Yes Jimmy, you are correct.  MD5 is a one-way hash.  Its used for 
getting a unique fingerprint of some data (like files / passwords 
etc) so that it can be compared with another MD5 hash.

Thats the point of a hashing algorithm like MD5 and SHA1 - you 
should never need to decrypt the data.

Refer to how Digital signatures and PKI works - they use MD5 

The next question - A bigger keylength means stronger encryption - 
but it also means more CPU cycles.

A bigger blocksize means that bigger chunks of data are encrypted 
at a time.

Its always a balance that needs to be found over here - you cant 
use a keylength that is 2048 bits - it will give u the strongest 
encryption, but it will also take a lot of time.


On Wed, 22 May 2002 Jimmy Lantz wrote :
>Thanx for the suggestions!
>Someone mentioned that I could use MD5 and then encrypt the 
>how would I ever decrypt that? Is'nt MD5 a 1-way thing only?
>Another question?
>Should I go for bigger keylength or bigger blocksize or both? 
>What makes for the best encryption?
>/ Jim
>(and before someone suggest that I read the book Applied 
>cryptography it's already orderd and on it's way :-) )
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