newscientist: Transparent token is cryptographic key
New Scientist reports MIT researchers have developed a method of creating physical objects that cannot be duplicated. The article talks about cryptographic applications; however, a lengthy thread on the Cryptography mailing list suggests it has limited use as a cryptographic tool - its real use is as an authentication tool that doesn't require cryptography at all.
The team created tokens containing hundreds of glass beads, each a few hundred micrometres in diameter, set in a block of epoxy one centimetre square and 2.5 mm thick. These are "read" by shining a laser beam of a particular wavelength through the token. The beam generates a speckle inteference pattern, which is projected onto a two-dimensional grid and then converted into a key 2400 bits long. Changing the position of one of the randomly set beads even by less than a micrometre, changes about half the bits in the key. This sensitivity means that the token could not be duplicated using any manufacturing technology in existence or planned. Furthermore, changing the angle at which the laser passes through the token can generate new unique codes. One future use of the tokens could see them being embedded into credit cards. One of the MIT team, Neil Gershenfeld, says the unique nature of the tokens could also make them useful for other security applications. (see www.newscientist.com)