Cryptosystem designers frequently assume that secrets will be manipulated in closed, reliable computing environments. Unfortunately, actual computers and microchips leak information about the operations they process. This paper examines speciaec methods for analyzing power consumption measurements to aend secret keys from tamper resistant devices. We also discuss approaches for building cryptosystems that can operate securely in existing hardware that leaks information.

The power consumed by a circuit varies according to the activity of its individual transistors and other components. As a result, measurements of the power used by actual computers or microchips contain information about the operations being performed and the data being processed. Cryptographic designs have traditionally assumed that secrets are manipulated in environments that expose no information beyond the specified inputs and outputs. This paper examines how information leaked through power consumption and other side channels can be analyzed to extract secret keys from a wide range of devices. The attacks are practical, non-invasive, and highly effective-even against complex and noisy systems where cryptographic computations account for only a small fraction of the overall power consumption. We also introduce approaches for preventing DPA attacks and for building cryptosystems that remain secure even when implemented in hardware that leaks.

The RSA trapdoor proposed in Ross Anderson's recent letter can be broken. A recent letter by Ross Anderson 1] proposes a \trapdoor" in the RSA public-key cryptosystem 5] whereby a hardware device generates RSA primes

In this paper we propose an innovative method to test integrated circuits based on the use of Differential Power Analysis. We will show that this technique, classically used to perform attacks on cryptographic devices, is very effective in observing single stuck-at faults. Based on the observation of the current consumed by the circuit during net transitions, it does not require observing primary outputs of the circuit and allows the test of hard-to-observe faults. Conversely to Iddq, this technique is not sensible to process variation.

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