No subject

"PDFs standard encryption methods use the MD5 message-digest algorithm
(de-scribed in Internet RFC 1321, The MD5 Message-Digest Algorithm; see
the Bibli-ography) and a proprietary encryption algorithm known as RC4.
RC4 is a symmetric stream cipher (the same algorithm is used for both
encryption and decryption), and the algorithm does not change the length
of the data.

Note: RC4 is a copyrighted, proprietary algorithm of RSA Security, Inc.
Adobe Systems has licensed this algorithm for use in its Acrobat products.
Independent software vendors may be required to license RC4 in order to
develop software that encrypts or decrypts PDF documents. For further
information, visit the RSA Web site at <http://www.rsasecurity.com> or
send e-mail to <products at rsasecurity.com>."

> Adobe never seems to
> have had any trouble exporting their Acrobat viewer software.  I know
> there is a version of xpdf that Debian's non-us (xpdf-i) but I can't see
> how the crypto could possible offer any protection.  

More from the specs:

"In particular, PDFs stan-dard encryption handler limits the key to 5
bytes (40 bits) in length, in accor-dance with U.S. cryptographic export
requirements in effect at the time of initial publication of the PDF 1.3
specification."


-- 
Andrew Francis
locust at iinet.net.au