Impossible Differential Cryptanalysis of Reduced Round XTEA and TEA

Abstract

We present the impossible differential cryptanalysis of the block cipher XTEA[7] and TEA[6]. The core of the design principle of these block ciphers is an easy implementation and a simplicity. But this simplicity dose not offer a large diffusion property. Our impossible differential cryptanalysis of reduced-round versions of XTEA and TEA is based on this fact. We will show how to construct a 12-round impossible characteristic of XTEA. We can then derive 128-bit user key of the 14round XTEA with 2 62.5 chosen plaintexts and 2 85 encryption times using the 12-round impossible characteristic. In addition, we will show how to construct a 10-round impossible characteristic of TEA. Then we can derive 128-bit user key of the 11-round TEA with 2 52.5 chosen plaintexts and 2 84 encryption times using the 10-round impossible characteristic.

Cryptanalysis on Block Ciphers

“…• In 2002, Moon, Hwang, Lee, Lee and Lim [86] presented an impossible differential attack on 14 rounds of XTEA.…”

Demitasse: A “Small” Version of the Tiny Encryption Algorithm and Its Use in a Classroom Setting

“…They do give a truncated differential attack against a 17-round version of TEA based on an 8-round truncated differential characteristic. Moon, et al [13] had earlier given an impossible differential cryptanalysis of 11-round TEA based on a 10-round impossible differential characteristic. It would be interesting to see how these attacks play out against Demitasse.…”

Automated design of a lightweight block cipher with Genetic Programming

“…Some results even suggest that it is, in fact, weaker than its predecessor with respect to many attacks [16][17][18].…”