From ZmnSCPxj at protonmail.com Wed Jun 26 06:12:39 2019 From: ZmnSCPxj at protonmail.com (ZmnSCPxj) Date: Wed, 26 Jun 2019 06:12:39 +0000 Subject: [Lightning-dev] Proposal: Lightning Pre-Image Encryption Standard In-Reply-To: References: <0u_HlmMVZWjK1afW8GB8O1JebkgPhK1fZNq7HShS1Ow6EafwkWWNX4VSjSPEddwnzkY7R9NvnVlxfGHt7JV0YYkhs5ZDJqvd_3ueT1w1ocA=@protonmail.com> Message-ID: Thank you for your thought. Another idea: would it be useful to split up large data (several megabytes long) and FEC-encode it in chunks (with each chunk having a separate MAC)? That way even if some error occurs during transmission, it is possible to recover without re-downloading entire dataset. Especially, since we need to decrypt first, before we can confirm the MAC: if the MAC fails for the chunk, it's better if we can use data from nearby chunks to recover, rather than download and re-decrypt again. Or is this over-engineering? Regards, ZmnSCPxj Sent with ProtonMail Secure Email. ??????? Original Message ??????? On Wednesday, June 26, 2019 1:41 PM, Stepan Snigirev wrote: > 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 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