This is a smart approach to a real problem. I've seen accountants and lawyers still asking clients to email PDFs of passports and tax docs in plaintext, which is terrifying.

One thing I'd be curious about: how do you handle the key management UX for non-technical clients? The zero-knowledge property is great, but I've found that "you're the only one with the key, so don't lose it" tends to create support headaches when people inevitably lose access. Have you considered any middle-ground approaches like social recovery or time-delayed access fallbacks that maintain privacy?