Known-plaintext attack on Encrypted Magic Folders

[staym at accessdata.com]

Encrypted Magic Folders is a very popular shareware title from PC-Magic.
Magic Folders, its predecessor, was designed to intercept file IO
requests in Windows and return "File Not Found" if the file was in a
marked folder. It does this reasonably well, although booting into DOS
exposes all the files. To solve this problem, PC-Magic chose to roll
their own encryption. Reading the documentation about EMF's encryption
is frightening: as one cypherpunk put it, "Smells like snake oil, looks
like snake oil, it even has bits of snake scales in it." Here we show
that EMF is susceptible to a known-plaintext attack that needs as few as
768 bytes. 

http://www.accessdata.com/emf_cryptanalysis.html
-- 
Mike Stay
Programmer / Crypto guy
AccessData Corp.
staym at accessdata.com