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Biometric word list

A biometric word list is a list of words that can be used to authentically and reliably communicate numeric information by voice. The words in the list correspond to one of each of the 256 unique byte values, and are carefully chosen for their phonetic distinctness. The properties of the human voice serve as the authentication mechanism. The idea was originated by Phil Zimmermann, the inventor of PGP, and Patrick Juola, a computational linguist.

The first (and only?) biometric word list is one developed by Zimmermann and Juola, with the assistance of Zhahai Stewart and Grady Ward. It was developed to permit the verbal authentication of Diffie-Hellman key exchange, and of cryptographic key fingerprints. The information conveyed using a biometric word list can also be conveyed by simply reading decimal or hexadecimal numbers. However, some numbers sound similar to each other ("five" and "nine"; "B" and "D"; etc.) and can lead to errors in "transmission", so the conversion to words is used. It is similar to the use of the military alphabet for the communication of letters.

The Zimmermann/Juola list is actually composed of two parallel lists, one of two-syllable words, the other of three-syllable words. To compose the verbal equivalent of a numeric value, the two lists are used in an alternating manner; the first byte is represented by the appropriate word in the two-syllable list; the next byte by the appropriate word in the three-syllable list; etc. This serves as an error detection mechanism, to address the tendency of people to transpose consecutive words, duplicate words, and omit words when reading aloud lists of random words.

For example, some words from the parallel lists are as follows:

Byte Corresponding words
(hex value) Two-Syllable Three-Syllable
20 bison butterfat
29 breakup certify
6B glitter Hamilton
FE woodlark yesteryear
38 classic consulting
0D ancient asteroid
D2 standard sensation

Thus, the randomly chosen sixteen-digit decimal number 9052743058066898, equivalent to the fourteen-digit hexadecimal number 20 29 6B FE 38 0D D2 (with spaces added for clarity of demonstration) is represented by the seven-word sequence, "bison certify glitter yesteryear classic asteroid standard", as shown by the boldfaced words in the table.

External link

PGP User's Guide (pdf 2.13MB)