"Bad Timing: A loophole is found in a popular encryption scheme,"by Charles Seife. Scientific American, March 1996, page 36.
Recently cryptography consultant Paul C. Kocher announced a way to get aroundpublic key encryption schemes. Rather than attacking the encryption directly,he developed a way to examine how long it takes computers to decrypt amessage. Repeated observations of the timing permit an analysis of what wentinto the decryption and finally the discovery of the encryption key. Thisscheme can be foiled by having computers take extra time in decrypting themessage. However, this work shows that encryption schemes will always bevulnerable to new attacks.