Encrypting data in unprotected memory has gained much interest lately for digital rights protection and security reasons. Counter mode is a well-known encryption scheme. It is a symmetric-key encryption scheme based on any block cipher, e.g. AES. The scheme's encryption algorithm uses a block cipher, a secret key and a counter (or a sequence number) to generate an encryption pad which is XORed with the data stored in memory. Like other memory encryption schemes, this method suffers from the inherent latency of decrypting encrypted data when loading them into the on-chip cache. In this paper, we present a novel technique to hide the latency overhead of decrypting counter mode encrypted memory by predicting the sequence number and pre-computing the encryption pad that we call one-time-pad or OTP. In contrast to the prior techniques of sequence number caching, our mechanism solves the latency issue by using idle decryption engine cycles to speculatively predict and pre-compute OTPs before the corresponding sequence number is loaded. This technique incurs very little area overhead. In addition, a novel adaptive OTP prediction technique is also presented to further improve our regular OTP prediction and precomputation mechanism. This adaptive scheme is not only able to predict encryption pads associated with static and infrequently updated cache lines but also those frequently updated ones as well. Experimental results using SPEC2000 benchmark show an 82% prediction rate. Moreover, we also explore several optimization techniques for improving the prediction accuracy. Two specific techniques, two-level prediction and context-based prediction are presented and evaluated.

Recently, there is a growing interest in the research community to use tamper-resistant processors for software copy protection. Many of these tamper-resistant systems rely on a specially tailored secure processor to prevent, 1) illegal software duplication, 2) unauthorized software modification, and 3)unauthorized software reverse engineering. The published techniques primarily focused on feasibility demonstration and design details rather than analyzing security risks and potential attacks from an adversary's perspective. The uniqueness of software copy protection may lead to some potential attacks on such a secure environment that have been largely ignored or insufficiently addressed in the literature. One should not take security for granted just because it is implemented on a tamper-resistant secure processor. Detailed analysis on some proposed ideas reveal potential vulnerability and attacks. Some of the attacks are known to the security community, nevertheless, their implications to software copy protection are not well understood and discussed. This paper presents these cases for designers to improve their systems and circumvent the potential security pitfalls and for users of such systems to be aware of the potential risks

The blooming e-commerce is demanding better methods to protect online users' privacy, especially the credit card information that is widely used in online shopping. Holding all these data in a central database of the Web sites would attract hackers' attacks, impose unnecessary liability on the merchant Web sites, and raise the customers' privacy concerns. We introduce and discuss in detail the secure distributed storage of sensitive information using HTTP cookie encryption. We are able to employ One-Time Pads to encrypt the cookies, because encryption and decryption are both done by the server, which is an interesting characteristic overlooked by the existing systems. We implemented this protocol and showed that it is simple, fast and easy to program with.