ThisApplicationNotecoversfourencryption
algorithms:AES,XTEA,SKIPJACK
®
andasimple
encryptionalgorithmusingapseudo-randombinary
sequencegenerator.Thescienceofcryptography
datesbacktoancientEgypt.Intoday’seraofinforma-
tiontechnologywheredataiswidelyaccessible,
sensitivematerial,especiallyelectronicdata,needsto
beencryptedfortheuser’sprotection.Forexample,a
network-basedcardentrydoorsystemthatlogsthe
personswhohaveenteredthebuildingmaybesuscep-
tibletoanattackwheretheuserinformationcanbe
stolenormanipulatedbysniffingorspoofingthelink
betweentheprocessorandthememorystorage
device.Iftheinformationisencryptedfirst,ithasa
betterchanceofremainingsecure.Manyencryption
algorithmsprovideprotectionagainstsomeonereading
thehiddendata,aswellasprovidingprotectionagainst
tampering.Inmostalgorithms,thedecryptionprocess
willcausetheentireblockofinformationtobe
destroyedifthereisasinglebiterrorintheblockprior
todecryption.AN953DataEncryptionRoutinesforthePIC18Author:DavidFlowersENCRYPTIONMODULEOVERVIEWMicrochipTechnologyInc.Fouralgorithmstochoosefrom,eachwiththeirownbenefitsINTRODUCTIONAdvancedEncryptionStandard(AES)ThisApplicationNotecoversfourencryption-ModulesavailableinC,Assemblyandalgorithms:AES,XTEA,SKIPJACKandasimpleAssemblywrittenforCencryptionalgorithmusingapseudo-random
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