Questions tagged [timestamp]

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

Filter by
Sorted by
Tagged with
26
votes
9answers
4k views

Why don't the timestamps in the block chain always increase?

The timestamps starting at block 145044 are: 145044: 2011-09-12 15:46:39 145045: 2011-09-12 16:05:07 145046: 2011-09-12 16:00:05 // ~5 minutes before prior block 145047: 2011-09-12 15:53:36 // ~...
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.
21
votes
1answer
832 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 ...
19
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 ...
12
votes
0answers
2k views

How can an earlier block have a later timestamp? [duplicate]

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
5answers
3k views

how can I insert an arbitrary sha256 hash into the blockchain?

If I want to prove that I wrote a particular document before a certain point in time, it would be sufficient to generate the sha256 hash of the document and somehow arrange for that hash to appear in ...
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: ...
10
votes
2answers
324 views

What are acausal blocks?

In this forum post the poster (2112) writes: It is my understanding that at least Eligius pool isn't a "honest node" and intentionally produces acausal blocks (or at least as close to ...
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.
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 ...
7
votes
3answers
4k views

What format is the time of a Bitcoin transaction stored in?

This may be a very simple question to answer, but I haven't been able to quickly find it. Regardless, if you were to deconstruct a transaction in the blockchain, and pull out the time value of the ...
7
votes
1answer
2k views

How is locktime enforced in the standard client?

I am trying to study the locktime feature of transactions ( https://en.bitcoin.it/wiki/Protocol_specification#tx ). I have created some raw transactions in the testnet with different locktimes, but, ...
6
votes
2answers
235 views

Can a blockchain from the future be synchronized today?

If one or a few computers with blockchains from a future time line were connected to the Internet today, what would happen? This other question in Worldbuilding focus on possible consequences, but ...
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 ...
5
votes
2answers
204 views

Does Cryptocurrency really need timestamps?

Bitcoin is supposed to be a clock on it's own right so it always felt sketchy to me that outside time is referenced. Could bitcoin be aware of it's own block interval through something like uncle ...
5
votes
1answer
495 views

From where does the 2 hours limitation on bitcoin time stamp come?

Bitcoin wiki says that: A timestamp is accepted as valid if it is greater than the median timestamp of previous 11 blocks, and less than the network-adjusted time + 2 hours My question is why 2 ...
5
votes
2answers
257 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 ...
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?
5
votes
2answers
413 views

Is Bitcoin a decentralized time-stamping authority?

Can Bitcoin/blockchain be thought of as a decentralized time-stamping authority (TSA)? Is there true consensus in the Bitcoin network on a mined block's time, or just that the block was mined?
5
votes
1answer
387 views

Getwork - can the miner increment timestamp?

When requesting getwork from bitcoind or a pool, the miner is expected to be incrementing the nonce value of the block, but can it also increment the timestamp value, or would such tempering cause a ...
5
votes
2answers
882 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 ...
5
votes
2answers
4k views

The role of timestamp

In Satoshi’s original paper, it is written that “we need timestamp to prevent double-spending”. However, I think timestamp is unnecessary, because every block has a previous block hash and merkle ...
5
votes
2answers
2k views

Are timestamps in transactions trustable?

I need to properly segment transactions by time. Are timestamps in transactions trustable? Can these be forged? I'm not sure if transaction timestamps are part of the protocol, but I'm particularly ...
4
votes
1answer
548 views

January 19th, 2038: RIP Unix Timestamps

Is there a plan in place for when the inevitable 32-bit overflow of Unix timestamps occurs? How much will this impact existing blocks that are timestamped with Unix Epoch times?
4
votes
2answers
981 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 ...
4
votes
1answer
2k views

where do the timestamps on blocks come from?

A stork brings them... or... One of the basic principles on a dist. system is lack of a global clock. So how are the timestamps assigned to blocks, by the machine that mines it? Couldn't it just ...
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 ...
3
votes
2answers
506 views

Why does the median-past time average the last 11 block timestamps and not the last 12?

As described in BIP-113. Wouldn't the last 12 blocks bring us closer to a one-hour offset (ie 120min, midpoint 60)?
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 ...
3
votes
1answer
862 views

How does timejacking enable double spending?

http://culubas.blogspot.com/2011/05/timejacking-bitcoin_802.html I went over this blog, but I am still not clear how double spending is achieved by this attack. From what I read, the attackers submit ...
3
votes
1answer
663 views

Ripple ledger time format?

