Hi ZmnSCPxj, > Does this require Bob to attempt both positive and negative sign for the y-coordinate? > Alternately we can force Sally to always use a scalar such that generated point has a fixed sign (or some other property to derive the sign of the missing coordinate).
The best would be if Sally uses the point with a fixed sign, then Bob doesn't need to try twice and can start decrypting data from stream (for example if it's a DRM key for a movie). Similar approach is used for R-encoding in Schnorr signatures, so we could use the same convention here. On Tue, Jun 25, 2019 at 10:18 PM ZmnSCPxj <[email protected]> wrote: > Good morning Stepan, and Nadav, > > Both additions seem good idea to me. > > > - Sally generates the invoice with the preimage `S` (i.e. x-coordinate > of this point to make it 32-bytes long) > > Does this require Bob to attempt both positive and negative sign for the > y-coordinate? > Alternately we can force Sally to always use a scalar such that generated > point has a fixed sign (or some other property to derive the sign of the > missing coordinate). > > Regards, > ZmnSCPxj >
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