Re^2: Encryption in Perl?

AFAICT, this is the "encryption" loop from My::Crypt:

for ($j = 0; $j < length($a); $j++) {
    substr($a, $j, 1) += substr($b, $i, 1);
    substr($a, $j, 1) = 0 if substr($a, $j, 1) == 2;
    $i = 0 if ++$i > length($priv);
}
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In other words, it's a completely naive implementation of simple XOR. Avoid at all costs.

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Re^3: Encryption in Perl? by CombatSquirrel (Hermit) on Jul 19, 2004 at 19:09 UTC
On the other hand the one-time pad, which is a Vignère ('simple XOR') variant with key length equal to or greater than the plain text length, is the only possible encryption algorithm with perfect secrecy, as was proven by Shannon. Most other applications of the Vignère cipher (I just hesitate to say 'all') are quite easy to break, which everyone who ever attempted to break it will have found out. The point is that "encryption/decryption" is not enough information to decide which algorithm to use. Even ROT13 can be permissible when the issue is not reasonable secrecy but the fear of revealing data to someone who does not want to know it. And here we are. My advice to the OP: Unless you only meant to find modules and already read a couple of books on cryptology and cryptanalysis, better do it now. It is not neccessary, but in my eyes it'll help you understand your problem better. References: Gaines, Schneier, etc., pp. Hope this helped. CombatSquirrel. Entropy is the tendency of everything going to hell.	[reply]

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Re^3: Encryption in Perl?
by CombatSquirrel (Hermit) on Jul 19, 2004 at 19:09 UTC

CombatSquirrel

Entropy is the tendency of everything going to hell.

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