System and method for protecting integrity of alterable ROM using digital signatures
First Claim
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1. A system, comprising:
- a processor;
a storage device storing an operating system program for execution on the processor;
an alterable read only memory for storing data; and
a corruption detection device for detecting unauthorized changes to data in the alterable read only memory, the corruption detection device reading a signature, encrypted with a private key, that represents a non-corrupted version of data in the alterable read only memory, and further reading, from a secure memory location, a public key for decrypting the signature, the corruption detection device operating to compare the decrypted using public key, signature to a computed signature for detecting an occurrence of an unauthorized change to the data in the alterable read only memory.
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Abstract
A system and method for verifying the integrity of a computer system'"'"'s BIOS programs stored in alterable read only memory (such as FLASH ROM), and preventing malicious alteration thereof. The system and method regularly check the contents of the alterable read only memory using a digital signature encrypted by means of an asymmetrical key cryptosystem.
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Citations
28 Claims
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1. A system, comprising:
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a processor; a storage device storing an operating system program for execution on the processor; an alterable read only memory for storing data; and a corruption detection device for detecting unauthorized changes to data in the alterable read only memory, the corruption detection device reading a signature, encrypted with a private key, that represents a non-corrupted version of data in the alterable read only memory, and further reading, from a secure memory location, a public key for decrypting the signature, the corruption detection device operating to compare the decrypted using public key, signature to a computed signature for detecting an occurrence of an unauthorized change to the data in the alterable read only memory. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method, comprising the steps of:
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storing data in an alterable read only memory of a computer system; storing in a first memory location in the system an encrypted signature representing a valid copy of the data in the alterable read only memory; storing in a second memory location in the system a public key to the encrypted signature; in response to a triggering event, computing a current signature for the data stored in the alterable read only memory, decrypting the signature representing the valid copy using the public key, and comparing the decrypted signature and the current signature to determine the validity of the data stored in the alterable read only memory. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A method for operating a data processing system, comprising steps of:
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partitioning a bootstrap program between an unalterable read only memory device and an alterable memory device; storing, in the alterable memory device, private key encrypted validity data representing a portion of the bootstrap program stored in the alterable memory device; storing, in the unalterable read only memory device, a public key for decrypting the private key encrypted validity data; in response to a triggering event, executing a portion of the bootstrap program stored in the unalterable read only memory device, the executed portion of the bootstrap program first computing validity data for at least some of the content of the alterable memory device, then using the stored public key to decrypt the private key encrypted validity data, and then comparing the decrypted validity data to the computed validity data; and transferring control of the bootstrap program from the portion stored in the unalterable read only memory device to the portion stored in the alterable memory device only if the result of the comparison indicates that no unauthorized modifications have been made to the content of the alterable memory device. - View Dependent Claims (28)
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Specification