Current e-mail crypto designs are just asking for trouble. Terry Ritter Only a few different ciphers are used in e-mail crypto products.
Some manufacturers talk of someday allowing users to select from six or eight popular ciphers.
If someone wants to spend time and money attacking a cipher, they are not going to bother with a cipher which protects almost no data. An attacker will select a widely-used cipher, because that has the best payoff. E-mail systems can and should have a common interface and support arbitrary external ciphering routines. In a decade or two we might have tens of thousands of different custom ciphers, any of which might be used by the same e-mail interface. Each of these ciphers will carry only a tiny fraction of the information protected by a widely-used cipher, and so will be much less attractive and much less likely to be attacked and penetrated.