Resilience to Distinguishing Attacks on WG-7 Cipher and Their Generalizations

The stream cipher WG-7 is a lightweight variant of the well-known Welch-Gong (WG) stream cipher family, targeting for resource-constrained devices like RFID tags, smart cards, and wireless sensor nodes. Recently, a distinguishing attack was discovered against the stream cipher WG-7 by Orumiehchiha, Pieprzyk and Steinfeld. In this paper, the authors extend their work to a general distinguishing attack and suggest criteria to protect the WG stream cipher family from this attack. Their analysis shows that by properly choosing the minimal polynomial of the linear feedback shift register for a WG stream cipher, the general distinguishing attack can be easily thwarted.