What compatibility issues exist between PGP 5.x and earlier versions?
PGP 5.0 introduces some new algorithms for both public key and conventional encryption. These changes are good from both technical (security & efficiency) and political (patent) standpoints. With the death of the Diffie-Hellman key exchange patent, the freeware PGP new algorithms are 100% free of patent problems, and free of legalese such as come with the RSAREF toolkit. The Diffie-Hellman key exchange key size limit is also larger than the old RSA limit, so PGP encryption is actually more secure, now. The new SHA1 hash function is better than MD5, so signatures are more secure, now, too. The conventional encryption used is all sound, and definitely not the weak link in the chain. This much is good news. The bad news, of course, is that there will be some interoperability problems, since no earlier versions of PGP can handle these algorithms. How this affects you depends on the PGP version that you have. There are really 3 versions of PGP called PGP 5.0. The freeware edition can only g
