Large Primes

[Peter Fairbrother]

 Owen Lewis wrote:

>> [mailto:ukcrypto-admin@chiark.greenend.org.uk]On Behalf Of Peter
>> Fairbrother

>> 
>> Forget assymetric cyphers, if QC's come in they're gone. This means not
>> using them for anything but short-term signatures/authentication, not key
>> exchange.
> 
> You might have added that, with the current design of PK cryptosystems, also
> 'gone' is any useful purpose for the symmetric  bulk cipher.
> 

Eh? Long-term storage. Information transfer on insecure media using
pre-exchanged shared keys. To mention just two. It's the PK bit that will
have to go.

>> An otp is probably good for 100 years, but impractical.
> 
> Why so? Assume perfect randomness of key stream modified by filters to
> detect and remove the random occurrence of certain weak key streams that
> could otherwise reduce OTP to a Caesar cipher or too close thereto. How then
> is OTP good only for 100 years?

I meant that it should be good for at least 100 years, the needed timespan,
not only for 100 years. The "probably" was included because....  Time
machines? General Entanglement? God(s)? Shannon-was-wrong? Something as yet
unheard/ unthought of?


-- Peter