Proofs for confidential (hashed) usernames

Currently, adding a social media account to Keybase creates a two-way link; anyone who knows your social media username can find your Keybase username, and anyone who knows your Keybase username gets a list of all your social media accounts. In fact, once you have added a social media account, it becomes impossible to ever disclaim ownership of it, since the (revoked) proof will remain in your sigchain. This makes it a poor choice to use for private accounts, personal accounts for public figures, etc.

This is, in a way, a similar problem to the issue of NSEC records in DNSSEC leaking zone info in the name of cryptographic proof, and it lends itself to a similar solution: instead of my sigchain containing a signed statement saying "I claim ownership of the github account 'dmchurch'", it could contain a signed statement saying "I claim ownership of the github account with sha256 hash 'd140f4...a12fd4'". Anyone trying to ask the question "Is dmchurch@github on keybase" could find the answer by hashing the username with whatever functions the keybase protocol supports and checking that way, but if someone only had my keybase username, the most they'd get would be "danichurch@keybase claims ownership of a confidential github account".

This could conceivably be taken one step further, changing all social proofs in the sigchain to use hashed usernames, and the Keybase client could publish a "current list of publicized usernames" as a signed statement that exists outside the sigchain, in the same mechanism as KBFS public folders. This way, anyone that ever wants to disassociate themselves with a past username - trans individuals who don't want to out themselves by their former name, victims of abuse and stalking for whom having a past name or identity online can be a physical danger, or even just people who realized a little too late that "ShinjiIkariKissBoy34" is maybe not the right twitter handle for an IT professional - can do so simply by removing that name from the currently-publicized list.

The proposal concerns social proofs in the sigchain and a possible signed list of currently publicized usernames. Start by locating the existing social-proof and sigchain entry points; define how hashed usernames, verification, revocation, and disclosure would work before implementation. Done would require an agreed protocol design and corresponding tests.