The installation method makes possible the installation of new programs, while
maintaining security, in a system LSI device. The installation method comprises
a step for receiving the signature data 7 of a program 6, a step
for checking for interference with other already installed programs on the basis
of said signature data 7, and a step for authorizing the installation of
programs with which there is no interference. A declaration of signature data is
elicited from a program being installed; a check for interference among programs
is performed based on this, authentication is performed, and the installation of
interfering programs is prevented or the installation of programs with which there
is no interference is executed. It therefore becomes possible to install new programs
while protecting high-security programs.