Re: Revised formatv3 description

On Mon, 16 Jan 2006 16:01:25 -0500, Rony Shapiro <[email protected]> wrote:
>
> In light of Frank's comments and some experience I've gained from actual
> implementation, here's a revised version of the format description.
>

Hi Rony,

thanks for the work you're putting into this. The document is shaping up
quite nicely. Three more comments:

>
> 2.8.1 HDR: The database header. All data in the header is written in
> fields, as defined in Section 3. The first field contains the version
> number of the database format. For this version, the value is 0x0300
> (stored in little-endian format, that is, 0x0003).
>

Personally, I find the "0x0003" confusing. Maybe "0x00 0x03" would be
clearer.

>
> 2.10 HMAC: The 256-bit keyed-hash MAC, as described in RFC2104. The value
> is calculated over all of the plaintext fields, that is, over all the  
> data
> stored in all fields (starting from the version number in the header,
> ending with the last field of the last record). The key L as stored in B3
> and B4 is used as the hash key value.
>

Reading RFC2104, I find that it requires a separate definition of the hash
function that is used:

    This document specifies HMAC using a generic cryptographic hash
    function (denoted by H). Specific instantiations of HMAC need to
    define a particular hash function.

So you should say something like

   2.10 HMAC-SHA256: The 256-bit keyed-hash MAC, as described in RFC2104,
   using SHA256 as its hash function.

>
> 3.1 Field types (based on the v2 format):
>

Please add, from formatV2.txt:

    Timestamps are stored as 32 bit, little endian, unsigned integers,
    representing the number of seconds since Midnight, January 1, 1970,	
    GMT. (This is equivalent to the time_t type on Windows and POSIX.
    On the Macintosh, the value needs to be adjusted by the constant
    value 2082844800 to account for the different epoch of its time_t
    type.)

Frank

-- 
Frank Pilhofer, [email protected]


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