[Cryptography] What is the difference between a code and a cipher?

Bill Frantz frantz at pwpconsult.com
Thu Sep 4 19:14:55 EDT 2014


On 9/4/14 at 8:16 PM, zenadsl6186 at zen.co.uk (Peter Fairbrother) wrote:

>I don't know whether there is a definitive answer, but opinions are sought.

It seems to me that "code" is short for "encoding". In ham radio 
we are not permitted to try to obscure the meaning of 
transmissions, but we can and do use a large number of codes. We 
have lots of examples of codes which are not intended to provide 
secrecy. Examples from ham radio are Morse code, ASCII code, 
Baudot code, and Varicode. Other codes attempt to reduce the 
length of information. The ham radio "Q" codes perform this role 
and have the added advantage of allowing people who do not speak 
a common language to communicate. For example, QTH? means, "What 
it your location?"

Cyphers on the other hand are always meant to obscure meaning. 
They do not shorten messages.

One story from David Kahn's "Code Breakers" serves to illustrate 
this point. In the time leading up to World War II, the US 
government forbid the use of codes on international telegraph 
lines. Many companies objected strongly. Their issue wasn't 
secrecy. It was an increase of 5 to 10 in the cost of the 
telegrams. The solution was the "Uniform Commercial Code", which 
had the data compression function without the secrecy.

Cheers - Bill

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