Information Leakage of VGF2 Structure

Abstract EN

The block cipher VGF2 was designed at Inscrypt 2009.

It was based on a new variant of generalized Feistel structure.

By checking the property of the linear permutation, we find a full round differential in VGF2 with probability 1.

Since this differential cannot distinguish the correct unknown key from the wrong keys, we fail in launching a key-recovery attack on this structure.

However, we may guess half part of the plaintext without calculating the key.

And we notice that this weakness may cause insecurity in some special environments.