rich1.0npub1t9txg5aevth45pu9hcz075tj3ch25fydn8c38wew90qjjdjv3rqq3r6cf0https://nostr.ae/npub1t9txg5aevth45pu9hcz075tj3ch25fydn8c38wew90qjjdjv3rqq3r6cf0njumphttps://nostr.ae📅 Original date posted:2011-09-13 🗒️ Summary of this message: Bitcoin's timejacking and related exploits can be fixed by overlapping block timestamps and using NTP, but new block timestamp rules are needed. 📝 Original message:Gavin Andresen wrote: > Background: > > Timejacking: > http://culubas.blogspot.com/2011/05/timejacking-bitcoin_802.html > > And a recent related exploit launched against the low-difficulty > alternative chains: > https://bitcointalk.org/index.php?topic=43692.msg521772#msg521772 > > > Seems to me there are two fundamental problems: > > 1) Bitcoin should be overlapping the ranges of block timestamps that > it uses to calculate difficulty adjustments. > > 2) Bitcoin's "what time is it" code is kind of a hack. > > > Fixing (1) would mean a potential block-chain split; before > considering doing that I'd like to consider second-best solutions. > > Fixing (2) is easier; incorporating a ntp library and/or simply > removing the bitcoin mining code from the client but requiring pools > and miners to have accurate-to-within-a-minute system clocks (or their > blocks will be "discouraged") seems reasonable to me. If you want to > produce blocks that the rest of the network will accept, run ntp on > your system. > > I THINK that fixing (2) will make (1) a non-issue-- if miners can't > mess around with block times very much then it will be very difficult > for them to manipulate the difficulty for their benefit. > The first thing I always do when I grab the source for my colo server is patch util.cpp so that GetAdjustedTime() returns GetTime() with no adjustment. But I'm the kind of guy that buys special GPS receivers because stratum 2 isn't low enough and occasionally checks ebay for caesium fountains. NTP has been around for long enough now that there is no reason for the client to screw with the clock. If the client sees different times on the network, it should issue a warning, and if it is off too far, it should give an error and fail to run (and/or peers should reject it). But that doesn't solve the whole problem, because the block timestamp checking is based on the assumption that the node is looking at the bitcoin clock rather than the, ahem, real clock. If we change the idea of network time to NTP, we will then need to write (and test!) new block timestamp rules to account for the new assumptions. I'm not sure that just fixing item 2 is going to stop the attacks found by ArtForz, et al. Some of the attacks Art pointed out are particularly bad because they change the incentive structure of the system, at least in the short term. We need to flip that back around ASAP. Also, this is going to cause problems for at least one pool operator.