Patent ID: 7515715

Claim:
A method for encrypting a Mode-S extended squitter, the Mode-S extended squitter including an eight-bit control segment followed by a twenty-four bit sender address segment, a fifty-six-bit message segment and a twenty-four-bit parity/identity segment, the method comprising: providing a key, the key including a control key segment, an address key segment, a first message key segment, and a first parity/identity key segment; adding modulo two the control segment to the control key segment to produce an intermediate control segment; adding modulo two the address segment to the address key segment to produce an intermediate address segment; adding modulo two the message segment to the first message key segment to produce an intermediate message segment; adding modulo two the parity/identity segment to the first parity/identity key segment to produce an first intermediate parity/identity segment; concatenating the intermediate control segment, the intermediate address segment, the intermediate message segment, and the intermediate parity/identity segment to produce an intermediate extended squitter; shifting the intermediate extended squitter according to a linear function shift register to produce a shifted-intermediate parity/identity segment; wherein the key further includes a second message key segment, and a second parity/identity key segment; adding modulo two the message segment to the second message key segment to generate an encrypted message segment; adding modulo two the shifted-intermediate parity segment to the second parity key to generate a doubly-encrypted parity/identity segment; and concatenating the control segment, the address segment, the encrypted message segment and the doubly-encrypted parity/identity segment to produce an encrypted extended squitter.