Client: Support Zcash Sapling addresses in profile

[garethtdavies]

On October 28th Zcash will upgrade to Sapling. In doing so it will enable the more efficient Sapling transactions. These Sapling addresses have a different format and it isn't possible to add these new addresses to the Keybase profile.

Old style: zcA6qngiR3U7HxYopyTWkaDLwYBd83D5MT7Jb9gpgTzPLMZytzRbtdPP1Syv4RvRgHeoZrJWSask3DyfwXG9DGPMWMvX7aC

New style:
zs1z7rejlpsa98s2rrrfkwmaxu53e4ue0ulcrw0h4x5g8jl04tak0d3mm47vdtahatqrlkngh9sly

While the legacy Sprout z-addresses will continue to function after Sapling activates given the benefits of Sapling it's likely they see far greater adoption so support for them would be most welcome!

[maxtaco]

Thank you for the update, we will try to make this change as soon as we can.

[maxtaco]

@garethtdavies do you have a reference for how to consume and error-check these addresses? Details are scarce as far as I can tell, the Bitcoin Bech32 scheme doesn't seem to work out of the box.

[maxtaco]

In node, I tried this:

$ npm i bech32

bech32 = require 'bech32'
bech32.decode('zs1z7rejlpsa98s2rrrfkwmaxu53e4ue0ulcrw0h4x5g8jl04tak0d3mm47vdtahatqrlkngh9sly')

That yields an invalid checksum. This works though:

bech32.decode('zs1z7rejlpsa98s2rrrfkwmaxu53e4ue0ulcrw0h4x5g8jl04tak0d3mm47vdtahatqrlkn3pxg7n')

Similar results with Golang library I found (see this branch)

[jasondavies]

I think @garethtdavies gave you an invalid Sapling address by mistake, that's why it doesn't validate. You can validate a z-addr using zcashd, using the z_validateaddress RPC call.

Regarding validation itself: that's slightly more complicated to fully reflect what zcashd does but I will post further details here when I get a chance. You will need to check the following:

• Prefix is "zs".
• Number of words is 69.
• Check total number of bits is within the expected range when converting from base 32 to base 256.

Do you typically use Node.js within keybase for this kind of check?

[maxtaco]

That would explain it! I think this address shows up in the official Zcash docs too, see this screenshot from this URL. Also, it shows up in the official blog post. I saw the details about what's inside in the spec, but the spec was mute on what happens one layer up, aside from saying Bech32. We do some server-side node, but we're using Go on the client side. That branch above shows that I was trying this library for decoding.

[garethtdavies]

Great catch @jasondavies. Sorry for the confusion, I didn’t even think to check this and just copied from the official blog post as referenced above.

[maxtaco]

@jasondavies Are there valid sample sapling addresses published that I can test against?

[jasondavies]

I generated a few for you:

zs1x2q4pej08shm9pd5fx8jvl97f8f7t8sej8lsgp08jsczxsucr5gkff0yasc0gc43dtv3wczerv5
zs1fw4tgx9gccv2f8af6ugu727slx7pq0nc46yflcuqyluruxtcmg20hxh3r4d9ec9yejj6gfrf2hc

[maxtaco]

cheers

[maxtaco]

Thanks @jasondavies, those all worked.

[maxtaco]

https://github.com/keybase/client/pull/14472

[maxtaco]

Reader support is in master now. We're going to wait a release cycle before we enable posting of Sapling addresses. Thank you.

[jbash]

What counts as a "release cycle"? I just installed the 3.0.0 RPM and I still can't add an address.

[maxtaco]

Forgot to enable it serverside. Try it now?

[rex4539]

Still the "waiting one release cycle" message.

[maxtaco]

Sorry about that, we forgot to enable on the client side: https://github.com/keybase/client/pull/15912

Next release cycle, I apologize.