Partial proof trees should be more minimal

[ZW]

PPTs don't need to include any internal nodes on the root path --- those are redundant since the customer can compute them from siblings. I'm of the opinion that the more computation/verification a client is required to do (/the less they trust exchange-provided data) the better. I think it's very unlikely anyone would write code that did no hashing and only compared the provided PPT root hash with the published one, but I still think it's a good idea to have a standard that forces them to fully verify.

This is a comment on the format/standard rather than your implementation, since (while I haven't checked) I'm sure your implementation verifies trees fully.

[Oli]

Thanks for the comment @zw. I believe my implementation gives minimal partial trees but perhaps I should be more clear about that in the README?

Here's an example partial tree my code generates for user mark:

37618, O0qtwy08oPMHEfjpoFOBgTnUcgo17IQ4DZ1CkrlzJts=
 |_ 24614, g309qCJGWjD84lKC5H4cccwAs5Ir4ZfTqWU0+qC4L3s=
 |_ 13004, lopXy09Vz58ccSzJoTZhpOirDmTzHi/yQmRSBQv9Nog=
   |_ 9901, MqUodwm3N3TBX+7B0vA86ZSALr4XTQ0PXwws8ZjoOFE=
   | |_ 12, srapJ4u2VDM17wW0Ur3YS3zAJmrxUW/e18ccO6a9P3w=
   | |_ 9889, kpmqyLw62rNlIgjfSooU1VhrQVaCki7IFPK8gwU3rKM=
   |   |_ 9427, AkZ0c4EJySn/4skTjNrlFRPGKU9cmOJTowfQ9yEW7HY=
   |   |_ 462, mark, 0.6053108072374016, WyYL612nWZjm9qElz6EQ9bJD9LIfhUOZnugunfgDViU=
   |_ 3103, 3gMfnONog/c/t8+VZ8qbumq4JqivKmoArswe2HZPcao=

Edit: Oh I see what you mean...
9889, kpmqyLw62rNlIgjfSooU1VhrQVaCki7IFPK8gwU3rKM=,
9901, MqUodwm3N3TBX+7B0vA86ZSALr4XTQ0PXwws8ZjoOFE=
13004, lopXy09Vz58ccSzJoTZhpOirDmTzHi/yQmRSBQv9Nog= and
37618, O0qtwy08oPMHEfjpoFOBgTnUcgo17IQ4DZ1CkrlzJts= could be computed by the client?

I do double check that in my verification code but it's true that these nodes could be omitted from the published partial tree.

[Oli]

Good catch @zw. I have removed any information that can and should be computed at verification time. A partial tree now looks like:

 |_ 24614, XjUIfej5Vxd3iu9BXCoJJI7hVAQRrg0gTukaypRzxDU=
 |_
   |_
   | |_ 12, NncluiYssLFglDr21RrRlmOHkn7XpVflFDycoQJdWOM=
   | |_
   |   |_ 9427, Tijifd355WjyUdYDg/WUixo07wzNEGmXtx63VJNxff0=
   |   |_ 462, mark, 0.4003799057099968
   |_ 3103, Kz0j/ebNpCvHcwRk31STdWjqngIeMKNdBxG39GY2gtU=

Thanks.