112-bit prime ECDLP solved

[Zooko Wilcox-O'Hearn]

On Sunday,2009-07-19, at 13:24 , Paul Hoffman wrote:

> At 7:54 AM -0600 7/18/09, Zooko Wilcox-O'Hearn wrote:
>> This involves deciding whether a 192-bit elliptic curve public key  
>> is strong enough...
>
> Why not just go with 256-bit EC (128-bit symmetric strength)? Is  
> the 8 bytes per signature the issue, or the extra compute time?

Those are two good guesses, but no.  The main concern is the size of  
the public key.  This is why (if I understand correctly),  
hyperelliptic curves might eventually offer public key signatures  
which are twice as good for the purposes of TahoeLAFS as elliptic  
curves.  (By which I mean, the keys are half as big.)  I discussed  
this topic a bit in a subsequent message to the cryptography mailing  
list entitled "Why hyperelliptic curves?".

Actually, the computation time matters, too.  Our measurements on an  
ARM 266 MHz embedded system showed a significant penalty for 256-bit  
ECDSA vs. 192-bit:

http://allmydata.org/pipermail/tahoe-dev/2009-June/002083.html

Regards,

Zooko

---------------------------------------------------------------------
The Cryptography Mailing List
Unsubscribe by sending "unsubscribe cryptography" to majordomo at metzdowd.com