I am wondering what is the format used in Ripple ledger time? For example, one of the most recent ledgers had close_time of 447299110. I initially thought it was UNIX time, but the current time was ...
3
votes
1answer
132 views

Why do testnet blocks have future timestamp?

I am playing experiments with testnet blockchain, and it seems like the best block is always set about 2 hours into the future. For example, now, the block has timestamp 90 minutes into the future. I ...
3
votes
1answer
357 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?
3
votes
2answers
1k views

timestamp different block explorers are not the same

I'm kind of confused why the timestamp of a block is different when checking different block explorers. I think normally this is the time the block was found, no? So, when I check a transaction in ...
3
votes
1answer
504 views

Rewriting the entire blockchain: is it possible to spoof block timestamps of a privately mined chain?

According to fork.lol and Pieter's bitcoin.sipa, it would currently take ~200 days for an attacker with 100% of the current hashpower to rewrite the entire btc blockchain. My question pertains to how ...
3
votes
0answers
189 views

Block 620826 is 1 second before block 620825? [duplicate]

How does that happen? Obviously the miner of 826 built his block on top of 825, but why is the time 1 second earlier?
3
votes
2answers
719 views

blockchain.info transaction timestamps set into the future

There seem to be some irregularities with Blockchain.info's transaction timestamp (aka Received Time) for a set of blocks. The transaction times are recorded with unix timestamps well into the future ...
2
votes
3answers
95 views

Is there a way to see the precise time of when a transaction was sent out?

I'm a developer. I'm not really knowledgeable in bitcoin development, yet. Say, I'm using Electrum wallet. I share an address with someone. The thing is that I need this someone to pay a certain ...
2
votes
1answer
601 views

How is PSZ Timestamp encoded in Bitcoin core code?

In Chainparams.cpp of the Bitcoin Core source, the encoded PSZTimestamp is as follows ...
2
votes
1answer
751 views

Bitfinex get credits and convert timestamp to JS Date

I'm fetching my active credits in BFX and trying to discover when I'll have my funding back. This is a response example: /v1/credits [{ amount: "294.4316181", currency: "USD", id: ...
2
votes
3answers
146 views

Can the Bitcoin network be used as a timestamping service?

Does the Bitcoin protocol provide means to add some freely definable data to transactions such that a small transaction could actually be used to timestamp arbitrary data?
2
votes
1answer
26 views

Are there performance implications using the “timestamp” property of ImportMulti in the following way?

Based on the Developer Reference for importmulti, it seems the the timestamp property is purely used to determine how far back to rescan. If I have, say, 100 addresses and I simply set all of their ...
2
votes
1answer
76 views

Finding the timing of blocks, afterwards?

I understand that the timestamps on blocks are not fully accurate. Given only that information, it's efectively impossible to do retrospective analyses of timing of blocks. (For example, this; http://...
2
votes
1answer
609 views

Are transactions verified in chronological order?

I've seen that blocks include timestamps which are updated "Every few seconds", but who updates the timestamps, and are the timestamps used to verify transactions in chronological order? If a block ...
2
votes
1answer
939 views

How to calculate block generation time from block's data?

I'm working on paper Double-Spending Attacks on Fast Payments in Bitcoin. And I see they give out the result : block generation time is approximately 10 minutes (9 minutes and 54 seconds), the ...
2
votes
1answer
141 views

Bitcoin QT computer time

Bitcoin qt says my computer time needs to be correct for it to work properly. My time is right to the minute, but not the second. Will this cause a problem?
2
votes
0answers
78 views

Source for accurate block timestamps?

Is there a source of historical data which assigns a relatively consistent and accurate timestamp to each block? This might take the form of a server having precisely logged when they first heard ...
1
vote
3answers
89 views

What prevents DoS based on near-valid block timestamps?

Upon receiving a newly mined block, the block timestamp validation is performed here: https://github.com/bitcoin/bitcoin/blob/master/src/validation.cpp#L3263-L3270 Q1: As for the second check (block ...
1
vote
1answer
84 views

What does best block time mean in wallet.dat

I have a wallet.dat file that states: Best block at time of backup was 42603 (0000000013136bd812212959a15ef0ea0f084ee2c64e2f7f0e127d198f67a37f), mined on 2010-02-26T00:36:08Z Does that mean that one ...
1
vote
1answer
139 views

Why do we need two transactions for CommitCoin scheme

I am studying BitCoin recently. I noticed a method called CommitCoin for secure timestamping. It requires two transactions to send coins back with the same randomness so that others can compute the ...