Fuzziness of a Key Encapsulation Mechanism (KEM)

Fuzziness is specified as a measure of the properties of the public key distribution in a Key Encapsulation Mechanism (KEM). It refers to how difficult it is for an adversary to distinguish the distribution of public keys from the uniform distribution.

"If the distribution of public keys cannot be computationally distinguished from the uniform distribution, the KEM is said to be fuzzy." [15, 16]

This definition highlights the importance of indistinguishability in the KEM, which ensures the security of the system by making it resistant to attacks that attempt to exploit non-random patterns in the public key distribution. If the adversary cannot distinguish the real public key distribution from a completely random one, the system is considered "fuzzy," thus ensuring its robustness.

Fuzziness contributes to stronger cryptographic guarantees and prevents potential weaknesses in the system from being easily detected by attackers.