Caveat venditor

Tamper-resistant Hardware Security Modules (HSMs) are a core technology used to build assurance in the security of large IT systems protecting and manipulating sensitive data. This paper draws on the authors years of experience working to deploy HSM-based solutions in the financial industry. We argue that as soon as you scratch the surface of the simple ''buy and forget'' model where an HSM is bought to satisfy a compliance requirement, the buyer encounters initial and ongoing challenges when trying to cover all the bases for security. There is now (compared with 10 years ago) a good public literature on HSM vulnerabilities, but even checking resistance against known threats and attack classes becomes very difficult in practice, let alone considering theoretic and new attacks which have not been widely implemented across HSM platforms. Part of the problem is the lack of security details in vendor information, part is lack of awareness of the issues for the buyers. Some older attacks such as the decimalisation table attack have been largely addressed; others such as PIN block translation (and other oracles) have not. This paper argues that the balance of responsibility between buyer and vendor to maintain security awareness has much room for improvement, and that existing certification processes such as FIPS-140 leave huge gaps that need to be covered when building assurance. In the retail sector strong buyer protections exist because the layperson cannot be expected to understand and manage all the relevant risks, but in the financial industry the assumption has been that buyers have the skills to evaluate the products - ''Caveat Emptor''. But maybe it is time to redress this balance with a little ''Caveat Venditor''?