Task 6. Alice invented her own protocol to share message with Bob. She decided to use encryption algorithm that has following property: Enc(ka, Enc(k₁, m)) = Enc(kb, Enc(ka, m)). Protocol works

as: 1. Alice calculates ca = Enc(ka, m) where m - message, ka - key generated by Alice. She sends ca to Bob. 2. Bob calculates c = Enc(kb, ca), where k- key generated by Bob. He sends c to Alice. 3. Using the property of encryption algorithm, Alice calculates c = Dec(ka, c). She sends co to Bob. 4. Bob calculates m = Dec(kb, Cb). Assume that adversary Eve has full control over a public channel that Alice and Bob use to communicate. However, Eve cannot break cryptographic problems on which encryption algorithm relies.