Unformatted text preview: atement. To access the contents, click the chapter and section titles. Applied Cryptography, Second Edition: Protocols, Algorthms, and Source Code in C (cloth)
Brief Full Advanced Search Search Tips (Publisher: John Wiley & Sons, Inc.) Author(s): Bruce Schneier ISBN: 0471128457 Publication Date: 01/01/96 Search this book:
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The greatest difficulty in getting millions of computers to work on a brute-force attack is convincing millions of computer owners to participate. You could ask politely, but that’s time-consuming and they might say no. You could try breaking into their machines, but that’s even more time-consuming and you might get arrested. You could also use a computer virus to spread the cracking program more efficiently over as many computers as possible. This is a particularly insidious idea, first presented in . The attacker writes and lets loose a computer virus. This virus doesn’t reformat the hard drive or delete files; it works on a brute-force cryptanalysis problem whenever the computer is idle. Various studies have shown that microcomputers are idle between 70 percent and 90 percent of the time, so the virus shouldn’t have any trouble finding time to work on its task. If it is otherwise benign, it might even escape notice while it does its work. Eventually, one machine will stumble on the correct key. At this point there are two ways of proceeding. First, the virus could spawn a different virus. It wouldn’t do anything but reproduce and delete any copies of the cracking virus it finds but would contain the information about the correct key. This new virus would simply propagate through the computer world until it lands on the computer of the person who wrote the original virus. A second, sneakier approach would be for the virus to display this message on the screen: There is a serious bug in this computer. Please call 1-800-123-4567 and read the following 64-bit number to the operator: xxxx xxxx xxxx xxxx There is a $100 reward for the first person to report this bug. How efficient is this attack? Assume the typical infected computer tries a th...
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