r-zakarya
1dc4f3bdb6
Measured on device: android.security.keystore.UserNotAuthenticatedException on every write. An AES key created with setUserAuthenticationRequired demands a recent authentication to ENCRYPT as well as to decrypt, and the write follows a silent sync with no prompt. The very first write only succeeded because the phone had just been unlocked - a test that passes, then stops passing. Now an RSA pair: the public half wraps a throwaway AES key with no prompt, the private half - the guarded one - unwraps it. Authentication is required at read time and nowhere else. Two documented traps handled: the public key returned by the Keystore carries the private key's constraints, so it is rebuilt from its encoded form; and that rebuild changes provider, so the OAEP parameters are passed explicitly on both sides - the Keystore defaults MGF1 to SHA-1 where the transformation name suggests SHA-256. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
