Remove older versions of Zcash?

[tsusanka]

In Zcash we currently support both tx.version 3 and 4. 3 should be Overwinter, 4 Sapling. Does it make sense to support both or is one of them obsolete?

We could simplify a few things if we could remove one of the versions. See sign_tx/zcash.py for some context.

@ca333 I believe you did some zcash contributions to our firmware any chance you could shed some light into this?

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Also should we call the class Zcash instead of Overwinter?

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Related to #617

[prusnak]

AFAIK we can nuke tx.version==3 and we can even put hard check whether tx.version==4 for Zcash. I think Komodo is also on version 4 already.

[tsusanka]

Since we are now streaming prev tx we need to support also legacy transactions. So it seems we won't be able to do this anytime soon? Closing? cc @matejcik

[matejcik]

nope, this issue is about removing support for signing v3 transactions.
we already dropped v1 and v2 before the refactor, I think?
to close this, we need to find out if v3 transactions are valid on currently existing Zcash-like networks.
we think not, but it would be super nice to have some confirmation from actual Zcash / Komodo / Koto devs

[tsusanka]

@matejcik I have confirmed this via email from Zcash. The v4 transaction format was required following the Sapling network upgrade. I do not know about Komodo/Koto though.

[matejcik]

From a random sampling, both Komodo and Koto chains are using v4 since last year. That at minimum means that v4 transactions are valid on the networks, and so we can safely drop v3 support, IMHO.

So let's go ahead and do this.

Heads-up for @ca333 for Komodo and @wo01 for Koto; please let us know if this would pose any problems for you.

[wo01]

No problem.

[tsusanka]

We will test Zcash as part of Freeze so nothing specific to test here.