Focus: Multiparadigm Programming Focus: Multiparadigm Programming Focus: Multiparadigm Programming

A COMPUTER SYSTEM’S security can be compromised in many ways— a denial-of-service attack can make a server inoperable, a worm can destroy a user’s private data, or an eavesdropper can reap fi nancial rewards by inserting himself in the communication link between a customer and her bank through a man-in-the-middle (MITM) attack. What all these scenarios have in common is that the adversary is an untrusted entity that attacks a system from the outside—we assume that the computers under attack are operated by benign and trusted users. But if we remove this assumption, if we allow anyone operating a computer system— from system administrators down to ordinary users—to compromise that system’s security, we fi nd ourselves in a scenario that has received comparatively little attention. Attacks by a trusted user on a computer system, called a man-at-theend (MATE) scenario, can take many forms. In a tampering attack, an adversary violates the integrity of a piece of software under his control, perhaps by modifying it in ways the software vendor didn’t intend. In a malicious reverse engineering attack, he violates the vendor’s confi dentiality rights by extracting intellectual property from the software, such as algorithms, designs, or implementations. Finally, in a cloning attack, he violates copyright laws by making and distributing illegal copies of the software. Methods for protecting against MATE attacks are variously known as anti-tamper techniques, digital asset protection, or, more commonly, software protection.1 To protect against tampering attacks, tamper-proofi ng techniques look for modifi cations to a program, and when they fi nd them, take offensive or defensive measures. For example, a tamper-proof program can reSoftware Protection