Non-ATT 'crypt(3)'

[Bill.Stewart.4K435.x0705]

In article <125 at suneast.uucp> geoff at suneast.uucp (Geoff Arnold) writes:
>Alex Osadzinski, Unix Europe Ltd, London, England
>writes:
>> ... Further, any competent programmer
>> can reproduce the crypt(3) code in an afternoon from a functional description.
>
>Oh really? The problem is, the only functional description other than the
>code is the 'crypt(3)' man page, which vaguely says that the 'salt' is
>"used to  perturb  the DES algorithm in one of 4096 different ways". Can you
>deduce the algorithm without looking at the code?

The important thing is to get the interface right; for normal
applications it's unnecessary to pass crypt(3)'ed passwords between
systems; if you depend on that then propagate your own crypt routine as
well as your application.  The salt business has two main purposes:
	- make it impossible to use DES hardware to decrypt
		(software is much slower, and if the speculated-about
		NSA trapdoor exists, this may make it fail.)
	- produce different cyphertexts for identical plaintext
		encrypted with identical keys - this makes cryptanalysis
		much more difficult, and makes it hard to tell that
		you're using the same passwords on N different machines.
As long as you've got the interfaces correct, the internals don't
really matter much.
-- 
# Bill Stewart, AT&T Bell Labs 2G-202, Holmdel NJ 1-201-949-0705 ihnp4!ho95c!wcs