Fate of Ecash if RSA is cracked?

Hello,

After reading Comm. of ACM and Schneier's book about ecash,
a question arose: what if the underlying public key cryptographic
scheme gets broken somehow? Suppose, for example, that someone
discovers an ultra-fast factoring algorithm or something like that.

What would happen with all ecash that's been issued? Of course
criminals would be able to forge large amounts of authentic-looking
ecash, so banks should not be honoring requests to convert e-cash into
real cash.

I apologize in advance is this question is silly, and will appreciate your
corrections.

	- Igor.

ichudov@algebra.com (Igor Chudov @ home) writes:
> scheme gets broken somehow? Suppose, for example, that someone
> discovers an ultra-fast factoring algorithm or something like that.

This'll happen, probably sooner than later.

---

Dr. Dimitri Vulis
Brighton Beach Boardwalk BBS, Forest Hills, N.Y.: +1-718-261-2013, 14.4Kbps

Dr. Dimitri Vulis wrote:
> 
> ichudov@algebra.com (Igor Chudov @ home) writes:
> > scheme gets broken somehow? Suppose, for example, that someone
> > discovers an ultra-fast factoring algorithm or something like that.
> 
> This'll happen, probably sooner than later.
> 

Hm, how about using two public-key algorithms simultaneously (ie,
providing signatures made using two algorithms with each coins)?  This
way, if one algorithm gets broken, there would be supposedly enough time
to make a transition to another method or at least honor the issued ecash.

Just curious.

Another question: what happens to the ecash issued by a bank if it's
secret keys get stolen?

Thanks,

	- Igor.

On Sun, 2 Jun 1996 23:47:32 -0500 (CDT), you wrote:

>Another question: what happens to the ecash issued by a bank if it's
>secret keys get stolen?

	The same thing that would happen if someone were to steal the keys to
the bank, and the combination to the vault.


"Randomness is in the eye of the beholder" --Numerical Recipes
gregmi@mis.net (Greg Miller)
http://grendel.ius.indiana.edu/~gmiller/

Dr. Dimitri Vulis writes:
> ichudov@algebra.com (Igor Chudov @ home) writes:
> > scheme gets broken somehow? Suppose, for example, that someone
> > discovers an ultra-fast factoring algorithm or something like that.
> 
> This'll happen, probably sooner than later.

Why do you assume that? There are plenty of problems that are
provably not solvable in non-exponential time even if P=NP. What makes
you think this one is going to be solved?

.pm

On Sun, 2 Jun 1996 17:42:49 -0500 (CDT), you wrote:

>What would happen with all ecash that's been issued? Of course
>criminals would be able to forge large amounts of authentic-looking
>ecash, so banks should not be honoring requests to convert e-cash into
>real cash.

	As I understand it, ecash shouldn't be withdrawn until shortly before it
is spent.  If the RSA algorithm is broken, then then banks could refuse the
withdrawal (and depositing) of money as ecash.  The remainder of the money in
each users' account would have to be withdrawn through conventional methods.

	Of course all the outstanding (between withdrawl and deposit) ecash
could be a problem.
"Randomness is in the eye of the beholder" --Numerical Recipes
gregmi@mis.net (Greg Miller)
http://grendel.ius.indiana.edu/~gmiller/

US SEcret Service was always on top of criminal counterfeiting. I make 
that "criminal" distinction becaue there is allegedly a phenomenon of  
low-intensity-warfare going on, with Iran sponsoring more-or-less perfect 
counterfeits of hundred dollar bills.

Criminal counterfeiting was a dangerous game. Secret Service pretty much
knew every individuial/company who was involved in bona fide use of the
relevant papers, inks, engraving/printing equipments, etc., and anyone
ordering any of this stuff from the very limited number of suppliers, was
placed under watch. It's a small world out there, kids.

Alan Horowitz <alanh@infi.net> writes:
> US SEcret Service was always on top of criminal counterfeiting. I make
> that "criminal" distinction becaue there is allegedly a phenomenon of
> low-intensity-warfare going on, with Iran sponsoring more-or-less perfect
> counterfeits of hundred dollar bills.

I wonder what would happen if someone posted PostScript code for printing
counterfeit money on a color printer? :-)

---

Dr.Dimitri Vulis KOTM
Brighton Beach Boardwalk BBS, Forest Hills, N.Y.: +1-718-261-2013, 14.4Kbps