Re: lockable trapdoor one-way function

From: Simon Johnson (Ckwop_at_hotmail.com)
Date: 11/27/03 

Date: 27 Nov 2003 00:18:30 -0800

"Tom St Denis" <tomstdenis@iahu.ca> wrote in message news:<388xb.5881$p8C.819@news01.bloor.is.net.cable.rogers.com>...
> "Peter Fairbrother" <zenadsl6186@zen.co.uk> wrote in message
> news:BBEABDF0.3F79C%zenadsl6186@zen.co.uk...
> > Does anyone know of a trapdoor one-way function whose trapdoor can be
> locked
> > after use?
> >
> > It can be done with secure hardware and/or distributed trust, just delete
> > the trapdoor key, and prove (somehow?) you've deleted it.
> >
> > It looks hard to do in "trust-the-math-only" mode...
>
> You'd need a secret sharing PK scheme [can't think of one] where neither
> party alone has the entire secret trap door data.

> Then provided the two parties don't collude again you have achieved the
> goal.
>
> Tom

If your using RSA then you just share the decryption exponent with a
normal secret sharing scheme. Of course, you need some secure hardware
so that the recovered secret is destroyed securely after each
invocation.

Simon

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