Are transaction signatures unique?

StarscreamAug 12, 2023

Is it possible to have 2 transactions with the same signature when using the same private key?

scholtzLudo, Everyday AlgonautAug 12, 2023

On Algorand the hash of the transaction is transaction id. So if you attempt to create same transactions it will be one transaction and second time you try to add it to the blockchain it will tell you that it is already there.

If you want them to be unique, add there nonce, make the transaction note field different or change for example valid until time.

When you sign the transaction you always sign all data, so technically it is not possible to create two transactions with same valid signature.

StarscreamAug 13, 2023

How do I obtain TxID of a transaction on the blockchain? I am using algod API, but do not see “txid” anywhere when I query a block. I’m not interested in using indexer.

scholtzLudo, Everyday AlgonautAug 13, 2023

I use for example this method to calculate txId from core algod data

github.com

scholtz/vote-coin-indexer/blob/master/src/algo/computeTransactionId.ts

import algosdk from "algosdk";

const computeTransactionId = (gh: Buffer, gen: string, stib: any)=> {
	const t = stib.txn as algosdk.EncodedTransaction;

	// Manually add gh/gen to construct a correct transaction object
	t.gh = gh;
	t.gen = gen;

	const stxn = {
		txn: algosdk.Transaction.from_obj_for_encoding(t),
	} as algosdk.SignedTransaction;

	if ("sig" in stib) {
		stxn.sig = stib.sig;
	}

	if ("lsig" in stib) {
		stxn.lsig = stib.lsig;
	}

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StarscreamAug 13, 2023

Is there a way to do this without using the SDK? I mean, using any programming language, is there a generic formula to calculate the TxID from the JSON information on a block provided by the algod API?

scholtzLudo, Everyday AlgonautAug 13, 2023

all sdks are open source so technically you can calculate it on your own… the txid is just the hash of something so it should not be difficult

StarscreamAug 14, 2023

Would you happen to know exactly what the formula is? I can’t seem to find it anywhere.

scholtzLudo, Everyday AlgonautAug 14, 2023

github.com

algorand/js-algorand-sdk/blob/28489e19a0488549253ea9dd9291db76a8c8bbda/src/transaction.ts#L1165C1-L1175C4


      
          
          rawTxID() {
            const enMsg = this.toByte();
            const gh = Buffer.from(utils.concatArrays(this.tag, enMsg));
            return Buffer.from(nacl.genericHash(gh));
          }
          
          txID() {
            const hash = this.rawTxID();
            return base32.encode(hash).slice(0, ALGORAND_TRANSACTION_LENGTH);
          }

github.com

FrankSzendzielarz/dotnet-algorand-sdk/blob/f12410bd1f1c7646fe4c1768f55c54c1113af000/dotnet-algorand-sdk/Algod/Model/Transactions/Transaction.cs#L198


      
              return new Digest(Digester.Digest(BytesToSign()));
          }
          
              
          /// <summary>
          /// Return transaction ID as string
          /// </summary>
          /// <returns></returns>
          public string TxID()
          {
              return Base32.EncodeToString(this.RawTxID().Bytes, false);
          }
          
          public void SetFee(ulong fee)
          {
              if (fee < MIN_TX_FEE_UALGOS) fee = MIN_TX_FEE_UALGOS;
              Fee = fee;
          }
          
          public SignedTransaction Sign(Account signingAccount)
          {

I still dont know what language you are coding in…

StarscreamAug 15, 2023

Thanks. But how am I suppose to get the TxID from the algod JSON response that looks like this:

{
  "block": {
    "earn": 27521,
    "fees": "A7NMWS3NT3IUDMLVO26ULGXGIIOUQ3ND2TXSER6EBGRZNOBOUIQXHIBGDE",
    "frac": 2061697303,
    "gen": "testnet-v1.0",
    "gh": "SGO1GKSzyE7IEPItTxCByw9x8FmnrCDexi9/cOUJOiI=",
    "prev": "blk-5VT353VFJZQU4CAW3JK5JKZLCJ4MJFANEA7C76LRAJV77BK2TD3A",
    "proto": "https://github.com/algorandfoundation/specs/tree/abd3d4823c6f77349fc04c3af7b1e99fe4df699f",
    "rnd": 32161726,
    "rwcalr": 32500000,
    "rwd": "7777777777777777777777777777777777777777777777777774MSJUVU",
    "seed": "gKpQ4G4LdhREw5bw86wCU+sG5oFEISMjGNGLQ3wy7Fc=",
    "spt": {
      "0": {
        "n": 32161792
      }
    },
    "tc": 275213679,
    "ts": 1692057423,
    "txn": "RMrqMRugJyEFVsZQb8pUCoUWKwXwDbSo5+zA6ol/xU4=",
    "txn256": "KWxIx/ANMp8SY83Cv3OhYd3jha8OLYt3HV/12LSjo5Y=",
    "txns": [
     ...,
      {
        "hgi": true,
        "sig": "fKpBB24QFNl4trtdhNNjmqmbpWear8MxtbbPyLWzngm6Ki4k1pgAVVdEC2R75kqdDGtiDAo3cmcfu6dX6No9Bg==",
        "txn": {
          "fee": 1000,
          "fv": 32161724,
          "lv": 32162724,
          "note": "eyJ0eF90eXBlIjogImNoZWNrX2luIiwgInR5cGUiOiAibSIsICJsb2NhdGlvbiI6IHsibG9jYXRpb25fbmFtZSI6ICIzMDMwIiwgImxvbmdpdHVkZSI6IDMwLCAibGF0aXR1ZGUiOiAzMH0sICJpc19hc2xlZXAiOiBmYWxzZSwgIm5vdGljZV9vZl9tZWV0aW5nIjogW119",
          "rcv": "6WMABAAUQSBYXEN7ARZX7FYO3N65IVMR6HCF7GPWM36YR6XXITEMRBMHQY",
          "snd": "3ELSBOZDRV2BSCI4W3QSRFC4KXD3K6YSJ722GRKHOSLCCOJYBWPS4PKRH4",
          "type": "pay"
        }
      }
    ]
  }
}

By the way, I am using the Ruby language.

scholtzLudo, Everyday AlgonautAug 15, 2023

Sorry, i cannot help you with ruby… i know typescript and this is how it is done there:

github.com

scholtz/vote-coin-indexer/blob/4bb4c9c83021bd29152a44b9168c9ca561093bd3/src/app.ts#L53C0-L59C0


      
          for (const stxn of block.block.txns) {
            countProcessedTxns++;
            try {
              if (!stxn.txn.note) continue;
              const note = Buffer.from(stxn.txn.note).toString('utf-8');
              if (!note.startsWith('avote-')) continue;
              const txId = computeTransactionId(block.block.gh, block.block.gen, stxn);

Perhaps someone from algoand can help? The best would be to write on algorand discord to dev channel…

StarscreamAug 20, 2023

Ok, but do you know if TxID is always 52 characters long?

scholtzLudo, Everyday AlgonautAug 20, 2023

i think it is true right now, but in 10 years period many things can change…