PGP & GPG

162 Chapter 11

encryption algorithms. Too, different versions of OpenPGP

programs might prefer to use different algorithms. Generally

speaking, the best way to ensure that your software can com-

municate with any other OpenPGP software is to install all the

algorithms and hash methods available. Some of these hashes

are insecure, and could be forged—particularly MD5, and to a

lesser extent SHA-1. People who use these are not as secure as

they believe, but you can choose to communicate with them if

you wish.

This still leaves the problem of pre-OpenPGP versions of

PGP that don’t use 3DES. These older versions almost always

have security problems, ...