Patent ID: 8392724
Filing Date: 2013-03-05
Classification: G06F

Abstract:
1. An information terminal for executing a program, comprising: an update certificate obtaining unit operable to obtain an update certificate including an old characteristic value and a new characteristic value, the old characteristic value being extracted from an old program and indicating a characteristic of the old program, the new characteristic value being extracted from a new program that is obtained by updating the old program and indicating a characteristic of the new program; a holding unit operable to hold data and a past characteristic value in association with each other, the past characteristic value being extracted from a past program and indicating a characteristic of the past program, the past program being a program that used the data in past; a judging unit operable to judge, using the new characteristic value, whether or not a current program matches the new program, the current program being a program that is currently executed in the information terminal; and a permission unit operable to judge, in accordance with the old characteristic value and the past characteristic value, whether or not the data can be used when the judging unit judges that the current program matches the new program, and permit the current program to use the data when judging that the data can be used, wherein the new characteristic value is a digest of the new program, wherein the judging unit includes: wherein the old characteristic value is a digest of the old program, wherein the past characteristic value is a digest of the past program, wherein the data is associated with a use condition value that is a value based on the digest of the past program, wherein the digest generating sub-unit generates a digest of each of one or more programs that were executed in a predetermined order before the current program is executed, wherein the permission unit includes: wherein the extend value generating sub-unit (i) generates the pre-update extend value when the judging unit judges that the current program matches the new program, and (ii) generates a current extend value by performing an extend calculation on each digest of the one or more programs and on the digest of the current program when the judging unit judges that the current program does not match the new program, wherein the extend value judging sub-unit (i) judges whether or not the use condition value matches the pre-update extend value when the judging unit judges that the current program matches the new program, and (ii) judges whether or not the use condition value matches the current extend value when the judging unit judges that the current program does not match the new program, and wherein the use permission sub-unit permits the current program to use the data when the extend value judging sub-unit judges that the use condition value matches either the pre-update extend value or the current extend value.