Integrity Protection VIRUS badFile goodFile ①小e①ites BigFirmTM hash(goodFile) User Software manufacturer wants to ensure that the executable file is received by users without modification... Sends out the file to users and publishes its hash in NY Times The goal is integrity,not secrecy Idea:given goodFile and hash(goodFile), very hard to find badFile such that hash(goodFile)-hash(badFile) 33 Integrity Protection Software manufacturer wants to ensure that the executable file is received by users without modification… Sends out the file to users and publishes its hash in NY Times The goal is integrity, not secrecy Idea: given goodFile and hash(goodFile), very hard to find badFile such that hash(goodFile)=hash(badFile) goodFile BigFirm™ User VIRUS badFile The Times hash(goodFile)