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A secure LSI device 1 includes an encryption section 2 for encrypting a program, and an external I/F 50 for inputting/outputting a program or data from/to an external memory 100. In the encryption section 2, the operation of a private key arithmetic processing section 20 is prohibited with respect t

A secure LSI device 1 includes an encryption section 2 for encrypting a program, and an external I/F 50 for inputting/outputting a program or data from/to an external memory 100. In the encryption section 2, the operation of a private key arithmetic processing section 20 is prohibited with respect to a sequence whose execution is determined by a key-generation/update sequencer 30 to be impermissible. In the external I/F 50, a program processing section 51 and a data processing section 55 are structured independently from each other.

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1. A semiconductor device comprising: a boot ROM for storing a boot program;a mode ID storage section for storing a mode ID, the mode ID indicating as a current operation mode, a product operation mode for operating as a product device, or a development mode for developing a program; anda program ve

1. A semiconductor device comprising: a boot ROM for storing a boot program;a mode ID storage section for storing a mode ID, the mode ID indicating as a current operation mode, a product operation mode for operating as a product device, or a development mode for developing a program; anda program verification section for verifying a validity of an external program stored in an external memory,wherein a sequence of the boot program is controlled in accordance with the current operation mode indicated by the mode ID stored in the mode ID storage section, andwherein when the mode ID indicates the development mode, the external program stored in the external memory is executable, while when the mode ID indicates the product operation mode, the external program is executed only if the validity of the external program is verified by the program verification section. 2. The semiconductor device of claim 1, wherein the boot program reads the external program the validity of which is verified by the program verification section into the semiconductor device. 3. The semiconductor device of claim 1, wherein the mode ID storage section stores the mode ID in an unrewritable state. 4. The semiconductor device of claim 3, further comprising a flag for controlling whether rewriting of the mode ID storage section is permitted or not, wherein when the mode ID is written into the mode ID storage section, a predetermined value is set at the flag and the mode ID storage section becomes in the unrewritable state. 5. The semiconductor device of claim 1, further comprising a mode ID storage register, wherein the boot program sets the mode ID stored in the mode ID storage section at the mode ID storage register. 6. The semiconductor device of claim 5, wherein the boot program has a first sequence common to operation modes and a second sequence different at every operation mode, and wherein at the first sequence, the mode ID is set at the mode ID storage register. 7. The semiconductor device of claim 1, further comprising a key processing section for storing a parameter required for decrypting program or data at the product operation mode, wherein the boot program sets the parameter at the key processing section. 8. The semiconductor device of claim 1, wherein the program verification section calculates a HASH value of the external program and compares the calculated HASH value with a prestored HASH value to verify the validity of the external program. 9. The semiconductor device of claim 1, wherein the external memory is a flash memory, and the semiconductor device further comprising an interface section for reading in program and data from the flash memory. 10. The semiconductor device of claim 1, wherein at the product operation mode, the external program is stored in the external memory in a encrypted state with a inherent key unique to the semiconductor device. 11. A method of booting a semiconductor device, wherein the semiconductor device comprises a mode ID storage section for storing a mode ID, the mode ID indicating as a current operation mode, a product operation mode for operating as a product device, or a development mode for developing a program,the method comprising the steps of: booting up a boot program in a boot ROM;determining, by a execution of the boot program, the current operation mode indicated by the mode ID stored in the mode ID storage section; andverifying, by the execution of the boot program, a validity of an external program stored in an external memory,wherein when the mode ID indicates the development mode, an operation of the semiconductor device proceeds to the external program, while when the mode ID indicates the product operation mode, only if the validity of the external program has been verified, the operation of the semiconductor device proceeds to the external program. 12. The method of claim 11, further comprising a step of reading the external program the validity of which is verified into the semiconductor device. 13. The method of claim 11, wherein the mode ID storage section stores the mode ID in an unrewritable state. 14. The method of claim 13, wherein when the mode ID is written into the mode ID storage section, a predetermined value is set at a flag for controlling whether rewriting of the mode ID storage section is permitted or not and the mode ID storage section becomes in the unrewritable state. 15. The method of claim 11, further comprising a step of setting, by the execution of the boot program, the mode ID stored in the mode ID storage section at a mode ID storage register in the semiconductor device. 16. The method of claim 15, wherein the boot program has a first sequence common to operation modes and a second sequence different at every operation mode, and wherein at the first sequence, the mode ID is set at the mode ID storage register. 17. The method of claim 11, further comprising a step of setting, by the execution of the boot program, a parameter required for decrypting program or data when the mode ID indicates the product operation mode. 18. The method of claim 11, further comprising a step of calculating a HASH value of the external program and comparing the calculated HASH value with a prestored HASH value to verify the validity of the external program. 19. The method of claim 11, wherein at the product operation mode, the external program is stored in the external memory in a encrypted state with a inherent key unique to the semiconductor device.