A system and method for generating and authenticating a password to protect a computer system from unauthorized access. The characters of the password are placed in data packets by an access device. Prior to sending the packets, the device inserts a predefined number of blank packets between each of the character-carrying packets. The number of blank packets is retrieved from a number sequence that is shared between the access device and an authentication device. The authentication device determines whether the received set of password characters matches a stored set of password characters, determines whether the received number of blank packets between the received character-carrying packets matches a predefined number of blank packets, and positively authenticates the access device only if both conditions are met.