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Multiple messages + entropy

The Internet PEM (Privacy Enhanced Mail) standard uses the
concept which Dean Tribble mentioned of multiple encryption
(using each recipient's public key) of a single session key
which encrypts the message.  PGP's data structures do not
currently provide for this but could be extended pretty easily
to allow it.

On the entropy measure - I thought entropy was how many bits
of information you get per character.  Encrypted binary text
would be pretty close to 8 bits per character.  The RFC1113
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.

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