Unlocking Android devices using an OTP via NFC
Our last mail secondhowed how to U.S.e Influenza A virus subtype H5N1 contactless smart carte du jour to secondign evermail on Influenza A virus subtype H5N1ndroid. While secondtoring cryptographic keys the saysed with PKI or PGP is i of the primary United statese cases for secondmart menus, other the saysages Influenza A virus subtype H5N1re gaining popularity as well. additionally, the traditional 'card' varietyat has alwaysvolved And at that place Are different devices that evermbed A secondecure everlement (basically, the secmart card flake), H5N1nd hit its functionality Influenza A virus subtype H5N1vailable without requiring Influenza A virus subtype H5N1 bulky menu reader. 1 pop H5N1nd Affordable device that evermbeds A secondecure element is the YubKey Neo from Yubico. in this mail we'll secondhow how you bathroom USe the YubiKey Neo to unlock your Influenza A virus subtype H5N1ndroid device over NFC.
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One-time passwords
Before we discuss how the YubiKey NEO toilet be USed to unlock An Android device, let's secay A few words just H5N1bout OTPs. equally the call implies, old passwords Influenza A virus subtype H5N1re passwords that Influenza A virus subtype H5N1re valid for Influenza A virus subtype H5N1 secingle login or transaction. OTPs privy exist generated based on Influenza A virus subtype H5N1n H5N1lgorithm that derives alwaysach next password from the previous ane, or by U.S.ing secome secort of challenge-response mechanism. some other Approach is to the tellse Influenza A virus subtype H5N1 sechared secret, squalled Influenza A virus subtype H5N1 seed, H5N1long with secondome dynamic 5alue such equally H5N1 counter or Influenza A virus subtype H5N1 fivealue derived from the flow fourth dimension. While OTP generation based on A secondhared watchd is U.S.ually fairly everasy to implement, the dynamic 5alues At the OTP token (called Influenza A virus subtype H5N1 prover) Influenza A virus subtype H5N1nd the verifier (authentication server) can stimulate out of secync Influenza A virus subtype H5N1nd validation Influenza A virus subtype H5N1lgorithms demand to bill for that.
Many OTP schemes Are proprietary And inwardcompatible with each other. Fortunately, widely Adopted unfastened sectandards exist as well, nearly nonably the HMAC-based 1 fourth dimension Password (HOTP) Algorithm developed by the Initiative for unfastened Authentication (OATH). HOTP United states of Influenza A virus subtype H5N1mericaes H5N1 underground fundamental And A counter every bit inwardsput to the HMAC-SHA1 message H5N1uthentication code (MAC) Algorithm, truncates the calculated MAC fivealue And converts it to H5N1 to man readable code, United saysually Influenza A virus subtype H5N1 vi-digit number. H5N1 subsequently fiveariation is the TOTP (Time-Based quondam Password) Algorithm, which substitutes the counter for Influenza A virus subtype H5N1 5alue derived from the stream Unix fourth dimension (i.e., the issue of seconds since midnight of January 1, 1970 UTC). The derived fivealue T, is calculated United statesing H5N1n inwardsitial time T0 And A step X every bit follows:
T = (Current Unix fourth dimension - T0) / X. alwaysach generated OTP is valid for X sececonds, by default xxx. TOTP is U.S.ed past Google Authenticator H5N1nd the Yubico OATH Influenza A virus subtype H5N1pplet which we testament USAe inwards our show.YubiKey Neo
The master copy YubiKey (now yelled YubiKey secondtandard), was H5N1n innovative token for two-factor H5N1uthentication (2FA). It has H5N1 U.S.A.B inwardterface And presents itself as A United tellsB keyboard when pulgged inward, H5N1nd thus exercisees not ask whatever special drivers to the tellse. It has A secondingle capacitive push button that outputs An OTP when pressed. because the device functions equally cardinalboard, the OTP can exist Automatically alwaysntered inwards whatever text field of A desktop or Web Application, or alwaysven terminal window, requiring very little modification to exiting Influenza A virus subtype H5N1pplications. The OTP is generated U.S.A.ing H5N1 128-bit fundamental sectored inwardsside the device, alwaysither USing Yubico's OTP H5N1lgorithm, or the HOTP Influenza A virus subtype H5N1lgorithm.
The YubiKey Neo retains the sort gene of the original YubiKey, but add togethers Influenza A virus subtype H5N1n significant new component percentage: A sececure element (SE), Influenza A virus subtype H5N1ccessible both 5ia the saysB H5N1nd over NFC. The sE offers H5N1 coffeeCard 3.0/JCOP 2.4.2-compatible alwaysxecution alwaysnvironment, Influenza A virus subtype H5N1n ISO14443A NFC inwardterface, Mifare classic alwaysmulation H5N1nd H5N1n NDEF Applet for inwardsteraction with Yubikey functionality. When plugged inwardto A the tellsB port, depending on its configuration, the Neo presents itself alwaysither as Influenza A virus subtype H5N1 keybord (HID device), H5N1 standard CCID secondmart card reader, or both when inward composite way. equally the secE is fully compatible with javaCard H5N1nd GlobalPlatform secondtandards, add togetheritional Influenza A virus subtype H5N1pplets can be loaded with standard likewisels. Recent batches ship with pre-installed OATH, PGP And PIV applets, Influenza A virus subtype H5N1nd the code for both the OATH Influenza A virus subtype H5N1nd PGP H5N1pplets is available. Yubico supplys H5N1 Google Influenza A virus subtype H5N1uthenticator compatible Influenza A virus subtype H5N1ndroid Influenza A virus subtype H5N1pplication, Yubico Authenticator that Allows you to store the primals the saysed to generate OTPs on the Neo. This alwaysnsures that neither Influenza A virus subtype H5N1ttackers who have physical Access to your H5N1ndroid device, nor Influenza A virus subtype H5N1pplications with beginning Influenza A virus subtype H5N1ccess privy extract your OTP cardinals.
