39
votes
Accepted
How to prove that a file was not created in advance
If all parties can trust a common randomness beacon (like the NIST Randomness Beacon), this can be achieved by including a recent block from the beacon into the file along with its timestamp. The ...
- 10.9k
28
votes
Why does HTTPS not support non-repudiation?
I thought HTTPS would prove that a given content actually came from the origin, by having its contents always signed before transfer.
Since "content" is sent in both directions, providing ...
- 208k
18
votes
Accepted
Why does HTTPS not support non-repudiation?
TLS is a two-party communication protocol, and HTTPS is not much more than HTTP over TLS. Its threat model considers only two participants (the client and the server) and its goal is to secure the ...
9
votes
Accepted
Difference between non-repudiation and plausible deniability
As in any other aspect of life, one might have different information security goals in different situations. There are situations in which you want non-repudiation and there are situations in which ...
- 5,562
7
votes
Why does HTTPS not support non-repudiation?
Among other reasons, I'm not prepared to say at a protocol level that there isn't a way to say to a CGI server, "echo this content". If you don't have non-repudiation, then this is a non-...
- 1,290
6
votes
Difference between non-repudiation and plausible deniability
It seems contradictory but it's not. One doesn't have to prove non-repudiation and plausible deniability at the same time. You can deny the ownership of the message while still keeping its ...
- 6,971
5
votes
Accepted
How can HelloSign be secure without any authentication?
how could the document-signing service verify that someone who signed
a particular document really did so?
They don't. They do create a log showing the IP address of the remote computer that issued ...
- 316
4
votes
Accepted
Difference between interception, spoofing, falsification and repudiation
Here is a rundown on the example of emails:
Interception or Snooping or Sniffing
An attacker intercepts the unencrypted traffic of an email server to record and modify the content of sent ...
- 45.1k
4
votes
Accepted
Can a client prove to a third party that they sent a message to another client in a P2P network?
An interesting question, related to the topic of non-repudiation. In this case, the thing Bob wants to do is repudiate having ever received the message. Here's one way to build a system which is ...
- 52.3k
4
votes
Accepted
2fa attestation object for non-repudiation
Non-repudiation is much harder to achieve than some would have you believe. In general, a signature is tied to a key with a very high degree of confidence, but tying the key to a specific person and ...
- 15.8k
3
votes
Doesn't Authentication logically imply Non-repudiation?
Non-Repudiation is the assurance that someone cannot deny something.
Examples of authentication without non-repudiation:
Alice's credentials were/could have been stolen and used by
someone else.
...
- 31
3
votes
Accepted
Premeditated substitution of ECDSA-signed message by the signer
Is there something I miss? A documented case where what the paper describes has lead to disaster or dispute? A common mitigation?
There are certainly some attacks which have used very similar ...
3
votes
If non-repudiation is impossible why do digital signature exist
Digital signature can indeed provide non repudiation, provided that the procedure used to sign the certificat:
ensures that the private key was at any moment under exclusive ownership of its ...
- 26.9k
3
votes
Are there any reasons to add a payload signature to a REST API with mutual TLS?
I suspect this will be a big "It depends on your architecture" and so random internet people won't be able to give you a complete answer.
Off the top of my head, here's some scenarios where it might ...
- 59.3k
3
votes
Can CA certificate be spoofed on the browser level?
Technically -- yes, they could. However, there are few thoughts:
1) web page code cannot interact with browser's address bar.
2) an attacker may write a plugin/extension if web browser provides ...
- 6,431
2
votes
How can HelloSign be secure without any authentication?
My name is Alex M. and I work in API Support at HelloSign.com. Regarding the legality of HelloSign signatures, there's an explanation on why we believe our esignatures are legal on our website.
...
- 37
2
votes
Are there any reasons to add a payload signature to a REST API with mutual TLS?
In addition to the answers regarding TLS terminating on a separate system than the one verifying the payload, you heard correctly that it can help with non-repudiation even if TLS terminates on the ...
- 15.8k
2
votes
Are there any reasons to add a payload signature to a REST API with mutual TLS?
One reason for requiring both is when the API is being used on infrastructure which separates the client certification verification and the payload verification. In some environments, the checking of ...
- 27.4k
2
votes
Doesn't Authentication logically imply Non-repudiation?
The problem is that authentication isn't one thing; it's a sliding scale. On the one hand we can imagine the weakest possible authentication which is just identification, e.g. a username and no ...
- 808
2
votes
Proving authenticity of a message from a message app in case of deletion
A screenshot is just an image file.
It can be copied without any limitations. Thus having a screenshot does not prove anything.
Everyone can create or edit any file in editor. Having an image file ...
- 12.6k
2
votes
Verifiable alternative to screenshots for web browsers
Such tools would not be able to run on a client since a common client (PC, phone) is not sufficiently trusted for this - the (potentially cheating) user has too much control of the device.
It might be ...
- 208k
2
votes
Verifiable alternative to screenshots for web browsers
There is a question of trust here. As soon as you are the only provider for a document, you cannot prove that it is authentic because you could as well have forged it. So it can only be a hint that ...
- 26.9k
2
votes
Accepted
Verifiable alternative to screenshots for web browsers
Yes, this type of product exists. Both Serge's and Steffan's answers and approaches are correct and their concerns are valid, but there is another way to accomplish "proof" (if you drop the ...
- 132k
1
vote
Premeditated substitution of ECDSA-signed message by the signer
The point of the cited paper is that security analysis of a signature algorithm must look beyond the signature algorithm itself. Here, the authors demonstrate that collusion between key generation and ...
- 1,366
1
vote
Why does HTTPS not support non-repudiation?
Non-repudiation is a legal property and as such cannot be "supported" by a protocol such as TLS. The property is interesting in case of disputes which ultimately must be fought before a ...
- 315
1
vote
Doesn't Authentication logically imply Non-repudiation?
Example to illustrate the difference: imagine a cluster of nodes who all share a symmetric key. This counts as authentication because any node in the cluster knows that it came from another trusted ...
- 59.3k
1
vote
Sign a document as created with an authorized software build
You're correct in saying that embedding a key in the software is no good, because an attacker could read out the same key.
One thing that stands out as a worthwhile place to look is the (new-ish) ...
- 1,887
1
vote
Are there any reasons to add a payload signature to a REST API with mutual TLS?
Proposing an alternate to Mutual TLS...
We have had many many support problems when our corporate customers try to set up Mutual TLS with our SAAS servers. Plus there is no good solution for ...
- 599
1
vote
How to implement a digital signature for 21 CFR Part 11 for non repudiation
Note that the problem is more of a legal than technical/implementation issue. Your links above to the FDA regulations and the other stackoverflow question How to achieve non-repudiation? emphasizes ...
- 1,852
1
vote
Can I guarantee non-repudiation with this authentication protocol?
I think this depends on whether the sender and receiver can both be fully trusted not to reveal or misuse the key.
A secret known by more than one entity is less of a secret.
So to have a guarantee, ...
- 7,152
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