Patent ID: 7284134

Claim:
A method for installing a secret key in a Large Scale Integration device, comprising a step of bonding a second Large Scale Integration device to a first Large Scale Integration device, wherein the first Large Scale Integration device comprises: a memory part for storing a first secret key; first and second external input terminals; a selector having an input for receiving the first secret key and other input connected with the first external input terminal, the selector having a selection signal input connected with the second external input terminal; and a processing circuit using an output of the selector as the secret key, the second Large Scale Integration device comprises: a memory part for storing a second secret key; first external output terminal from which the second secret key is output; and a second external output terminal from which a selection signal is output, the selection signal being set so that the selector of the first Large Scale Integration device selects and outputs the other input, and the step of bonding comprises bonding the second Large Scale Integration device to the first Large Scale Integration device so that the first and second external output terminals of the second Large Scale Integration device are connected to the first and second external input terminals of the first Large Scale Integration device, respectively.