This is a nice scheme. Pedersen commitments + pay to point seems to be the most practical way to do it but you can generalise this paying for a decommitment idea to any commitment scheme. For example, you could do this in a payment channel with hashes if we had something like OP_CAT. e.g HTLC unlocks based on whether you can provide an r such that H(r || x) == C.
> Unfortunately that zkp already proves that C was generated based on x, so you get your timestamp for free. Ooops. :( I haven't studied zkp for circuits in general but I guess the non-interactive proofs are fiat-shamir transformations of an interactive protocol. Maybe you could just use the interactive zero knowledge protocol which doesn't have the side effect of the verifier with a proof they can give to others. LL On Thu, Sep 26, 2019 at 5:30 AM Anthony Towns <a...@erisian.com.au> wrote: > On Wed, Sep 25, 2019 at 01:30:39PM +0000, ZmnSCPxj wrote: > > > Since it's off chain, you could also provide R and C and a zero > knowledge > > > proof that you know an r such that: > > > R = SHA256( r ) > > > C = SHA256( x || r ) > > > > in which case you could do it with lightning as it exists today. > > I can insist on paying only if the server reveals an `r` that matches > some known `R` such that `R = SHA256(r)`, as currently in Lightning network. > > However, how would I prove, knowing only `R` and `x`, and that there > exists some `r` such that `R = SHA256(r)`, that `C = SHA256(x || r)`? > > If you know x and r, you can generate C and R and a zero knowledge proof > of the relationship between x,C,R that doesn't reveal r (eg, I think > you could do that with bulletproofs). Unfortunately that zkp already > proves that C was generated based on x, so you get your timestamp for > free. Ooops. :( > > Cheers, > aj > > _______________________________________________ > Lightning-dev mailing list > Lightning-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/lightning-dev >
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