Square Attacks on Reduced-Round FEA-1 and FEA-2

Amit Kumar Chauhan, Abhishek Kumar, Somitra Kumar Sanadhya

Abstract: FEA-1 and FEA-2 are the South Korean Format-Preserving Encryption (FPE) standards. In this paper, we discuss the security of FEA-1 and FEA-2 against the square attacks. More specifically, we present a three-round distinguishing attack against FEA-1 and FEA-2. The data complexity of this three-round distinguisher is \(2^8\) plaintexts. We use this three-round distinguisher for key recovery against four rounds of FEA-1. The time complexity of this key recovery attacks is \(2^{137.6}\), for both 192-bit and 256-bit key sizes.