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List:       ms-cryptoapi
Subject:    Re: newbie question: strong encryption with PKZIP + CAPI?
From:       Alan Braggins <armb () NCIPHER ! COM>
Date:       1998-05-29 18:04:27
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> Subject: newbie question: strong encryption with PKZIP + CAPI?
> Date: Thu, 28 May 1998 11:17:03 GMT
> From: Harvey Mace <harveym@FIENDZONE.DEMON.CO.UK>
>
> It appears that strong encryption using CAPI is not legal for
> applications in the UK. Could  anyone tell me how strongly encrypted
> might a file be that is first encrypted with a 40 bit key (maybe using
> CAPI ) , then encrypted again using PKZIP (I believe this employs a
> 96-bit stream cipher). Alternativel;y if anyone knows a better forum
> to place the question could they let me know?

You could try the newsgroup sci.crypt. One important factor will be
whether it's possible to tell when you have found the PKZIP key
without finding the 40 bit key as well - if the PKZIP file has any
standard header information inside the encrypted information, for
example, you only have to do a 40-bit key seach once you have found
the correct PKZIP key, rather than having to do it for each possible
one (136 bit key). If PKZIP, being exportable, really only has 40
bits of keyspace, if you are lucky you have 80 bits, but more likely
you have 41.

> From: Andrejus Chaliapinas <andrejus@MAIL.LBANK.LT>
> In our current payment system (it was developer 3 years ago)
> we are using PKZIP encryption with 10 characters length
> passwords (80bits).
Remember that 10 ASCII characters isn't 80 bits of key entropy.

--
Alan Braggins  mailto:armb@ncipher.com  http://www.ncipher.com/
nCipher Corporation Ltd.  +44 1223 723600  Fax: +44 1223 723601

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