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As more transactions are added to the block chain, does each individual transaction (ie. I send a bitcoin to a friend) get more expensive (in terms of FLOPS) to verify and commit to the chain? If each new transaction cost does change the difficulty of verifying subsequent transactions, how does this scale?

I'd appreciate any answers, links or even location in the code where this happens. Thanks.

Reference: bitcoin wiki on confirmations

wroscoe
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As more transactions are added to the block chain, does each individual transaction (ie. I send a bitcoin to a friend) get more expensive (in terms of FLOPS) to verify and commit to the chain?

No, it does not get more expensive in terms of anything. It especially does not get more expensive in terms of FLOPS because there are no floating point operations in Bitcoin.

The only cost of verifying a transaction is that it may cause the UTXO set as a whole to become larger, and as the UTXO set becomes larger, it becomes slightly harder to pull the necessary information from it to verify transactions. It does become harder to sync the blockchain as the UTXO set grows. Otherwise there is no compounding cost of verifying transactions as more transactions are added to the blockchain.

Ava Chow
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  • So if it does get more expensive, what is the right measure (alternative to FLOPS) to use? – wroscoe Dec 04 '17 at 17:29
  • Maybe Mhashes/sec? https://bitcoin.stackexchange.com/questions/1876/what-hashing-speed-does-my-hardware-have – wroscoe Dec 04 '17 at 19:14
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    Any unit of X per second is not a unit that measures computational cost. It measures the computational power of a given machine, which is not the same thing as computational cost. The computational cost would be best represented in Big O notation which is just "units of time" where a unit of time then depends on a machine's computational power. So the cost of validating a transaction would be the sum of the complexities of the hashing operations and the elliptic curve operations. – Ava Chow Dec 04 '17 at 19:24
  • Thanks. Can you give the Big O notation estimate of how the computational cost of transactions scales with the number of transactions and/or other variables? – wroscoe Dec 04 '17 at 20:33
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    It would be O(1) (aka constant time) w.r.t the number of transactions in the blockchain. This means that the number of transactions in the blockchain as no effect on the computational cost of validating another transaction. The only things that effect a transactions validation are the things contained within the transaction itself. – Ava Chow Dec 04 '17 at 20:51
  • Sorry for being dense here but I'm missing something. Why is/was the bitcoin community concerned about making the block size bigger and thus the ledger bigger if the cost of verifying transactions doesn't scale with the size of the ledger? See #6 here https://cointelegraph.com/explained/bitcoin-scaling-problem-explained – wroscoe Dec 05 '17 at 01:25
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    Larger blocks makes blocks more computationally expensive to verify. The size of the blockchain and size of blocks is unrelated to transaction verification. It also becomes harder to sync the blockchain and more expensive to store it. – Ava Chow Dec 05 '17 at 01:27
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computational cost per transaction in bitcoin is ridiculously higher e.g. several orders of magnitude, compared to traditional payment systems. That’s why it doesn’t scale.

blockbeat
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    The question is probably misunderstood, please revise. – Junaid Shaikh Jun 08 '18 at 23:45
  • @blockbeat, I suspect you are making a logical error here. You would not directly compare transactional cost an individual person making a banking transaction (or exchange of tender) to the cost of adding a transaction to the blockchain. This is unfair because you are not considering that the cost of a transaction in the banking system is paid by the profitability of the bank through lending money (and assigning fees to your banking mistakes). That bank has employees, builds to maintain, and transactions to verify. You would have to compare all this to the cost of a bitcoin transaction. – ktamlyn Dec 17 '21 at 15:21