User:Sandy Harris

 Where Sandy lives it is approximately: 01:04

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 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.

Citizendium articles where I was the main 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]
•  Brute force attack: An attempt to break a cipher by trying all possible keys; long enough keys make this impractical. ^[e]
•  Cypherpunk: People interested in cryptography as a tool for privacy, anonymity and social change. ^[e]
•  FreeSWAN: A Linux implementation of the IPsec protocols, intended to make wholesale monitoring of the Internet impossible. ^[e]

including many on 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]
•  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]

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]

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.