COMMAND
MS Access 'known database attack'
SYSTEMS AFFECTED
Win running MS Access 2.0 (others?)
PROBLEM
Mark Rosen has examined the encryption on MS Access (v 2.0) and
found that it was really easy to break without ever having to
determine the key. It is RC4 based. During examination of it,
he found it behaved as a stream cipher where the stream was
XORed with the database. MS Access databases grow in 2K
increments, so it makes since that everything is done the way
described below.
However, encrypting with MS Access has a major flaw: It does not
ask you for a password! You might expect that, like almost every
other thing with encryption, you would be prompted for a password.
In effect the same key is used for encryption and decryption.
The method to break:
- Create a known database which is at least as large as the
database you are trying to break.
- Encrypt it.
- Find the XOR between the known database and its encryption.
This is the key stream.
- XOR the key stream against the target database you are
trying to break.
So there is no need for a brute force attack. MS can use a
900,000+ bit key and it won't matter.
SOLUTION
Microsoft Access versions 1.0, 1.1, 2.0, 7.0 have same encryption
so there is potentional danger. Anyway, nothing you can do here
more. Leave it MS.