Method for preventing unauthorized modification of data in a dev

Details Method for preventing unauthorized modification of data in a dev Method for preventing unauthorized modification of data in a dev

1994-12-08

1997-10-14

Chan, Eddie P.

G06F 1214

Patent

active

056780273

ABSTRACT:
A method for preventing unauthorized data modification is carried out in a device, such as a chip card, having a nonvolatile memory, a central processing unit, and a program memory assigned to the central processing unit. A command is given to set a check bit in a check register being triggerable by the central processing unit, with a program for modifying data in a memory region of the nonvolatile memory. A check is made to determine if the command derives from a defined address region of the data modification program. The command is carried out by setting the check bit in the check register, if the command derives from the defined address region. A check is made for special permission for a data modification in a memory region of the nonvolatile memory. A check is made to determine if the check bit is set, if the special permission has been given. The data in the memory region is modified if a control bit is set. The check bit in the check register is reset and the permission to write is rescinded, after an allowed data modification, or if a data modification was not allowed, or if no check bit was set.

REFERENCES:
patent: 3742458 (1973-06-01), Inoue et al.
patent: 5325496 (1994-06-01), Hays et al.
patent: 5452431 (1995-09-01), Bournas
Patents Abstract of Japan, Section No. P 1531, vol. 17, No. 228, May 11, 1993 & JP-4-357543 (Fujitsu) p. 47.
Patents Abstact of Japan, Section No. P 14, vol. 4, No. 78, Jun. 6, 1980 & JP-5542312 (Hitachi) p. 28.

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