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10. Decoding

The basic way to decode encrypted messages is to use premail -decode as a command line. You can either give a filename as an argument, or premail will accept the encrypted message on its standard input. In either case, the decoded message will be printed on the standard output.

The message can be a standard e-mail message (RFC 822 format), or it can be an entire mailbox. In the latter case, premail will decode each of the messages individually. If you don't have premail directly integrated into your mailer, then here's a handy way to view your mail:

premail -decode $MAIL | more

If the message is actually encrypted, then premail will need to access the secrets file. If you are logged out of premail, then premail will try to open an xterm window for you to type the passphrase for the secrets file. If that doesn't succeed, premail will print an error message. At that point, you might choose to log in (i.e. premail -login) and then try the decoding again.

If, as in many mailers, you have easy access to the body of the message but not the header, then you can use premail -decode -body on the body. This works well for plain PGP encrypted messages, but unfortunately does not work for MIME-based message formats, because important information is contained in the header.

The results of the decoding (including signature verification) are given in an X-Premail-Auth: header field. This header field is protected against forgery; if the original message contains it, it is changed to X-Attempted-Auth-Forgery.


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