User:Sandy Harris

 Where Sandy lives it is approximately: 03:00

I'm a baby-boomer Canadian currently teaching English and IT subjects in China. My academic qualifications are a BA in Psychology and a Certificate in Teaching English as a Second Language, both from Carleton U in Ottawa. I also did some work toward an M Phil in computational linguistics at U of Birmingham, UK, but did not complete that degree.

I am quite active on Wikitravel, where I'm an admin, and sometimes contribute to other wikis. See my Wikitravel user page: [1].

I've spent two substantial chunks of my career as a teacher — 1978-83 and 2002-date — mainly because that is a good way to support travel. At other times I've worked in computing, mostly as a technical writer but a bit of everything else too.

I'm interested in computer security and cryptography. I think my latest papers ([2], [3]) on combining stream ciphers and block ciphers, are fairly interesting.

My Erdos number is five, via Carlisle Adams, Michael Weiner and Ron Rivest.

I wrote most of the documentation for the FreeS/WAN project, a Linux implementation of the IPsec encryption protocols. I have permission to re-use that text here User_talk:Sandy_Harris/Permission.

Articles

For quite a few Citizendium articles, I was the main or only writer:

•  Block cipher: A symmetric cipher that operates on fixed-size blocks of plaintext, giving a block of ciphertext for each ^[e]
•  Stream cipher: A cipher that encrypts data by mixing it with the output of a pseudorandom number generator controlled by a key; to decrypt, run the same generator with the same key to get the same pseudorandom data, then reverse the mixing step. ^[e]
•  Kerckhoffs' Principle: The principle, formulated by Auguste Kerckhoffs, that security in a cipher should not depend on keeping the details of the cipher secret; it should depend only on keeping the key secret. ^[e]
• Cypherpunk: Add brief definition or description
•  FreeSWAN: A Linux implementation of the IPsec protocols, intended to make wholesale monitoring of the Internet impossible. ^[e]
•  Hash (cryptography): An algorithm that produces a fixed-size digest from an input of essentially arbitrary size. ^[e]
•  AES competition: A competition run by the US National Institute of Standards and Technology to chose a block cipher to become the Advanced Encryption Standard. ^[e]

More specific articles

Articles on specific attacks:

•  Active attack: An attack on a communications system in which the attacker creates, alters, replaces, re-routes or blocks messages; this contrasts with a passive attack in which he only reads them. ^[e]
•  Passive attack: An attack on a communications system in which the attacker reads messages he is not supposed to but does not alter them. ^[e]
•  Brute force attack: An attempt to break a cipher by trying all possible keys; long enough keys make this impractical. ^[e]
•  Algebraic attack: Attacking a cipher by writing equations that describe its operation, then solving for the key. ^[e]
•  Code book attack: Attacking a block cipher by creating a code book, collecting plaintext/ciphertext pairs. ^[e]
•  Birthday attack: An attack on a cryptographic system that works by finding two identical outputs from the system. ^[e]
•  Meet-in-the-middle attack: An attack on a block cipher in which the attacker can calculate possible values of the same intermediate variable (the middle) in two independent ways, starting either from the input of the cipher (plaintext) or from the output ( ciphertext); he calculates some possible values each way and compares the results. ^[e]
•  Man-in-the-middle attack: An attack on a communications system in which the attacker deceives the communicating parties so they both talk to him while believing they are talking to each other. ^[e]

On specific ciphers:

•  CAST (cipher): A general procedure for constructing a family of block ciphers. ^[e]
•  Serpent (cipher): A block cipher which was a finalist in the Advanced Encryption Standard (AES) contest, designed by Ross Anderson, Eli Biham, and Lars Knudsen. ^[e]
•  Blowfish (cipher): A block cipher, designed in 1993 by Bruce Schneier and included in a large number of cipher suites and encryption products. ^[e]
•  MARS (cipher): A block cipher that was IBM's submission to the Advanced Encryption Standard process. ^[e]
•  Twofish (cipher): A bock cipher from Schneier and others that was a finalist in the AES competition. ^[e]

Others

Others I have contributed heavily to:

•  Cryptography: A field at the intersection of mathematics and computer science that is concerned with the security of information, typically the confidentiality, integrity and authenticity of some message. ^[e]
•  Cryptanalysis: The sub-field of cryptology which deals with breaking into existing codes and ciphers. ^[e]
•  IPsec: Internet Protocl security is a set of protocols for providing encryption and/or authentication services for Internet packets. ^[e]