Electrical computers and digital processing systems: support – Computer program modification detection by cryptography
Reexamination Certificate
2006-02-10
2008-11-04
Kincaid, Kristine (Department: 2139)
Electrical computers and digital processing systems: support
Computer program modification detection by cryptography
C713S193000, C713S194000, C726S026000, C726S027000
Reexamination Certificate
active
07447912
ABSTRACT:
Oblivious checking of a digital good is performed by identifying a plurality of key instructions within a function of a digital good. Each key instruction is an instruction that possibly modifies a register or a flag. An extra instruction is then inserted into the function for each of the key instructions. The extra instructions each correspond to one of the key instructions and modify a register in a deterministic fashion based on the corresponding key instruction. A set of inputs to the function are then identified that result in different valid computation paths in the function being taken. A checksum for the function is then generated by using a mapping function which maps the contents of the register to the set of inputs.
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Jakubowski Mariusz H.
Venkatesan Ramarathnam
Kincaid Kristine
Lee & Hayes PLLC
Microsoft Corporation
Shaw Yin-Chen
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