More importantly, end-to-end encryption means that your desktop/laptop/tablet/phone/TI-83 is doing the crypto, especially signatures.

On a somewhat related note, I remember reading some documentation on a one-time password scheme, which I can't find anymore. It briefly mentioned something about using DES calculators to handle crypto signatures (for what reason i cannot remember). For our purposes, a PGP/GPG hand-held device would be neat, though perhaps cumbersome to actually user.