Calculating Transaction ID

AlgoSDK
1

Given that the transaction ID is not contained in the blockchain it has to be calculated after reading them out of the block. What am I doing wrong here:

    BlockResponse resp = blockResp.body();
    if (resp.block.containsKey("txns")) {
        var list = (List<Map<String, Object>>)resp.block.get("txns");
        for (var entry : list) {
            String s = jsonMapper.writeValueAsString(entry);
            SignedTransaction trans = jsonMapper.readValue(s, SignedTransaction.class);
            String id = trans.tx.txID();
            }
        }
    }

It seems that the id doesn’t match with the ones in the app.

Any ideas what I’m doing wrong?

Also are tx IDs unique or just unique for a specific block?

2

The process is more complex as the transactions in blocks are compressed to remove some fields such as the genesis ID and genesis Hash (and only keep a flag indicating if those fields were present).

See for example indexer/importer.go at 26d521746522237b1554c06dc370b6fe0bbe2f24 · algorand/indexer · GitHub

The simplest solution is to fetch the block from the indexer, as opposed to algod: indexer - Algorand Developer Portal
The indexer returns blocks with all the information you may be interested in (transaction IDs, close amounts, …)

3

I may be mistaken, but doesn’t the indexer require an archival node? I’d like to avoid that.

I’m not seeing the flag in the json, so I can assume that algod doesn’t provide me with that information?

4

The indexer requires a full node.
I see the flag as hgi:

$ curl -s "https://testnet.algoexplorerapi.io/v2/blocks/13819291" | jq
{
  "block": {
    "earn": 27162,
    "fees": "A7NMWS3NT3IUDMLVO26ULGXGIIOUQ3ND2TXSER6EBGRZNOBOUIQXHIBGDE",
    "frac": 9733995065,
    "gen": "testnet-v1.0",
    "gh": "SGO1GKSzyE7IEPItTxCByw9x8FmnrCDexi9/cOUJOiI=",
    "prev": "blk-PLQJFVKQY5YKDU5P66ADL52WIGM44GOGBO6XYBFEWHAAMRFBMFYA",
    "proto": "https://github.com/algorandfoundation/specs/tree/ac2255d586c4474d4ebcf3809acccb59b7ef34ff",
    "rate": 19999960,
    "rnd": 13819291,
    "rwcalr": 14000000,
    "rwd": "7777777777777777777777777777777777777777777777777774MSJUVU",
    "seed": "FuzMUjU9svsxVMkzeb+xjKowKaabEuVYmcWl6f+ypk4=",
    "tc": 15649796,
    "ts": 1619616946,
    "txn": "z3MximXiJdPy2yVbTDt965vCUT2Zgfqr/clB1ZRy/Do=",
    "txns": [
      {
        "hgi": true,
        "sig": "zyh2aINzuHkR88G1bIrKZldti2X+/5i4ZYWQuAn5XiDWhlZYk1Gna+SDII+LVA4/wd2TisrwwU1q9sWDOk7qDw==",
        "txn": {
          "arcv": "UWGOC45RXKERIWFF2Z6LR4VHSEDDHLRH7YLZQGS7WCZN5OSNZZLEDGWZ7A",
          "fee": 1000,
          "fv": 13819289,
          "lv": 13820289,
          "note": "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",
          "snd": "SHTUSO6YCTH5NV74MU2HC4VOKFGX3NLOUVD5TCZCXQWDSX6JCE4SMZMOYA",
          "type": "axfer",
          "xaid": 408947
        }
      }
    ]
  }
}
5

Ah, they didn’t map that flag for the java objects, makes sense. Turns out the transaction I was looking at didn’t have that flag, so no genesis hash or id required.

Guess I have to take a look at how the index does it. I’m almost certain all fields are correctly set the moment it calculates the txid. Maybe I’m missing something.

6

So I did some testing, message sent from the provided SDK, have the exact same transaction ID once I read them back from the block (including gensisID and hash).

But when I want to check the ID of a transaction sent by the official wallet app (no HGI entry) the txId doesn’t match up.

7

Does the indexer get it right?
Can you link to a transaction on TestNet?

8

Z5RDNFGJF54FDJBIJ6FNCCENPBTCYG4XJOLORJ4D43BKUCGG2SVQ

https://testnet.algoexplorer.io/tx/Z5RDNFGJF54FDJBIJ6FNCCENPBTCYG4XJOLORJ4D43BKUCGG2SVQ

I don’t have a node with an indexer.

9

hgi is indeed just for the genesis name.
On MainNet and TestNet, genesis hash is always mandatory and always must be added.

Does this work when you add it?

1 Like
10

That’s it!

Didn’t know the hash was required (although it makes sense)