Re: [oic] encryption of signature files

[robert_weir@us.ibm.com]

I'm not certain what Dennis is referring to, but it might be the 
known-text attack on ZIP files that has been known for 15 years or so. 
Essentially, the table of contents for the ZIP file readable by anyone, so 
if you can look at the names of the files in the ZIP and correctly guess a 
portion of the plain text in one of those files, you can reduce the cost 
of a brute force attack to determine the encryption key.  The more bits 
you can guess in the plain text, the easier it will be to recover the key. 
 

-Rob


Hanssens Bart <Bart.Hanssens@fedict.be> wrote on 12/11/2009 01:06:20 PM:


> 
> > I have a pent-up pending analysis and blog post on the ODF 1.x package
> > encryption scheme's vulnerability to known-plaintext attacks.  Thefact 
that
> > the digital signature files cannot be encrypted is also something that
> > should raise eyebrows in document security circles.
> 
> Hmz, probably I'm missing something here, but I haven't read that one 
cannot
> encrypt the signature files (or other files in META-INF, except the 
> manifest.xml)
> 
> As far as I know, one cannot encrypt the manifest (otherwise it'll be a 
tad
> difficult to get to the encryption/decryption parameters), nor the 
mimetype
> stream...
> 
> Part 3 mentions that, for encrypted documents, Thumbnails/thumbnail.png
> may be a dummy one (but I haven't seen a statement that one isn't allow 
to
> simply encrypt that one as well, although that might cause some trouble 
for
> environments trying to show the preview, so probably not a good idea)
>