[Tutor] Iterate over letters in a word

Danny Yoo dyoo at hkn.eecs.berkeley.edu
Tue Mar 14 22:12:39 CET 2006

> As a side note, remember that that xor-ing a key with a message is
> trivial to break (it's just a variation on the Vigenere cipher first
> published in 1568). So don't use if for any real applications.

Hi Matthew,

Counterpoint: think of "one-time pads".


XOR itself is just a technique --- it's just a binary operation between
two bit patterns --- but the use of one-time pads provides unbreakable
encryption.  As long as the xor-ing key is protected, and as long as the
encrypting key pattern is as long as the message, it's theoretically

If we reuse the same encrypting bit-pattern over and over, or make the
XORing key less than random, then all bets are off, of course.  *grin*

There are different encryption schemes that, at its heart, use XOR.  But
XOR itself is not inherently insecure: it's our use of it that determines
the quality of the result.

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