Questions tagged [timestamp]

For questions relating to physical or digital timestamps, usually as part of a cryptographic protocol, logging, or auditing requirement. Please use the tag [time] for questions relating to system clocks.

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13 votes
2 answers
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TLS reliance on System Time

I'm interested to know if there is any reliance on system time (as defined by Linux or windows) when initiating a secure handshake. I'm aware that TCP typically uses a random number (RFC 1323) to ...
Nark's user avatar
  • 549
14 votes
6 answers
12k views

What is the most credible timestamp I can create for a digital file?

Is it possible to create a timestamp that is so hard to fake, that it could be used as proof or simply strong evidence in a court of law, that something was not created after a certain point in time? ...
Dom's user avatar
  • 300
3 votes
5 answers
623 views

Proving an action was done at an exact time - a posteriori

I was thinking about the way git allows to edit the timestamp on commits, and how you can rewrite (public) history that way. I then drifted from that to "can we prove someone did an action at time X ...
Jiby's user avatar
  • 143
19 votes
3 answers
38k views

Pros and cons of disabling TCP timestamps

So, lynis informs me that I should unset net.ipv4.tcp_timestamps. I know that's a bad thing because an attacker could figure out which updates that require restarting the machine I haven't applied, or ...
Parthian Shot's user avatar
9 votes
4 answers
2k views

What good, standard digital signature / timestamp verification clients are widely or easily deployed?

I'm looking for a good way to publish data along with a digital signature (and ideally a timestamp) which is as easy as possible to verify via software run locally on public data. For example, imagine ...
nealmcb's user avatar
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5 votes
1 answer
3k views

Is there any functional distributed timestamp server available? If not what about this homebrew solution?

Objective A secure Arrow of Time with unpredictable future behaviour to stop attackers or DDoS BotNets from pre-calculating proof-of-work and other gateway protections for P2P/F2F. A distributed ...
LateralFractal's user avatar
39 votes
2 answers
3k views

How to prove that a file was not created in advance

Sometimes we need to prove that a file was not created in advance - a good example is warrant canaries. The person releasing them may have been forced to sign the file with a future timestamp. For ...
Samuel Shifterovich's user avatar
38 votes
9 answers
26k views

How to prove a picture was taken before a certain date? [duplicate]

I need to prove that all my pictures were taken before a certain date. Is uploading them to Picassa, Flickr or a similar service a good way to achieve such timestamping?
nadia's user avatar
  • 413
11 votes
2 answers
4k views

How do systems protect against a stolen code-signing certificate after the certificate expires?

Imagine this scenario: 1st December 2014 - a certificate is stolen and used to sign malware with 2014-12-01 timestamp. 15th December 2014 - the certificate is revoked. Malware will be prevented from ...
micro-maureen's user avatar
9 votes
3 answers
1k views

On-line cryptographically signed date/time?

I’m looking for a source of on-line cryptographically signed date/time. I do not need a full timestamp service, as I am happy with the information « date/time was that », without a link to a challenge/...
fgrieu's user avatar
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6 votes
2 answers
3k views

What are the real-time applications of long term digital signature with timestamp

I want to know the real time applications that uses digital signatures with timestamps. Specially I am interested to know the applications where we can trust an old signed document which is now ...
Naveen Kumar's user avatar
5 votes
1 answer
970 views

Trusted Timestamping Scope and Real-World Uses

What security assurances does Trusted Timestamping based on Cryotography provide? What are the real-world uses of Trusted Timestamping?
Chris Smith's user avatar
5 votes
2 answers
2k views

Does x509 have an "issued at" timestamp? Can you tell when an x509 certificate was issued?

The JWT Spec (RFC 7519) has an issued at field ("iat"). Does x509 have any analogous value? I see a Validity field, but nothing else time related.
jtpereyda's user avatar
  • 1,600
5 votes
1 answer
307 views

Random padding in hash functions

In this answer, it was recommended that you add random padding when hashing messages for a trusted timestamp, such as for predictions, in order to avoid dictionary and brute force attacks (at least ...
Daniel H's user avatar
  • 153
3 votes
1 answer
727 views

Signature and Timestamp for Long Term Document Archival Question

I have a PDF document intended for long-term (many years, maybe decades) archival which I would like to digitally sign with my personal certificate to ensure its integrity. As far as I understand, I ...
Petr's user avatar
  • 131
3 votes
1 answer
1k views

How to handle CRLs correctly in long-term electronic signatures?

What is a recommended way of handling CRLs in long-term electronic signatures (specifically the CAdES-A)? The problem I see is in that CRLs are not protected against modification (they are plain text, ...
xarx's user avatar
  • 143
2 votes
1 answer
4k views

Expiring Decryption Key

So, I'm just a programmer -- I don't know much about cryptography so bare with me and my lack of knowledge in this realm. But essentially, I'm wanting to cache data that could be potentially volatile (...
Full Metal's user avatar
1 vote
1 answer
292 views

Keeping signatures valid even after the private key has been compromised

If I understand the topic of digital signatures correctly, you sign a message via hashing+encrypting it using your private key. Then, if a private key is compromised by an attacker, she could sign ...
Giuseppe Crinò's user avatar