Questions tagged [timestamp]

Collects questions about the rules, precision, and utility of the timestamp in block headers.

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11
votes
1answer
2k views

How can an earlier block have a later timestamp?

Block #180966 has a timestamp of 2012-05-20 23:02:53. Block #180967 has a timestamp of 2012-05-20 23:02:13. How has the software permitted a later block to have an earlier timestamp than its ...
11
votes
2answers
4k views

Transactions with a wait time (using nLockTime)

I'd like to know if there are transactions that can only take place at some predefined moment. In principle, it should be possible to use the parameter nLockTime to wait for a particular block number: ...
25
votes
2answers
2k views

How does Bitcoin figure out what time it is?

Bitcoin needs to know the current time in order to validate blocks. How does it decide that? Note that I'm talking about the Satoshi client specifically.
8
votes
3answers
1k views

How accurate is Bitcoin network time?

Have any observations been made to conclude the accuracy of Bitcoin network time? It would be interesting to know if NIST or any other authority has tracked the phenomenon.
5
votes
2answers
863 views

How could a time warp attack be prevented?

jarpian explains what a time warp attack (AKA zeitgeist attack) is: This is a 51% attack where the attacker sets the block timestamps artificially to lower the difficulty, allowing him to profit ...
3
votes
1answer
352 views

How is network time enforced?

I've seen how nodes gather network time data, but how is it enforced in the blockchain? Are all of the timestamps digitally signed and included in the block as proof?
5
votes
2answers
2k views

Why the timestamp component of the block header?

What is the reason for the timestamp field in the block header? Surely the nonce should be the only property that changes? Should the nonce reset to 0 everytime the timestamp changes?
4
votes
1answer
2k views

How does a time warp attack work?

I more or less understand how an attacker (with less than 50%+1 of the hashing power) can artificially lower the block difficulty by messing with timestamps. I also understand how such an attacker ...
5
votes
2answers
248 views

Why is two hours the maximum acceptable offset for Bitcoin blocks?

As far as I understand, Bitcoin transactions include a timestamp, but the only requirement is that they don't differ for more than two hours. But why two hours? For computers that are constantly ...
21
votes
1answer
805 views

Gaming the “off-by-one” bug (difficulty re-target based on 2015 instead of 2016 block time span)?

In this forum post from Gavin Andresen he writes: Second: I've written 'discourage blocks' infrastructure: https://github.com/gavinandresen/bitcoin-git/tree/discourageblocks (code reviews ...
18
votes
1answer
2k views

Was a timejacking attack ever performed?

The timejacking attack appears to be a pretty straightforward attack to pull off successfully. I was wondering, whether it was ever performed and documented somewhere, or was it just theoretically ...
6
votes
2answers
2k views

What stops miners/nodes lying about what time a block was mined?

From what I understand, the difficulty required by the proof-of-work in bitcoin is a function of block history, specifically the average time between last ~2000 blocks, with the intention that its ...
3
votes
2answers
3k views

How do we check the time when a transaction hits x confirmations?

Consider the transaction 948a427.. which has 3341 confirmations as of now: We can see that the time the relay is received at 8:36:30 and it has one confirmation at 08:50:04 (after 14 minutes). How ...
8
votes
1answer
1k views

What prevents similar time-warp attacks in Bitcoin as happened to Verge?

Right now (may 2018), Verge (an altcoin with proof of work) was attacked by time-warp attack. More can be read here https://blog.theabacus.io/the-verge-hack-explained-7942f63a3017 What exactly ...
4
votes
2answers
912 views

Can a miner set the EXACT timestamp of a block?

I know that miners can adjust the timestamp of a block, but can they control the exact timestamp datetime (within the +-2h rule)? For example: A miner mines a block at 2013-08-08 08:01:34. Can the ...
1
vote
1answer
158 views

bc.info transactions with no timestamp

The last transaction in blocks 219882, 219888, and 219892 don't have a timestamp. And by last transaction I mean the last transaction shown in the json file. 219882 219888 219892 I find this to be ...