It encrypts the compressed speech using your choice of the Blowfish, Triple DES, or IDEA block ciphers, and transmits the encrypted packets over the internet or your modem to your friend's computer. At the other end, the process is reversed. Either user can hit a key to switch between talking and listening. Earlier versions of Nautilus generated an encryption key from a shared secret passphrase that you and your friend would choose together ahead of time. Beginning with version 1.5, Nautilus generates the encryption key using the Diffie-Hellman key exchange algorithm by default, although users may still revert to the secret passphrase method if they prefer.
Further details are in the documentation file included with the program.
Nautilus is available in three different formats. As a DOS executable, it is available as an archive in zip format along with it's associated documentation. We don't like this law but have to abide by it while it is in effect. Nautilus is distributed through export-restricted FTP sites for this reason. Export it at your own risk.