Methods of securely communicating a message from a first terminal to a second terminal include generating a keypad including a random sequence of bits having a length L, encrypting the message at the first terminal using a bit string beginning at an offset O in the keypad, and transmitting the encrypted message and an indicator of the offset O to the second terminal. A communication terminal includes a controller, a communication module configured to establish a location-limited communication channel, and an encryption unit configured to store a keypad including a random sequence of bits having a length L, to encrypt an outgoing message using the keypad, and to decrypt an incoming message using the keypad.