applied cryptography - protocols, algorithms, and source code in c

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Unformatted text preview: ousand keys per second. This rate is far less than the computer’s maximum potential, because we assume it will be doing other things occasionally. Also assume that the typical virus infects 10 million machines. This virus can break a 56-bit key in 83 days and a 64-bit key in 58 years. You might have to bribe the antiviral software makers, but that’s your problem. Any increase in computer speeds or the virus infection rate would, of course, make this attack more efficient. The Chinese Lottery The Chinese Lottery is an eclectic, but possible, suggestion for a massively parallel cryptanalysis machine [1278]. Imagine that a brute-force, million-test-per-second cracking chip was built into every radio and television sold. Each chip is programmed to test a different set of keys automatically upon receiving a plaintext/ciphertext pair over the airwaves. Every time the Chinese government wants to break a key, it broadcasts the data. All the radios and televisions in the country start chugging away. Eventually, the correct key will appear on someone’s display, somewhere in the country. The Chinese government pays a prize to that person; this makes sure that the result is reported promptly and properly, and also helps the sale of radios and televisions with the cracking chips. If every man, woman, and child in China owns a radio or television, then the correct key to a 56-bit algorithm will appear in 61 seconds. If only 1 in 10 Chinese owns a radio or television—closer to reality—the correct key will appear in 10 minutes. The correct key for a 64-bit algorithm will appear in 4.3 hours—43 hours if only 1 in 10 owns a radio or television. Some modifications are required to make this attack practical. First, it would be easier to have each chip try random keys instead of a unique set of keys. This would make the attack about 39 percent slower—not much in light of the numbers we’re working with. Also, the Chinese Communist party would have to mandate that every person listen to or watch a certain show at a certain time, just to make sure that...
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This note was uploaded on 10/18/2010 for the course MATH CS 301 taught by Professor Aliulger during the Fall '10 term at Koç University.

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