Patent ID: 7565539

Claim:
A method of establishing a key for encrypted communication over a communication link between a first and a second modem, each modem having a respective first and second master key, comprising: disabling frame encryption and setting a key Id to a first value; generating a first key material for said first modem; transmitting a first message that is encrypted using said first master key, said first message comprising said first key material, from said first modem to said second modem via an unencrypted first frame over said communication link, wherein said first master key is known to the first modem and the second modem prior to the transmitting step; receiving said first key material at said second modem and generating a second key material; at said second modem, after said step of receiving said first key material, sending a second frame including a second message comprising said second key material encrypted using said second master key, to said first modem over said communication link without encrypting said second frame, wherein said second master key is known to the first modem and the second modem prior to the transmitting step; generating session keys at each of said first and second modems based on the first key material and the second key material; programming an encryptor at said first modem with a second key Id and said session key, and programming a decryptor at said second modem with said second key Id and said session key; enabling encryption at said first modem by the encryptor using the second key Id to generate encrypted frames, the encrypted frames including the second key ID, and transmitting information in the encrypted frames to the second modem, and receiving said encrypted frames at said second modem and decrypting said encrypted frames using the decryptor when frames including said second key Id are received.