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Non-repudiation is the ability to prevent an identified individual from repudiating a specific action or communication associated with that individual.

2 votes

TLS with non-repudiation; what happened with 'TLS Sign'?

I don't find any draft beyond the last one (expired since June 2008). I am not aware of any existing implementation. Anyway, the draft is incomplete and inconsistent (e.g. the ContentFormat type is de …
Thomas Pornin's user avatar
59 votes
Accepted

What is the difference between authenticity and non-repudiation?

Authenticity is about one party (say, Alice) interacting with another (Bob) to convince Bob that some data really comes from Alice. Non-repudiation is about Alice showing to Bob a proof that some dat …
Thomas Pornin's user avatar
3 votes

How online document signing services guarantee non-repudiation?

Legal matters depend on jurisdiction, and there are a lot of those. However, in many of them, a signature is "legally-binding" if the signer really did it. When you sign, how you do it does not matter …
Thomas Pornin's user avatar
12 votes

When using symmetric key encryption, do we need to sign?

Encryption does not protect against malicious alterations. If you encrypt some data with a stream cipher like RC4 or AES-CTR, then an attacker can decide to flip any bit he wants on the ciphertext, an …
Thomas Pornin's user avatar
3 votes
Accepted

Does SMIME differ from TLS, PGP, DMARC signature, or a Portal Encrypted email message in ter...

If you are afraid of "snooping" then why would you use signatures ? A "snooper" is a passive eavesdropper, who wants to see the data but certainly not to make you aware that your emails are inspected. …
Thomas Pornin's user avatar
41 votes

How to achieve non-repudiation?

Non-repudiation is about having a proof that the announced author really wrote the message -- and such the proof can be verified even without the consent of the said author: the author must not be abl …
Thomas Pornin's user avatar