RE: [vhdl-200x] Protect tool - Key block clarification

An initial vector can easily be associated with a key-owner/key-name;
rather than having a key associated with a key-owner/key-name, it would
be a key and initial vector pair. Since key exchange is implementation
defined, exchanging a key and initial vector pair doesn't contradict the
existing standard.

If a tag for IV were added, it would have to be treated the same way
keys are, or the default would be implementation defined. When using a
'default' key for encryption, the encrypting tool specifies the
key-owner/key-name for its default key so other tools know what key to
use.

-----------------------
Michael Smith
R&D Engineer, SaberHDL
Synopsys Inc.
mtsmith@synopsys.com
-----------------------

-----Original Message-----
From: Jarek Kaczynski [mailto:jarek@aldec.com] 
Sent: Monday, July 16, 2007 5:40 PM
To: Peter Ashenden; Michael Smith; vhdl-200x@eda.org
Cc: vhdl-lrm@lists.accellera.org
Subject: RE: [vhdl-200x] Protect tool - Key block clarification

The only working implementation I know (Synplicity's Open IP Encryption)
uses quite unfortunate solution: fixed IV (both encrypting and
decrypting tool use assumed value). If IP vendor for some reason decides
to use the same encryption key for subsequent encryption sessions, it
makes code-breaking task much easier if the code-breaker has access to
more than one encrypted file. The problem is less painful if random key
is used for each encryption session.
For the sake of backwards compatibility, I would suggest to use 'assume
default if explicit data not present' rule:
-- create new tag for IV, so that symmetric key and IV can be specified
clearly
-- if either key or IV is missing in the decryption envelope, tool
default is used
Anybody knows how Cadence (the originator of the donation) does it?

Thank you,

Jerry Kaczynski 


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