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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Presenting a BIP for Shamir's Secret
Sharing of Bitcoin private keys
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On Sat, Mar 29, 2014 at 7:28 AM, Watson Ladd <wbl@uchicago.edu> wrote:
> This is not the case: one can use MPC techniques to compute a
> signature from shares without reconstructing the private key. There is
> a paper on this for bitcoin, but I don't know where it is.
Practically speaking you cannot unless the technique used is one
carefully selected to make it possible. This proposal isn't such a
scheme I beleieve, however, and I think I'd strongly prefer that we
BIP standardize a formulation which also has this property.
The paper you want is
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.67.9913
There will soon be a paper coming out from some princeton folks about
refining that and applying it to Bitcoin.
You can use the secret sharing from threshold ecdsa in the
not-super-useful way where you just recombine the private key and
sign... but you can also use it to compute a secret shared signature
and then interpolate back the signature... avoiding the need for any
trusted device in holding the signature.
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