Questions tagged [transaction-verification]

Refers to the process of checking the validity of transactions.

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How do nodes validate that a UTXO in a new transaction is unspent?

Does it check every block in between where the UTXO first appeared and the current time to make sure it didn't get spent then? Or is there some other caching or other method to make the check faster?
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How can a reciever verify that transaction data was not altered by 3rd party?

My scenario: My web server: - Generates private and public, and a wallet address from the public key for a user website account - Server can not connect to the outside (Can not connect to the Bitcoin ...
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At what block height may locktimed transactions get included?

Transactions with outputs whose sequence is smaller than UINT_MAX are interpreted as locked until the timestamp or block height specified in nLockTime is reached. Specifically regarding the block ...
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Get transaction data from full node

Background Information I am building an application that requires the ability to query any bitcoin full node (from a python script using raw tcp sockets) in order to read the OP_Return value listed ...
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1answer
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Can attackers change transactions during a 51% attack?

If in a 51% attack transactions can be reversed, isn't it possible that the chain with more hash rate also changes transactions (for example if x sent 5 btc to y, they would change it to x sent 500 ...
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How to verify locking and unlocking scripts?

I've selected an arbitrary transaction id and retrieved its associated transaction details using the blockcypher explorer as follows: from blockcypher import get_transaction_details ...
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Verify Bitcoin Transaction

Following the great post [Redeeming a raw transaction step by step example required, I came up with code below but the verification failed. // pubkeyBytes, len: 65 // ...
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Sent BTC from Coinbase, blockchain explorer says Confirmed. Is recipient lying or could something else be the issue?

Sent BTC (approx $500) from Coinbase, Blockchain explorer says Confirmed. Is recipient lying they have not received or could something else be the issue such as his wallet? Recipient says it could be ...
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What stopping miner from altering value in transaction to increase transaction fee?

I'm learning bitcoin through this book "Mastering Bitcoin, 2nd Edition by Andreas M. Antonopoulos". I'm at Chapter 6 "Transactions". Here is my doubt: Example there is node A, received transaction ...
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Not able to Spend 2-2 MultiSig UTXO

I created 2-2 Multisig Account 2NECouPA4UVNMzX1K7kekc4W3VudDhMdFkM from msrFNhKwLu9GrT3hFoizz21xEwJ61xMsym and n1NPFEJHBA8j63B5dgJ3aQcufA8VmrN27U, I tried spending UTXO from this account but got an ...
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217 views

How to tell if a transaction is valid?

So I have been reading up on bitcoin and blockchain for awhile now, but I have yet to fully understand it. I understand that bitcoin leverage on DLT, which uses cryptography to verify transaction. ...
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Clarification on the script P2SH, how is executed to Bitcoin core?

This question is a continuation of the my post yesterday. Today I have a question on P2SH execution so, an example of the script should be this OP_0 <A Signature> <B Signature> OP_2 <...
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Bitcoin check if the transaction is valid

When a node receives a new transaction, that node will check if the one broadcasting the transaction has enough coins to initiate it. Bitcoin follows a UTXO model, therefore the node has to check in ...
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281 views

How does this simple script use the OP_CHECKSIG opcode?

I have this Script P2PKH <A Signature> <A Public Key> OP_DUP OP_HASH160 <A Public Key Hash> OP_EQUALVERIFY OP_CHECKSIG The bitcoin.org documentation say this The entire ...
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Bitcoin Signature Verification

I am trying to implement the OP_CHECKSIG opcode of Bitcoin and verify whether a signature is valid or not. I have the signature that I recieve from the transaction data and the public key(the hex ...
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1answer
637 views

Verifying a bitcoin Signature and what is the transaction data that is signed?

Given a bitcoin transaction where it is able to redeem it's UTXO's, how can I verify in Java if the signature is actually a valid signature or not. I was trying to use the Bouncy Castle library where ...
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1answer
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How does OP_CHECKSIG work

Hi I am learning bitcoin and learning how scripting works and how to use P2PKH. I was wondering how does OP_CHECKSIG work. I want to understand what is the data that the private key signs to create ...
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1answer
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How to prevent double spending Bitcoins?

If I create a transaction, my node will check my UTXO's and if i have enough BTC to do this transaction it will be mined. So let's say I want to spend 12 BTC to Anna. The System will check if i ...
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Ironically, encryption is not an important part of bitcoin (?)

The above statement is taken out of a book which I've been reading: Mastering Bitcoin 2nd Edition. ...as its communications and transaction data are not encrypted and do not need to be encrypted ...
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431 views

What happens to transactions included in extinct or invalid blocks?

I have read that a block contains several transactions. An attacker can forge fake a block. The blockchain is safe because the system will choose and keep the longest chain. So the fake block will ...
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Is verification of a blockchain computationally cheaper than recreating it?

One of the advantages of cryptocurrencies like Bitcoin that is often repeated is how hard it should be to manipulate past transactions. The reason that is often stated is that you would have to re-...
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1answer
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How exactly do transactions work?

When I search for transaction in bitcoin I am able to find explanations which tell me that there are e.g. two persons A and B and A wants to tranfer a number of bitcoin to B. Imagine A wants to pay 2 ...
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What does "Green address verification" mean in the context of transaction validation?

I am only new to Bitcoin and I would like to know what a "Green address verification" is. I have an Electrum wallet ver 3.3.6 and I think the term is being used in the context of faster transactions ...
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Bitcoin transactions validation process

I have a general understanding of building blocks. But am hoping someone can fill in the details/gaps. Also, can you correct if something is not right? Thanks. Scenario: Bitcoin transactions are ...
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1answer
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How can I calculate/estimate how quickly a machine can verify transactions on the blockchain?

