使用pic17c42实现数据加密标准

InJanuary1977,TheUnitedStatesgovernment

adoptedaproductcipherdevelopedbyIBMasitsoffi-

cialencryptionstandard[1].Thisalgorithm,calledthe

DataEncryptionStandard(DES),hasbeenadoptedas

aworldwidestandardfordataencryptionbyISO(Inter-

nationalStandardsOrganization)[2,3].Thisapplica-

tionnotedescribestheimplementationoftheDES

algorithmonPIC17C42.AN583ImplementationoftheDataEncryptionStandardUsingPIC17C42Authors:AlLovrichKEYSCHEDULEMarkPalmerTheDESusesa64-bitkeyforencryptionanddecryp-MicrochipTechnologyInc.tionprocess.Initially,theoriginal64-bitkeyisreducedto56-bitbyignoringeveryeighthbit.IngeneraltheseINTRODUCTIONbitsareusedasparitybitstomakesurethattherewere