7
6. How Preboot BIOS Implements the Password Filter And
Handles Dead Keys
TheHPBIOSimplementsasecondlevelpasswordfiltertofurtherpreventthe
lock‐outsituation.
HPBIOSPrebootandHPDriveEncryptioncontainthekeyboardmappingsfor
allthesupportedkeyboardslistedabove.WhenauserissettingupPreboot
SecuritywiththeBIOSPrebootorDriveEncryptionlevelsenabled,orwhena
userchangeshis/herpassword,theBIOSPrebootandDriveEncryption
receivestheUnicodepasswordfromtheOS.TheBIOSisresponsibleto
guaranteethatthekeyboardbeingassociatedwiththatuserisabletotypethe
password.Otherwise,theBIOSwillrejectthepassword.However,therestill
maybeaninstancewheretheuserchangesthekeyboardinWindowswithout
theBIOS’sknowledgeorwhentheuserisnotawareofthekeyboardlayout
currentlyinuse.Tocompensateforthesituationwheretheusermaynotbe
abletophysicallytypetheirpasswordduetothesetwosituations,theBIOSwill
automaticallyprovidetheusertheabilityto“click”outher/hispasswordafter
failingwiththephysicalkeyboard.Thisisdonebyshowingeverycharacteron
thescreenthatcouldbetypedwiththekeyboardcurrentlyassociatedwiththe
user,eachofthemasbuttonsandwhichcanbeclickedwiththemousetoform
thepassword.Thismethodprovidesawayfortheusertoenterthepassword
withoutthephysicalkeyboard.
(Pleasenote:Whenusingthe“On‐ScreenKeyboard”intheBIOS,therearemanycharactersshownandsomecharacters
maylookverysimilartoothersonsomekeyboards.Ifexperiencingtroubleusingthisfeature,sopleaselookatallof
thecharactersbeforeclickingoutyourpasswordtoensureyouareenteringthecorrectcharacters.)
IntheBIOS,theuseofDeadKeyshasalsobeenaddedtotrytoprovidetheuser
withasmuchkeyboardfunctionalityaspossible.Ifforsomereasonacertain
characterisproducedontheOSlevelthatcannotbetypedintheBIOS,thiswill
causethepasswordchangetoberejected.Unlessrejected,theusershouldfeel
safeandconfidentinusingDeadKeysforpasswordsassociatedwiththe
PrebootSecurityfeature.
ThisabilityofthePrebootSecurityhingesonitsabilitytoensurethatthe
WindowspasswordcanalwaysbeenteredinthePrebootBIOSandDrive
Encryption,andthereforeallcharactersthatrequirespecialtypingmethods
thatarenotcommontoallkeyboards,suchastheuseoftheKanakeyortheuse
ofIMEfunctionofWindows,willresultinthepasswordchangebeingrejected
fromtheBIOS,astheBIOSdoesnotcontaintheseadvancedtypingfeatures.