2024 Asian Conference on Communication and Networks (ASIANComNet 2024)

ULBC is a SPN based block cipher, operates 64 bit state and use 128 bits key. Here we present meet-in-the-middle (MITM) attack on ULBC. MITM attack strategy proposed by Demirci and Selcuk. In this paper we partition cipher ULBC in two halves and separate key space by two independent set and observe matching between encryption of first half with decryption of second half. By this method, called MITM attack, we can reduce the key space for exhaustive search. Basic fault analysis of ULBC requires $192$ faulty ciphertext to detect full key register. Also, we provide another fault analysis method of ULBC, which requires only average $57$ faulty ciphertext to retrieve master key. Here we assume that we can induce nibble fault in after or before substitution layer to any rounds. MITM and Differential fault attack particularly exploits weakness like dependency, linearity of designing key schedule.