Re: Partial chunking question

[David Shaw <dshaw@xxxxxxxxxxxxxxx>]

On Thu, Aug 05, 2004 at 01:53:40PM -0400, Hasnain Mujtaba wrote:

> I had a question on breaking data into partial chunks. If someone can
> clarify this, I'd appreciate it:
> 
> Suppose the chunk size you are using is 8192 bytes and the final data
> chunk is less than 8192, say it is 6480. My chunking implementation puts
> these final 6480 bytes into one non-partial length chunk so that the
> chunk sequence looks like this: 8192, 8192, ... , 8192, 6480.
> 
> GPG and PGP, however, break this final data into power of two lengths,
> i.e 8192, 8192, ... , 8192, 4096, 2048, 336. 
> 
> My approach interoperates with both GPG and PGP. But I am curious as to
> why GPG and PGP break the final data this way, rather than putting it
> all in one final non-partial chunk. I hope I have not overlooked some
> RFC requirements.

It's not an RFC requirement.  When writing a stream, GnuPG picks the
largest possible power of 2 for the amount of data it is ready to
write at that point.  I suspect PGP does something similar for similar
reasons.

What you are doing is also perfectly legal.

David