hap -- my version of "hashapass"

(play with it online here)

This is my version of 'hashapass' (see http://hashapass.com/cmd.html). The main differences are:

• our keys default to 14 characters, not 8
• but you can choose any key length you want
• what they call "parameter" we call "domain name" or "domain"
• we may suffix a "salt" to the domain. See below for why we use a salt.

If you want to compare 'hap' to hashapass command line, this one is, in bash:

echo -n "$domain$salt" |
    openssl sha1 -binary -hmac "$mp" |
    openssl base64 |
    cut -c1-${pwlen:-14}

The salt helps when you are forced to change passwords for a domain. It effectively makes the domain name different. Note that the salt does NOT have to be kept secret, in terms of security.

If $DISPLAY is set, this program also uses the 'xsel' command to dump the generated password into the X selection buffer, and then -- once you hit enter to confirm you're done -- to clear it out.