Re: [openpgp] Fingerprints

[Derek Atkins <[e-mail]>]

Christoph Anton Mitterer <[e-mail]> writes:

> On Wed, 2015-04-15 at 16:21 -0400, David Shaw wrote:
>> Using a string is fine, but even with numbers, there is no rule that
>> the number has to be a single byte.  After enough years and algorithms
>> added, it could be "100000:ABCDEF0123..."
> But numbers would make problems if we're using the binary representation
> of the fingerprint (i.e. not the ASCII/UTF8 version of it).
> How should one know where the algo type ends, 0x0 can't be used since it
> may be part of the number.
> So it can only be done if the algo type is defined to be a (null
> terminated) string.

It's easy -- all algorithms are currently defined to be <= 127.  If we
need more than that we can use base-128 encoding.  I.e., the number is
self-length-encoded in a way that you always know when the number ends.

The benefit of using a number instead of a string is that in the vast
majority (probably 99.999%) of use cases we'll be within the 127-value
limitation so we can encode it in exactly one byte.  A string will
always require at least two bytes, and that only gives you ~52 options.

> Cheers,
> Chris.

-derek
-- 
       Derek Atkins                 617-623-3745
       [e-mail]             www.ihtfp.com
       Computer and Internet Security Consultant