[Rats] Re: [lamps] Re: Re: Freshness with Nonces

[Muhammad Usama Sardar <[e-mail]>]

Hi Henk,

your short sentences seem to be missing some context. So I still don't 
fully understand what you are saying.

On 21.06.24 12:18, Henk Birkholz wrote:
> Hi Usama,
>
> you cannot check freshness or recentness. 
"with signatures alone" I guess, right?
> But if you recognize a unique signature (and remember them in "state") 
> then you can avoid replay attacks. 
Where does this uniqueness of signature come from? The only two possible 
inputs of signature are the signing key and the data. Assuming the 
signing key remains the same, the only source of uniqueness is the data. 
And that is what I mentioned below that unless some freshness context 
(such as nonce or timestamp) is added to the signing data, how can the 
verifier check the freshness?
> That is of course not always feasible, but if you can "remember" 
> nonces, you can also remember signatures - in the context of replay 
> attacks. 
I don't immediately see any benefit of storing signatures rather than 
nonces. Can you illustrate a few benefits?

Regards,

Usama

>
> On 19.06.24 21:06, Muhammad Usama Sardar wrote:
>> Hi Henk,
>>
>> On 19.06.24 20:41, Henk Birkholz wrote:
>>> for example, signatures can be used for replay attack detection, 
>>> too. I think you do not need nonces for that at all.
>>
>> I don't think that is correct. How can signatures /alone/ be used for 
>> /replay/ attack detection? Unless some freshness context (such as 
>> nonce or timestamp) is added to the data that is signed, you can 
>> replay it forever.
>>
>> Usama
>>