elip150: handle x-only pubkeys

[LeoComandini]

In ELIP150, descriptor blinding keys cannot be x-only pubkeys. Thus if we have a 64 hex char descriptor blinding key, we need to interpret is as a single view descriptor blinding key.

[apoelstra]

Compressed public keys are allowed, but these are 66 bytes, not 64.

You mean to say that x-only pubkeys, which are 64 bytes, are disallowed.

You also need to change your test vectors.

[LeoComandini]

You mean to say that x-only pubkeys

yes, my bad, replaced "compressed" with "x-only"

You also need to change your test vectors.

removed a forgotten println!, or did you mean something else?

[RCasatta]

utACK e6d6028

[apoelstra]

removed a forgotten println!, or did you mean something else?

You are testing 66-char hex strings, but these are uninteresting because they're unambiguously compressed pubkeys. You mean to test 64-char hex strings, which could be parsed as x-only keys but shouldn't be.

[LeoComandini]

@apoelstra

You are testing 66-char hex strings, but these are uninteresting because they're unambiguously compressed pubkeys. You mean to test 64-char hex strings, which could be parsed as x-only keys but shouldn't be.

I still don't get it,
in view_xonly_pubkey_descriptor I'm testing
ct(ab16855a17319477d4283fe5c29cc7d047f81e8ffb199e20d9be1bc31a751c4c,elwpkh(021a8fb6bd5a653b021b98a2a785725b8ddacfe3687bc043aa7f4d25d3a48d40b5))#n9uc7tzt
which now parses a CT descriptor with a view key,
but before this commit was parsing as a CT descriptor with a bare key.
Since ab16855a17319477d4283fe5c29cc7d047f81e8ffb199e20d9be1bc31a751c4c (64 chars) parses both as a x-only public key and as a descriptor private blinding key.

[apoelstra]

Oh! You're right, I misread your test. You are using the 33-byte key pk but not as the view key.

[apoelstra]

ACK e6d6028