In this video I outline how bitvm works and illustrate how we can use it to run programs written in Assembly on bitcoin bc1qefhunyf8rsq77f38k07hn2e5njp0acxhlheksn
it's not "fully turing complete" because there is a limit on how many cpu cycles this cpu can run for. It's a large limit, somewhere on the order of 2^128 cycles, which is far more cycles than any cpu has ever run. But it is technically a limit, so this cpu is not "fully turing complete" and is guaranteed to halt eventually. Just long after the death of the universe.
Besides every program being guaranteed to halt eventually, another factor is this: the two parties agree on the program up front, and the challenge period limits how long the prover has to run it. So if the prover for some wild reason agrees to run a program that doesn't halt quickly, the verifier can initiate a challenge to prove the end state, and then the prover will simply lose his money when he can't get the program to terminate before the challenge period expires.
I question whether *this* cpu can do a lot but it's really just a proof of concept one thing I want to do with bitvm is build a bridge to a sidechain, so you can deposit to it and withdraw from it without needing to trust a federation or a central third party. Then the sidechain can be *designed* for complex computation and bitvm can sort of just "get you there and back."
On 43:20 . It was said that scripts take 50 bytes, and 32 transactions are needed to run the program. This means 50 bytes multiplied by 32, and multiplied by 100s/vB, you will probably get 160'000 sat commission, i.e. $70. Or did I misunderstand and the correct answer is 50 bytes divided by 15 current scripts and multiplied by 32 future scripts = 107 bytes, 107 bytes multiplied by 100s/vB = 10700 sat commission ($4.68) ? На 43:20 . Было сказано, что скрипты занимают 50 байт, а для запуска программы нужно 32 транзакций. Это значит 50 байт умножить на 32, и умножить на 100s/vB , наверное получится 160'000 sat комиссия, т.е. $70. Или я неправильно понял и правильный ответ, это 50 байт разделить на 15 нынешних скриптов и умножить на 32 будущих скрипта = 107байт, 107 байт умножить на 100s/vB = 10700 sat комиссия ($4.68) ?
your $70 estimate is closer. But I underestimated the script sizes. Scripts involve 6 hashes and 3 preimages, each of which are 32 bytes, so that's 288 bytes right there, and there is also a hash/preimage pair used to unlock a specific tapleaf (so that's an additional 64 bytes for 352 bytes so far), and there are also 2 pubkeys (32 bytes apiece) and one signature (64 bytes) for 448 bytes, plus about 40 to represent the input and 40 to represent the subsequent output, 4 to represent the timelock, and 4 to represent the version number. So you're at about 536 bytes per transaction, and there are 32 of them if the "unhappy path" is triggered. 536 * 32 * 100 = 1,715,200 sats as an effective transaction cost if the unhappy path is triggered, i.e. $738.88. It would be unwise to use a bitvm contract collateralized with less than that amount because you could not be sure you could get all of your challenge transactions mined in cased of a dispute.
@@highlevelbitcoin This is intellectually challenging and fascinating, but I'm just not sure how practical this actually is, if to prove fraud it's going to be that expensive to claim your money. I wonder how Ethereum handles this and if it is more efficient? Plus we're seeing much higher bitcoin fees with Ordinals and Runes being implemented!
