Integral Cryptanalysis of Round-reduced Prince Cipher

The lightweight cryptographic algorithm Prince is an intensively studied cipher in the last 3 years. In order to enhance the cryptanalysis efforts and to encourage the design of practical attacks against the algorithm, the designers organized the Prince Challenge. In this paper we introduce two integral attacks on 5-round and 6-round reduced Prince. The attacks, based on a 4.5 rounds integral distinguisher, lead to the full key recovery and have practical complexity. The 6-round attack was submitted to the second round of The Prince Challenge and was announced as winner during the Rump Session of the Eurocrypt 2015 Conference.