International Association for Cryptologic Research

International Association
for Cryptologic Research


Bruno Crispo


Towards a Theory of White-Box Security
Program hardening for secure execution in remote untrusted environment is an important yet elusive goal of security, with numerous attempts and efforts of the research community to produce secure solutions. Obfuscation is the prevailing practical technique employed to tackle this issue. Unfortunately, no provably secure obfuscation techniques currently exist. Moreover, Barak et al., showed that not all programs can be obfuscated. We present a rigorous approach to {\em program hardening}, based on a new white box primitive, the {\em White Box Remote Program Execution (WBRPE)}, whose security specifications include confidentiality and integrity of both the local and the remote hosts. We then show how the {\em WBRPE} can be used to address the needs of a wide range of applications, e.g. grid computing and mobile agents. Next, we construct a specific program and show that if there exists a secure {\em WBRPE} for that program, then there is a secure {\em WBRPE} for {\em any} program, reducing its security to the underlying {\em WBRPE} primitive. This reduction among two white box primitives introduces new techniques that employ program manipulation.
Reverse SSL: Improved Server Performance and DoS Resistance for SSL Handshakes
Common occurrence of server overload and the threat of denial-of-service (DoS) attacks makes highly desirable to improve the performance and DoS resistance of SSL handshakes. In this paper, we tackle these two related problems by proposing reverse SSL, an extension in which the server is relieved from the heavy public key decryption operation and authenticated by means of a digital signature instead. On the server side, reverse SSL employs online/offline signatures to minimize the online computation required to generate the signature and on the client side, RSA key generation computation can be used as a client puzzle when clients do not have a public key certificate. The preliminary performance results show that reverse SSL is a promising technique for improving the performance and DoS resistance of SSL servers.