Can fake timestamps be used to mess with Bitcoin's difficulty adjustment?

So here's something I've been thinking about could someone actually pull off a network attack on Bitcoin nodes by feeding them wrong timestamps, and use that to manipulate the difficulty adjustment algorithm? Since this is the technical section I'm gonna assume people here already know the basics of how Bitcoin mining works, so I won't go explaining everything from scratch. But the short version is that the Bitcoin blockchain depends pretty heavily on time and timestamps to link mined blocks together and figure out what the difficulty should be. Back in the early days mining was trivially easy, you could do it on a regular CPU because the difficulty was so low. So the question is: what if you could trick a Bitcoin node into thinking the current time is actually way back in the past, when difficulty was basically nothing? Could that make it easier to mine a block and pocket the block reward? To think through how such an attack might actually work, you first need to understand how nodes and blocks handle time. Worth reading this: https://en.bitcoin.it/wiki/Block_timestamp Now here's where it gets interesting. If you spun up enough Bitcoin nodes with their internal clocks deliberately set wrong, and got other nodes to connect to them, you could potentially shift the "network-adjusted time" for those victims. That value is basically the median of all timestamps coming back from the nodes you're connected to. So if enough of your fake nodes are feeding a skewed time, the median shifts too, and you could theoretically push it back to some point in the past where the difficulty algo is much weaker. So the real question is: could you actually manipulate a victim node's perception of the current time far enough to make a meaningful difference in what difficulty it thinks should apply?

That's not going to work. The difficulty is determined every 2016 blocks (~14 days). If you manage to get the time on all nodes a week behind, the difficulty will go up more (to reach an average 10 minute block time). If anything, you could try the opposite: make it look as if 28 days have passed, so the difficulty drops. But every honest node on the network will reject your blocks, so you're wasting hash power on a worthless Fork.

Relevant discussion thread, Can avarage block time calculated in every 2016 block be manipulated?. Honestly i have doubt Bitcoin Core (and other full node software) would simply accept timestamp from other node when the difference is too big.

I don't believe that any node would just accept a random timestamp from another node, however if you controlled enough nodes that the median node timestamp was altered from reality, it could be influenced potentially?

Short answer: No Longer answer: As stated above the difficulty is based on the last 2016 blocks. Altering the time will just get your nodes ignored if your timestamps of blocks you mine are too far off. The current difficulty is the current difficulty, nothing else matters. If you did manage to do a lot of oddball things and get this to work, the rest of the nodes would ignore you and you would have a fork coin. -Dave