Ransomware

[Arshad Noor]

----- Original Message -----
From: "Jerry Leichter" <leichter_jerrold at emc.com>
To: "Dave Korn" <dave.korn at artimi.com>
Cc: "Email List - Cryptography" <cryptography at metzdowd.com>
Sent: Wednesday, June 11, 2008 12:04:21 PM (GMT-0800) America/Los_Angeles
Subject: RE: Ransomware

|   Why are we wasting time even considering trying to break the public key?
| 
|   If this thing generates only a single "session" key (rather, a host key)
| per machine, then why is it not trivial to break?  The actual encryption
| algorithm used is RC4, so if they're using a constant key without a unique
| IV per file, it should be trivial to reconstruct the keystream by XORing any
| two large files that have been encrypted by the virus on the same machine.

This is the first time I've seen any mention of RC4.  *If* they are
using RC4, and *if* they are using it incorrectly - then yes, this
would certainly work.  

	It is interesting that Kaspersky Labs has not published the
        code to the disassembled virus.  They want the whole world to
        stop what they're doing to factor a 1,024-bit key, but they
        are unwilling to publish details of the virus' mechanics.  
        This is out of character for someone who is truly interested
        in solving the problem for the long-term.

        While their forum has the detail of the RSA key, they've 
        categorically indicated that they will not explain the 
        cryptography publicly, except to experts over e-mail.  I 
        presume this is how David learned of the RC4 algorithm?

        Arshad Noor
        StrongAuth, Inc.

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