Problems with key available in v1.4.19 but not v2.1.5

[Robert J. Hansen]

> I'm having some problems with my key that was created a long time
> ago (1994) but updated with new emails over the years.

You're using a key generated with PGP 2, which conforms to RFC1991.
This is an *old* *old* standard, and has been pretty much completely
replaced by RFC4880.

Older versions of GnuPG supported RFC1991.  Current versions of GnuPG
have much less in the way of support for RFC1991.

I'd suggest generating a new certificate -- after 20 years you're due
for one.  :)

> Why would v1.4.19 show my pub and sec keys but v2.1.5 wouldn't?  I 
> presume this is something very basic but I'm stumped.  I thought
> v1.x and v2.x keys were interoperable??

RFC4880 keys are interoperable between versions.  RFC1991 keys *aren't*.

RFC1991 has an unfortunate dependency on the MD5 hash algorithm, and MD5
is pretty much completely broken for cryptographic purposes.  Since MD5
is broken, current versions of GnuPG refuse to process MD5 data... which
means RFC1991 support is severely curtailed.