entropy

Hal:

Ascii encoding used by PGP reduces this to 6 bits per character (e.g. a character set with 64 printable characters) neglecting line separators and message beginnings and endings. So there should be a little less than 6 bits per character for encrypted, Ascii-encoded messages.

Hal is, of course, right. I was getting myself confused between entropy lost in the encoding and the entropy of the encoding. The channel uses up two bits of entropy per character in the encoding. What's left is six bits. As punishment for getting this so egregiously wrong, I'm going to post some C code for measuring entropy so that you all can play with it. Eric