Question 1: Hash & MAC Security (30 Marks) In a certain network protocol, each datagram consists of a 256-bit header and a 256-bit payload. An organisation decides to store hashed datagrams for analytic purposes. These hash values need to be calculated on resource-limited devices that can only process data in 256-bit chunks. Thankfully, the devices have hardware implementations of the following cryptographic algorithms: • SHACAL, a block cipher with 256-bit keys, 256-bit input blocks, and 256-bit outputs, and • H, a secure internal hash function with 256-bit inputs and 128-bit outputs. Since the internal hash function H cannot process entire datagrams, it is necessary to design a hashing method that can compute datagram hashes based on the internally implemented algorithms. The engineers come up with the following designs for hashing datagrams: Design A: Hash separately, then XOR, i.e., Hash(datagram) := H(header) ⊕ H(payload) .
Question 1: Hash & MAC Security (30 Marks) In a certain network protocol, each datagram consists of a 256-bit header and a 256-bit payload. An organisation decides to store hashed datagrams for analytic purposes. These hash values need to be calculated on resource-limited devices that can only process data in 256-bit chunks. Thankfully, the devices […]