Patent ID: 6876292

Claim:
An electronic key system for a vehicle comprising: an electronic key having first ID (identification data), second ID, and third ID which is shorter in data length than the second ID, said electronic key outputting the first ID, the second ID, and the third ID; and an on-vehicle apparatus communicating with said electronic key by means of wireless communication, said on-vehicle apparatus having fourth ID, fifth ID, and sixth ID which is shorter in data length than the fifth ID, said on-vehicle apparatus permitting starting an engine of the vehicle when one of first and second conditions is achieved, the first condition including a condition that the second ID outputted from said electronic key corresponds with the fifth ID, the second condition including a condition that the first ID outputted from said electronic key corresponds with the fourth ID and the third ID outputted from said electronic key corresponds with the sixth ID, said on-vehicle apparatus requesting said electronic key to output the third ID when the first ID corresponds with the fourth ID and when an operator carrying said electronic key executes an operation for starting the engine.