unfortunately FHE doesn't work like you describe. in FHE, the answer output is always indistinguishable from random noise. in fact, the "encrypted decryptor" ro

unfortunately FHE doesn't work like you describe. in FHE, the answer output is always indistinguishable from random noise. in fact, the "encrypted decryptor" routine you're describing is more or less how bootstrapping works - the ciphertext is double-encrypted to the bootstrapping key, the circuit evaluates decryption of the encrypted ciphertext to produce a fresh ciphertext against the bootstrapping key, then a key switching operation exchanges the bootstrapping key for the evaluation key. * needing certain policies to be met for decryption is the field of attribute-based encryption. * only being able to evaluate certain functions of a ciphertext to decrypted plaintext is the field of functional encryption. * the general holy grail you're describing is program obfuscation - a secure black box that evaluates an arbitrary circuit on an input. unfortunately there are strong impossibility results in program obfuscation, though there's some theoretical progress towards weaker obfuscation or much more limited types of circuits, involving extremely inefficient mathematical wizardry that's regularly being badly broken by cryptanalysis. in summary, you've confused FHE with program obfuscation, and the decryptor routine you describe is just bootstrapping.