Author: Mark Friedenbach 2018-01-09 12:40:30
Published on: 2018-01-09T12:40:30+00:00
Rusty Russell, a Bitcoin developer raises concerns about the flexibility of BIP 117 which is a new proposal for improving the Segregated Witness (SegWit) feature in Bitcoin. Currently, the use of altstack is considered awkward and is seen as a hack to bypass the clean stack rule imposed by segwit script version 0. Rusty suggests that there could be future improvements that will switch to a witness script version and a new segwit output version which supports native MAST to save an additional 40 or so witness bytes. Either approach would allow getting rid of the alt stack hack. Rusty also mentions concerns regarding the dropping of SIGOP and opcode limits in BIP 117. He believes that it requires more justification, particularly in terms of measurements and bounds on execution times. He suggests that it is better to limit the number of checksigs allowed in a script to size(script+witness)/64 but wanted this to come up in review rather than complicate the code right off the bat.In order to restore statically analyzability by rules, Rusty proposes that only tx version 3 segwit txs should be applied for such restrictions. For version 3, the top element of the stack is counted for limits (perhaps with a discount). The blob popped off for tail recursion must be identical to that top element of the stack (ie. the one counted above). Future tx versions could drop such restrictions.
Updated on: 2023-06-12T23:42:55.097788+00:00