RACF password encryption is explained here:

http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/ichza290/3.3.1

It uses Triple DES where the password is a key to encrypt the userid,
which encrypted value is then stored in the DB. So two different users
with the same password would have two different encrypted values. It
also states it is a "one way" encryption. There is no way to "back out".
To crack a password would require having the unencrypted RACF id, the
encrypted stored value, and the exact algorithm. Now, I'm not a
cryptographer, but I don't think you can use that information to
recreate a valid password easily. So you're more likely to try a brute
force dictionary attack. Again, using an NSA quality supercomputer, I
have no idea how long this would take. I think I'd just play the lotto
and win sooner. But that is my ignorance speaking. 

On Sun, 2010-11-28 at 19:15 -0600, Paul Gilmartin wrote:
> On Sun, 28 Nov 2010 15:56:36 -0600, Russell Witt wrote:
> 
> >Easy to say "do not share your RACF db"; harder in reality. Most sites
> >believe they are safe because their RACF db is security protected and the
> >dasd is not shared. And then completely forget that backups (to physical or
> >virtual tape) contain the exact same information. And quite often the DSN
> >used for the backup tapes is some type of dasd-manager HLQ, since it was
> >most likely a full-volume backup that happen'ed to contain the RACF db. And
> >even if the HLQ for the full-volume backups is read-protected; it is still
> >far easier to hack a tape dataset. Often, tape libraries (physical and
> >virtual) are shared with less-secure test machines and quite often even with
> >non z/OS systems. Granted, you will need the physical layout of the RACF db;
> >but not the entire layout. Just enough to identify where the passphrases are
> >maintained.
> >
> Aren't the passwords encrypted?  But how strong is the encryption?
> 
> It would be peculiarly pointless to store fewer bits of the encrypted
> password than are used in the encrypting key.
> 
> -- gil
> 
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