On Security of a White-Box Implementation of SHARK

In a white-box attack context, an attacker has full visibility of the implementation of a cipher and full control over its execution environment. As a countermeasure against the threat of a key exposure in this context, a white-box implementation of the block cipher SHARK, i. e., the white-box SHARK, was proposed in a piece of prior work in 2013. However, based on our observation and investigation, it has been derived that the white-box SHARK is insufficiently secure, where the hidden key and external encodings can be extracted with a work factor of approximately 1.5 * (2 <^> 47).