We really don't have to use signing to verify the sender's authenticity. We can use a shared secret for this. This may give us more flexibility at the expense of no automated checks.
Well done you're encouraging users to invent their own cryptography schemes. You just broke rule 1.
Of course Alice doesn't want to sign her message
Why not? Signing is not about lack of anonymisation. A key doesn't have to identify an individual. It just links a message series together.
It's about conversational integrity. - Philip On 2016-11-14 17:44, [email protected] wrote:
I didn't manage to make in time before the issue was closed. We really don't have to use signing to verify the sender's authenticity. We can use a shared secret for this. This may give us more flexibility at the expense of no automated checks. But there is a theoretic case when signing is undesired! Two people, Alice and Bob, want to rob a bank. Alice has contacts in the bank and will know in advance when the right time is. So the two decide that Alice will send an encrypted message to Bob when she knows. The message will have a trailing "Dammit! Dammit! Dammit!" string at the end. (this is our shared secret). Of course Alice doesn't want to sign her message - Bob will verify that's she by the "Dammit! Dammit! Dammit!" phrase, and if there were a signature - it would be going to be shown in court if the message gets decrypted. So, for Alice, the best option is to send an encrypted message with the shared secret appended. In other words - sending messages without signing them IS A VALID SECURITY MODEL PROVIDED WE CHECK THE AUTHENTICITY BY OTHER MEANS. For example by quoting the previous message - this is a valid shared secret! Of course, the Alice and Bob example is not a real life one, but one can easily deduce a similar case in real life, when one doesn't want to have a signature so that it's never shown in court. -- You received this message because you are subscribed to the Google Groups "K-9 Mail" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout [1]. Links: ------ [1] https://groups.google.com/d/optout
-- You received this message because you are subscribed to the Google Groups "K-9 Mail" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
