A transparent token the size of a postage stamp and costing just a penny to make can be used to generate an immensely powerful cryptographic key.
Current cryptographic systems use mathematics to generate the numerical "keys" that lock up the protected data. These are produced using "one-way functions", formulas that take simple secret data and generate long keys. The trick is that it is extremely hard to reverse the process and work back to the secret data when given only the key.
Now researchers at MIT Media Lab"s Center for Bits and Atoms have shown it is possible to use a physical object instead of a mathematical function to generate keys. The trick here is that the object is currently impossible to duplicate.
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.