Comment on “An Efficient Homomorphic MAC with Small Key Size for Authentication in Network Coding”

Quite recently, Cheng and Jiang [1] designed an efficient homomorphic message authentication code (MAC) scheme for authentication in network coding, and claimed that the newly proposed scheme can achieve much higher security level with a formal security proof. However, in this comment, we will point out there exists a design flaw in their proposed scheme, leading to an inherent vulnerability, and also show an inaccuracy in their formal security proof. We hope that by identifying the design flaw, similar mistakes can be avoided in future design of homomorphic MAC authentication for network coding.