A White-Box Implementation of IDEA

IDEA is a classic symmetric encryption algorithm proposed in 1991 and widely used in many applications. However, there is little research into white-box IDEA. In traditional white-box implementations of existing block ciphers, S-boxes are always converted into encoded lookup tables. However, the algebraic operations of IDEA without S-boxes, make the implementation not straight forward and challenging. We propose a white-box implementation of IDEA by applying a splitting symmetric encryption method, and verify its security against algebraic analysis and BGE-like attacks. Our white-box implementation requires an average of about 2800 ms to encrypt a 64-bit plaintext, about 60 times more than the original algorithm would take, which is acceptable for practical applications. Its storage requirements are only about 10 MB. To our knowledge, this is the first public white-box IDEA solution, and its design by splitting can be applied to similar algebraic encryption structures.