| Biometric Word List |
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This list was designed in 1995 by Patrick Juola , a computational linguist, and Philip Zimmermann , creator of PGP . The words were carefully chosen for their Phonetic distinctiveness, using Genetic Algorithms to select lists of words that had optimum separations in Phoneme space. Grady Ward 's Moby Pronunciator list was used as raw material to search for words. The Zimmermann/Juola list was originally designed to be used in PGPfone , a secure VoIP application, to allow the two parties to verbally compare a short authentication string to detect a Man-in-the-middle Attack (MiTM). It was called a Biometric word list because the authentication depended on the two human users recognizing each other's distinct voices as they read and compared the words over the voice channel, binding the identity of the speaker with the words, which helped protect against the MiTM attack. The list can be used in many other situations where a biometric binding of identity is not needed, so calling it a biometric word list may be imprecise. Later, it was used in PGP to compare and verify PGP Public Key Fingerprints over a voice channel. This is known in PGP applications as the "biometric" representation. When it was applied to PGP, the list of words was further refined, with contributions by Jon Callas. More recently, it has been used in Zfone and the ZRTP protocol, the successor to PGPfone. Each list contains 256 ; the even list has words of two syllables, the odd list has three. Using a two-list scheme was suggested by Zhahai Stewart. WORD LISTS EXAMPLES Each byte in a bytestring is encoded as a single word. For example, the least significant byte (i.e. byte 0) is considered "even" and is encoded using the PGP Even Word table. The next most significant byte (i.e. byte 1) is considered "odd" and is encoded using the PGP Odd Word table. This process repeats until all bytes are encoded. Thus, "E582" produces "topmost Istanbul", whereas "82E5" produces "miser travesty". A PGP public key fingerprint that displayed in hexadecimal as : E582 94F2 E9A2 2748 6E8B: 061B 31CC 528F D7FA 8919would display in PGP Words (the "biometric" fingerprint) as : topmost Istanbul Pluto vagabond: treadmill Pacific brackish dictator: goldfish Medusa afflict bravado: chatter revolver Dupont midsummer: stopwatch whimsical nightbird bottomlessThe order of bytes in a bytestring is a topic discussed at length in computer science and engineering, and is beyond the scope of this article. This is often referred to as Endianness . REFERENCES Patrick Juola & Philip Zimmermann. [http://www.mathcs.duq.edu/~juola/papers.d/icslp96.pdf "Whole-Word Phonetic Distances and the PGPfone Alphabet" (1996)]. Proceedings of the International Conference of Spoken Language Processing (ICSLP-96) COPYRIGHT This material is copyrighted under a copyright owned by PGP Corporation. They have now granted a license under the GNU Free Documentation License. (per Jon Callas, CTO, CSO PGP Corporation, 4-Jan-2007) EXTERNAL LINKS |
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