A wireless mobile unit includes a voice encoder circuit that receives an
analog voice signal and creates digital voice data representing a user's
voice. The mobile unit receives an encryption key entered by the user,
typically on the keypad or through a voice recognition circuit, and stores
the encryption key in a storage device. An encryption circuit encrypts the
digital voice data using the encryption key. A transmitter then modulates
the encrypted voice data onto an RF signal and transmits the RF signal to
a base station in a wireless network. The base station uses the same
encryption key to decrypt the signal before transmitting it to another
base station or mobile unit. Signals transmitted from the base station to
the mobile unit are encrypted and decrypted using a user-selected
encryption key in a similar manner.
