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.