Re: PasswordSafe format v3 - discussion

Hi,

On Thu, 01 Dec 2005 15:25:20 -0500, Rony Shapiro <[email protected]> wrote:
>
> Dave Collins:
>> I believe we need a MAC to autheticate the data. I propose HMAC-SHA256
>
> This is, in principle, a Good Idea. It can certainly protect a database
> against cut&paste attacks. The question is, how vulnerable is the  
> database to such attacks in practice?
> (2) there should be a special "End of Records" block in the file before
> the MAC, to assist parsing.
>

The end of records block is sufficient to detect truncated files. The
MAC is only needed if an attacker were able to break the encryption, on
the assumption that the attacker might be able to defeat Twofish but
unable to defeat the MAC. But if there are attacks on Twofish, we're
probably screwed anyway.

>
>> I would not use a file extension to make any decisions on content!
>
> That was not my intent: A different suffix would merely be a useful
> convention for managing versions. The logic DK outlined can be used in  
> any case.
>

IMHO, file extensions are overrated.

What I would like to see instead/in addition is a "magic" tag at the
beginning of the file, i.e. a well-defined string or value that uniquely
identifies the password safe format and version. (Popular "magic" tags
are "GIF87" or "JPEG", or even "<?xml".) We could use a 32-bit tag such
as "PWS3", or the 64-bit tag "PWSafe30". With this magic value,  
applications
can quickly check whether a file is a Password Safe database or not. And it
allows format updates in the future to be less painful, by not requiring
the app to cycle through all known formats.

As for the fields in a database, I suggest adding a stand-alone "URL"
field, rather than the hack of having the URL among the notes.

Also, this is a good opportunity to change the default character set
to UTF-8 or UTF-16.

Frank

-- 
Frank Pilhofer, [email protected]


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