Isolation of non-secure software from secure software to limit virus infection
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Citation (published version)Greg Blonder. "Isolation of non-secure software from secure software to limit virus infection." U.S. Patent 5,802,275-A.
A personal digital assistant (PDA) receives and executes both encrypted and unencrypted programs. Encrypted programs are fairly secure from virus infection, while unencrypted programs are not. To prevent contamination of the PDA with infected encrypted programs, only those encrypted programs that are keyed to the individual PDA's unique device identifier can be decrypted and executed by that PDA. To prevent non-secure programs from corrupting secure programs and their data, programs that were received unencrypted are prevented from modifying programs that were received encrypted as well as data generated by their execution. When a user suspects a virus infection, the user pushes a special button on the PDA that prevents execution of programs that were received unencrypted and hence are suspected of being infected, while allowing continued execution of programs that were received encrypted and hence are presumed to be secure.