If I have some machine with particular specs in mind (processor/memory/bandwidth), how can I estimate how quickly that node can download and verify transactions? In a quick search I wasn't able to ...
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Can anyone initiate a Blockchain transaction into the mining pool?

Let's say user A has public key P and corresponding private key P'. Can someone else initiate a transaction for public key P with some wrong private key, let's say P''? Once this goes to the memory ...
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If I set assumevalid=0 after syncing the blockchain will Bitcoin Core go back and validate historical blocks?

I originally synced my node using the Bitcoin Core default assumevalid value. If I set -assumevalid=0 in bitcoin.conf and restart my node, will my node go back and validate historical blocks?
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Following SegWit implementation, is BIP-146 signalling and implementation still on the docket?

Is BIP 146, which defines using the low S value, still on the docket to be signalled and implemented given that SegWit fixed the txid malleability issue by moving the witness outside the transaction? ...
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Besides transaction validation, are there any other uses of the Script language in Bitcoin

Script's stack operations are used to validate signatures and scripts of transaction inputs and outputs. Is Script also used to validate block, network, or any other data? Seem like there are a lot ...
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Checking if a receiver has enough coins

How do miners verify the blockchain transaction history to check if the sender has enough money if the address can be changed at any time?
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How miner makes sure that a transaction he picked up from mempool is actually valid? [duplicate]

I have read and searched enough about the roles and responsibilities of miners here; For example: Does the miner first validate transaction before doing POW or he does not validate at all ? Does a ...
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1answer
120 views

Why are only specific transaction types accepted into the mempool?

In the Bitcoin Mainnet, only specific transaction types are accepted: Bitcoin uses a scripting language to specify (and satisfy) the encumbrances, thereby allowing a whole host of transaction types....
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190 views

Where is sum(vin) > sum(vout) check in Bitcoin Core?

I'm searching the function that validates a transaction according to Protocol rules - "tx" messages especially step 14 sum(vin) > sum(vout). I found this interesting function CheckTransaction(...
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Are transactions with the same ScriptSig a security problem?

For instance while looking at the transaction stack of my address, tracing it to exchanges I use, I came across this: https://www.blockchain.com/btc/tx/...
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Indexing of transactions in the blockchain

Say we have transaction T(1) from many years ago, at block height 125001; then a new transaction T(2), consuming all the outputs from T(1), comes up around block height 568720 (that's Today). There's ...
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Bitcoin checks and balances

When a new block is created, does each block need to be validated? How does it differ from validating transactions? Why miners would waste time validating transactions and blocks when they could ...
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1answer
189 views

How to generate the digest from a raw bitcoin transaction for verifying signature of specific input?

I'm writing a stand alone process that needs to verify that a known UTXO is part of a new transaction with a valid signature. Inputs [ UTXO, raw transaction, input_number ] How do to I verify the ...
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93 views

How can block time and block size be fixed when transaction volume is constantly increasing?

As I understand it the network rejects blocks over 1MB, and block hash difficulty is set after each block is created as to keep the block time close to 10min. But if people are constantly joining ...
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On blockchain scalability bottleneck

It is often said that the major bottleneck of blockchain scalability is that every (honest) node has to process every (valid) transactions. But the progress of a blockchain is how fast it reaches ...
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1answer
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Validate 3rd party transactions on Bitcoin-qt debug window

Is there a way to validate a random transaction via transaction ID on the debug window? Imagine I want to validate a transaction between 2 wallets I don't control. I believe its possible to check if ...
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201 views

P2SH secure spending. How?

Maybe my question is stupid, but imagine that I'm trying to spend inputs from p2sh. For example, p2sh scriptPubKey looks like: OP_SHA256 ...
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637 views

Why are the inputs of Bitcoin transactions signed?

This is my understanding of what a transaction looks like: inputs: input0: txid: <funding tx0 TXID> outputID: <output ID of UTXO in the funding tx0> scriptSig: <...
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How are blocks verified?

I see in the bitcoin wiki there is something called "script" which compiles down to some bytecode to be run by a very very basic virtual machine. Does this mean that each block is actually just a ...
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1answer
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Is it posible to create a transaction output that can either be reddemed by privK of Addr A or by privK of Addr B AFTER certain blockheight?

I am thinking about how to secure your Bitcoin savings. One idea I had was to create sort of a "backup" address B for an address A which stores the bitcoins. So what I want to achieve is that you ...
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When do scripts executed?

Can anyone explain when does a script executed exactly? There are several information about "how scripts are executed" but no information about "when".
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Bitcoin transaction fee calculator

I'm new to bitcoin. Is there a website where I can type amount of BTC I want to send and type of transaction - Urgent, Normal, Economic and they give me the price in USD how much the transaction fee ...
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How does blockchain technology handle the actual transaction data?

My understanding of how a transaction is secured in blockchain, especially in bitcoin, is that the output of transaction data is locked to the recipient's address (a shorter version of his public key)....
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May it be a risk to use the origin as the change address?

Follow scenario: The balance of my origin address is 1 BTC. I'm transfering 0.1 BTC to a shop where I'm buying some goods, my wallet returns the change to my origin address. Now my origin address has ...
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How do you get Sibling Hashed Values in a Merkle Proof?

Merkle Proofs are one of the main reasons that people attribute Bitcoin's use of Merkle Trees. But I'm struggling to understand how these work in practice. Please explain theoretically as well as ...
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Reject or refuse to relay a valid transaction

Under the Bitcoin protocol, how much control does a node have on how a transaction is dealt with once received? Can a node reject a valid transaction? Can a node refuse to relay a valid transaction to ...