubKeyFromSk);
    }
    return new Uint8Array(encoding.encode(sTxn));
  }