Re: IDEA encryption

["Mark M." <markm@omni.voicenet.com>]

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On Tue, 12 Dec 1995, Ben Holiday wrote:

> 
> The copy of the source for idea (unix) that I have specify's a user key 
> length of 8 bytes, but allows this to be increased to something larger. 
> Will increasing the user keylength improve the overall security? 
> 
IDEA uses 128-bit keys.  The program must do some XORing with the user key
to expand it to 16 bytes.  Therefore, I would guess that it would be more
secure to use a longer key.

> Also, is it worth hashing the user key first, then using the hashed key 
> as the key for encryption and decryption? Or am I wasting my time? 
> 
It probably isn't going to help with security at all if you plan to use a
hexadecimal representation of the hash as is the common output of hashing
programs.  The best key would be one that uses random letters, numbers, and
symbols.

> Last thing -- how secure is unix "rm"?  If something is rm'd, is it 
> really really gone? 
> 

Not very secure.  I have heard that there is a Linux undelete and there might
be a similar program for other Unices.  If the hard drive is examined using
special hardware, data will be recoverable.  The data should be overwritten
at least five times, maybe more depending on the level of security you want,
before being deleted.


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finger markm@voicenet.com for Public Key http://www.voicenet.com/~markm/
Key-ID: 0xF9B22BA5 Fingerprint: bd24d08e3cbb53472054fa56002258d5
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w--- O- M- V-- PS+++>$ PE-(++) Y++ PGP+(++) t-@ 5? X++ R-- tv+
b+++ DI+ D++ G+++ e! h* r! y?
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