Unclonable Identifier

Full Title or Meme

An Unclonable Identity is based on some physical measurement that cannot be reproduced else where.

Context

• Security Tokens have existed since prehistory using some physical stamp with wax or ink to create an impression that could not be duplicated with then existing technology.
• The most common private Identifier on the web today is a Private Key that is created and kept secret by the owner of the key.
• Most naturally occurring materials will have some random characterizes which are randomly disbursed throughout the material.

Problem

• To function as an Identifier, the material object needs to have some element of randomness that can be read out of the object producing some repeatable string.
• It is still necessary to ensure that it is the material object that is being read, and not just a replay of a prior read out.

Solutions

Lots of attempts have been made to create a physical unclonable function (PUF), some of which are listed here.

1. Optical - puts scattered defects in an optical media that have been called a "Speckle Pattern".
2. Coating - puts a pattern on the top of, for example, a silicon chip that can be read by the chip, but is covered by a material which is opaque and part of the pattern's read out capability.
3. Delay - based on delays in materials, like silicon, that are able to be reliably read out.
4. SRAM - naturally comes with defects that can be read out. Many patents and products are now available using this to hide a crypto key or create an RFID chip.
5. Quantum - which are completely unclonable, but hard to maintain over any period of time longer than a second. Application have been found in establishing secure communications channels.