7
votes
Accepted
How to calculate txid for segwit transactions?
The txid of a segwit transaction is computed by first dropping all the witnesses, and encoding it in legacy notation, and then computing the double-SHA256 hash of it.
This is the only possible way, ...
- 102k
6
votes
SegWit and previous hash: txid or wtxid, or either?
Inside transaction inputs, you have to refer to previous transactions using the txid. Allowing a wtxid there would be (1) a hard fork and (2) defeating the purpose, as it'd make transactions malleable ...
- 102k
6
votes
Accepted
Duplicate transactions in blockchain
Transactions can have multiple outputs. What you show are two outputs created by the same transaction.
The output positions are enumerated with the vout field. As the first one is vout = 0, the two ...
- 73k
6
votes
Is txid a required field on all transactions?
Txid can’t be missing since it’s just a hash of the transaction data
- 3,529
6
votes
Accepted
When calculating the hash of transaction, why is the version used as "01000000" instead of "00000001"?
Because it's encoded as a little endian number, meaning the least significant byte goes first.
Example:
Number 1234 would be encoded as byte sequence 000004D2 when encoded as 4-byte big endian, and it ...
- 1,014
4
votes
Accepted
What is the impact of purposely sending a signed message with zero fee?
The underlying motivation behind transaction fees is to compensate for resource utilisation as there is always an inherent cost when validating transactions (Electricity - CPU usage) and relaying ...
- 2,418
4
votes
How are transaction IDs generated and how are they then changed by transaction malleability?
The transaction ID is the SHA256d(signedTransaction) = SHA256(SHA256(signedTransaction)). Sha256d is SHA256 applied two times.
Example:
Let us consider the transaction with ID ...
- 1,047
4
votes
How to compute SegWit txid?
Is data that hashed as txid includes witness?
No, the txid is the hash of just [nVersion][txins][txouts][nLockTime] which is the same as a serialized non-witness transaction. That means the signature ...
- 11.8k
4
votes
Values for txid and vout for create a coinbase transaction
The coinbase transaction contains a single input, which has txid set to 0000000000000000000000000000000000000000000000000000000000000000 and vout set to 0xFFFFFFFF.
- 11.8k
4
votes
Accepted
Developing a Bitcoin POS (Payment Page) - How do I identify the transaction
The only right way of of doing this is generating a new address for every expected payment, and then waiting until you've received that amount on that address.
- 102k
4
votes
Accepted
How does a node get information from the TxID?
Yes, all txids are calculated only from non-witness data. While many nodes have a complete copy of the blockchain (which does contain all transactions), most nodes do not have a full transaction index....
- 73k
4
votes
How are TXIDs determined from the raw hex data of a block? Also, what is the coinbase transaction?
It is a little-endian double SHA256 hash of the binary transaction data
Some subtle mistakes I've seen people make:
Not converting hex to binary before hashing. Hash("DEADBEEF") is not the ...
- 25.3k
3
votes
Accepted
Ripple: How to calculate transaction ID (TXID)
The transaction ID is calculated by prepending the bytes 0x54, 0x58, 0x4e, 0x00 to the signed transaction and then taking the SHA512Half of this input.
Example for a signed transaction, bytes are ...
- 1,047
3
votes
Accepted
Why didn't Bitcoin implement segwit in the first place?
Why didn't Bitcoin implement segwit in the first place?
The reason Bitcoin didn't initially have SegWit is up to interpretation, I would say that it simply was not thought of prior to transaction ...
- 1,013
3
votes
Find message attached to Bitcoin transaction?
Transactions do not have comments attached to them. Any comments are local to a person's wallet only. They are not broadcast to the network nor are they actually attached to a transaction. So you ...
- 68.6k
3
votes
Accepted
Create raw transaction what txid
In the console do listunspent
that will show you all the UTXO in your wallet including the txids.
You can type help to get a list of commands,
then help <command> to get details about each ...
- 1,630
3
votes
Figure out transaction ID
Some wallets have a function called something live "View on block explorer". For Electrum, you can see it if you right-click a transaction.
This will take you to a website on which you find your ...
- 3,224
3
votes
Is it only out of sheer luck that all my "txid"s are unique? How should I handle multi-vout transactions?
Why has none of them ever used more than one vout?
If each of your transactions only sends Bitcoin to one receiver, then there's going to be only one receiver output in each of those transactions. ...
- 68.6k
3
votes
Accepted
Is txid a required field on all transactions?
A txid is calculated from the transaction data by hashing the transaction (excluding the witness). It's not part of the transaction, but rather derived from the transaction. You can rely on it being ...
- 73k
3
votes
Accepted
How are TXIDs determined from the raw hex data of a block? Also, what is the coinbase transaction?
Transaction ID (TXID) are determined by a double SHA256 hash of the transaction data, but represented in little-endian.
For example, the transaction data of the coinbase transaction is:
...
- 413
3
votes
example of transaction ID in a ledger account
All Bitcoin transaction IDs look similar, regardless of the software or device used to create them
Randomly chosen example of a recent transaction ID: ...
- 25.3k
3
votes
How to compute a TXID of any bitcoin transaction in Python
That's a SegWit transaction, not all of it is part of the transaction hash preimage (see here for details). You have to exclude the SegWit parts. This Bash one-liner returns the correct TXID:
echo '...
- 1,014
2
votes
tx-malleability who re-signed the tx?
Actually, nobody else can create a valid signature for your transaction inputs, as they do not possess the private keys to do so.
When a transaction is malleated by a third party, it is not re-signed,...
- 73k
2
votes
How does TXID gets created and at which point
The TXID, the transaction ID, is a hash of the serialized (non-witness) transaction whose UTXO is being spent. It gets created at the same time as the transaction does
- 11.8k
2
votes
Accepted
Why does bitcoin-cli not show the correct TXID for this transaction?
decoderawtransaction in 0.14.2 has some issues with decoding segwit transactions. Sometimes it will decode segwit transactions as non-segwit. These should mostly be fixed in Bitcoin Core 0.15.0.
- 68.6k
2
votes
I think I found 241 Bitcoin
Before you do anything, you probably want to make a couple backups of the wallet.dat. Check that the backups are in order before continuing.
zapwallettxes only works on the start up of Bitcoin Core. ...
- 73k
2
votes
Getting the wrong txid for coinbase transactions
The hash you created is the wtxid (hash of Witness ID), not the txid (hash of Transaction ID):
For the difference between txid and wtxid, see Mastering Bitcoin ch. 7 § "Transaction identifiers".
- 4,576
2
votes
Accepted
Getting the wrong txid for coinbase transactions
The txid is the hash of transaction without segwit data. The full coinbase transaction contains the segwit data which will result in the hash that you got. However that is not the txid.
- 68.6k
2
votes
Why didn't Bitcoin implement segwit in the first place?
Why didn't Bitcoin implement segwit in the first place?
Nobody thought of it at the time. There wasn't interest in things like off-chain scaling at the time.
Why and how does non-segwit Bitcoin ...
- 51.5k
2
votes
Question about identical txids/merkle tree in Developer guide
It refers to a (practically impossible) edge case due to how unbalanced merkle trees work.
Let's say you manage to find two transactions with the same transaction ID, T1 and T2.
Now, let's build the ...
- 17k
Only top scored, non community-wiki answers of a minimum length are eligible