dh question

Paul Crowley paul at ciphergoth.org
Tue Jun 7 16:06:50 PDT 2005

Brad Fitzpatrick wrote:
> Which means it should be defined, right?  The different times this comes
> up aren't purely implementor-only decisions... they affect the other
> party.

It's said "All integers are represented in big-endian signed two's 
complement, Base64 encoded" for a while now...

> I'll go with 2's complement MSB, then, if you add it to the spec.  Unless
> that's silly and we can ignore negative numbers.

It's kind-of silly, but it's a common format.  At least I know of two 
places where it's used - SPKI and Java.  Perl doesn't seem to have a way 
of converting between bytes and bigints.

> I'm concerned where people's libraries may do one thing vs. another for
> them and they might not have ways to change it?  No clue.

Since they're always non-negative, our integers can always be 
interpreted by something that's not expecting 2~.  If we need to make 
something 2~ we can do it by conditionally adding a zero byte to the 
beginning if the high bit is set.
\/ o\ Paul Crowley, paul at ciphergoth.org
/\__/ http://www.ciphergoth.org/

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