Designing encrypted tax document sharing with WebAuthn PRF passkeys

The author explores architectural designs for sharing encrypted tax documents in a web application without trusting the API server with plaintext data. The analysis evaluates standard server-side KMS encryption, password-derived keys, and public-key wrapping, ultimately recommending a multi-origin approach using WebAuthn PRF passkeys and a document key hierarchy. This structure ensures that a remote code execution breach on the application server leaks only encrypted ciphertext rather than readable customer data. Open article →