I respectfully request that for accepting ZEC donations, the Tor Project create a shielded-only address in the new, no-“trusted setup” Orchard shielded value pool. (I specify “shielded-only”, because the new unified address format can combine both shielded and transparent in a single address.) At present, TPO has only a transparent address.
Tor’s cryptocurrency donation page (onion) (archival snapshot—onion):
The text of this post was intended for a PM addressed to the following staff. Discourse won’t let me as a “new” user make any PMs, even to staff. I know that you are busy people; please excuse this terse explanation up top about why I am addressing each of you:
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@smith: This is a discussion of Tor Project fundraising.
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@isabela: As explained below, I think the Tor Project’s experience setting up a shielded-only donation address would be a great topic to discuss at Zcon3:
(I don’t know when that will be, or any other details: As a stubborn Tor user, I cannot currently see the Zcash Foundation’s website.)
Foremost, as a Bitcoiner, I must applaud your use of a self-hosted BTC Pay Server—even a BTC Pay onion! Tor has strong support in the Bitcoin community. Accordingly, for my first post on your new forum (I’ve posted to the Tor Project’s mailing lists before), I chose symbolically to discuss a little-known fact that I think should receive wider attention:
(Aside, for enhanced privacy, BTC Pay Server supports on-chain Payjoin and off-chain Lightning. At a glance, neither of those appears to be enabled here. I understand that enabling them entails additional administrative burden, whereas relatively few people may have wallet support on the donor side. I hope that someday, the Tor Project will find that worthwhile.)
I am also a longtime, die-hard Zcasher, who yearned for zero-knowledge proof privacy ever since Zcash’s antecedent, Zerocoin, was proposed for Bitcoin in 2013. Naturally, I want to use Zcash with Tor. I had been running zcashd with onlynet=onion from the start.
As a part of my effort to get the Zcash Foundation website to stop blocking Tor—and even more importantly, to urge Zcash to add support for onions, as it currently lacks—I decided that I should start constructively helping to promote Tor usage in the Zcash community. While making some preliminary preparations for that, I noticed that the Tor Project only accepts ZEC donations via a transparent address.
@isabela, I think that now is a great opportunity to get these privacy projects better aligned on their shared values and shared goals for promoting privacy. @smith, no promises here—but I think that if I start actively to promote Tor usage on the Zcash Forum, I will need some practical examples of how people can use Tor with Zcash. Besides tipping the volunteer author of long posts loaded with informative links, I can’t think of a better didactic illustration than suggesting that people donate fully-shielded ZEC to the Tor Project. 
As a matter of principle, I usually try to conduct all such discussions in full public view. But here, I don’t see the harm in trying to work up a nice surprise for both communities. I know that the ECC people worked hard on the recent “Orchard” upgrade. I know how many Zcashers are distraught at the relatively low usage of shielded ZEC from launch in 2016 to the present; the lack of use of Zcash’s privacy features has been a longtime pain point.
A Tor Project shielded-only donation address is just the kind of thing that may seem trivial in the big picture, but it could make a splash if introduced the right way. It is symbolic. People would be excited.
Wherefore my request.
Blockchain transparency is a bug, not a feature.
To avoid any FUD about this: As I mentioned in my public post on the Zcash Forum, I observe that the Tor Project has an XMR donation address; thus, I presume that they must already have in place any necessary procedures for auditability and accounting with selective disclosure of view keys. Similarly, credit card transactions are not publicly visible. And your awesome BTC Pay Server has features that could make it more difficult to tell if people are donating BTC to Tor.
Upon a cursory search, I do not see any single page with clear, current documentation of Zcash’s extensive viewing key cabilities; I find only an outdated blog post from the Sprout era. Zcash has Full Viewing Keys (FVK) and Incoming Viewing Keys (IVK), plus other fancy selective disclosure features. If you need any help with this, please let me know; I myself don’t have much experience with viewing keys (little need thus far), but I could try to find information or to connect you with the right people. If you ask on the Zcash Forum, please feel free to at-mention me (also @nullius there) so that I see the thread.
Zcash shielded transactions have encrypted memos, which perhaps may be useful for collecting donations. If a donor needs to send identifying information to the Tor Project, such as for tax deduction purposes, the report can travel together with the money. However, I urge caution here: The memos are irrevocably parts of the transactions. If auditors may sometimes need to see the transactions but not the donor identities, or may need to see both sets of information but retain only one of them, if may be better to make reports off-chain as done by the current web form.