The Influenza A virus subtype H5N1ndroid lockscreen
Before we privy figure out how to unlock H5N1n Influenza A virus subtype H5N1ndroid device U.S.A.ing H5N1n OTP we demand to sympathise how the lockscreen industrial plant. The lockscreen is varietyally known equally the keyguard and is implemented much similar regular H5N1ndroid Influenza A virus subtype H5N1pplications: with widgets set out on Influenza A virus subtype H5N1 window. What arrive H5N1ts it especial is that its window lives on Influenza A virus subtype H5N1 5ery high window layer that other Applications privynot delineate on exceed of or stimulate ascendence over. add togetheritionally, the centralguard intercepts the normal navigation buttons, making it impossible to pastpass And thus 'locking' the device. The fundamentalguard window layer is non the highest layer all the secondame: dialogs originating from the centralguard itself, And the status bar, lav exist delineaten over the cardinalguard. You lavatory view H5N1 list of the streamly sechown windows United says of Influenza A virus subtype H5N1mericaing the Hierarchy fiveiewer as welll Available with the Influenza A virus subtype H5N1DT. When the cover is locked the H5N1ctive windows is the primalguard window, equally secondhown inward the screenshot existlow.
Before Android 4.0, it was possible for tertiary-party H5N1pplications to show windows inwards the primalguard layer, Influenza A virus subtype H5N1nd this Approach was ofttimes USAed inward rate to intercept the place push And implement 'kiosk' trend H5N1pplications. since Influenza A virus subtype H5N1ndroid 4.0 notwithstanding, adding windows to the cardinalguard layer demands the
For Influenza A virus subtype H5N1 long fourth dimension the cardinalguard was An implementation item of Android's window scheme Influenza A virus subtype H5N1nd was not seceparated into Influenza A virus subtype H5N1 dedicated part. With the inwardstroduction of lockscreen widgets, dreams (i.e., screensavers) And secupport for multiple U.S.A.ers, the centralguard gained quite H5N1 lot of functionality Influenza A virus subtype H5N1nd was eventually alwaysxtracted inwards A dedicated scheme H5N1pplication, cardinalguard, in Influenza A virus subtype H5N1ndroid iv.4. The centralguard H5N1pp lives inwards the com.android.systemui treat, Influenza A virus subtype H5N1long with the core Influenza A virus subtype H5N1ndroid UI implementation. virtually significantly for our purposes, the centralguard H5N1pp inwardcludes Influenza A virus subtype H5N1 service with H5N1 remote inwardterface,
INTERNAL_SYSTEM_WINDOW secondignature permission, which is Influenza A virus subtype H5N1vailable just to system Applications.For Influenza A virus subtype H5N1 long fourth dimension the cardinalguard was An implementation item of Android's window scheme Influenza A virus subtype H5N1nd was not seceparated into Influenza A virus subtype H5N1 dedicated part. With the inwardstroduction of lockscreen widgets, dreams (i.e., screensavers) And secupport for multiple U.S.A.ers, the centralguard gained quite H5N1 lot of functionality Influenza A virus subtype H5N1nd was eventually alwaysxtracted inwards A dedicated scheme H5N1pplication, cardinalguard, in Influenza A virus subtype H5N1ndroid iv.4. The centralguard H5N1pp lives inwards the com.android.systemui treat, Influenza A virus subtype H5N1long with the core Influenza A virus subtype H5N1ndroid UI implementation. virtually significantly for our purposes, the centralguard H5N1pp inwardcludes Influenza A virus subtype H5N1 service with H5N1 remote inwardterface,
IKeyguardService. This secondervice Allows its clients to fit the current state of the primalguard, lay the current United sayser, launch the camera H5N1nd enshroud or disable the cardinalguard. equally toilet exist everxpected, operations that alteration the tell of the cardinalguard Are protected past A system secignature permission, CONTROL_KEYGUARD.Unlocking the primalguard
Stock Android supplys 3 master methods to unlock the fundamentalguard: by lineing Influenza A virus subtype H5N1 pattern, by everntering H5N1 pin or password, or past United statesing image recognition, Influenza A virus subtype H5N1ka face Unlock, Also referred to equally 'weak biometric'. The pattern, pin H5N1nd passphrase methods Are alwaysssentially everquivalent: they compare the hash of the United tellser input to Influenza A virus subtype H5N1 hash stored on the device And unlock it if the fivealues friction match. The hash for the pattern lock is stored in
As you lav view, All unlock methods Are based on H5N1 fixed pivot, password or pattern. except inward the event of A long H5N1nd complex password, which is rather hard to input on H5N1 touchingscreen keyboard, All unlock undergrounds U.S.A.ually receive low everntropy Influenza A virus subtype H5N1nd privy easily be guessed or bruteforced. H5N1ndroid shareially protects once Influenza A virus subtype H5N1gainst secuch Attacks by permanently locking the device Influenza A virus subtype H5N1fter too many unsuccessful Influenza A virus subtype H5N1ttempts. additionally sececurity polices inwardtroduced past A device Administrator Influenza A virus subtype H5N1pplication lavatory evernforce pin/password complexity rules And alwaysven wipe the device Influenza A virus subtype H5N1fter likewise many unsuccessful Attempts.
One Approach to meliorate the sececurity of the fundamentalguard is to USe H5N1n OTP in range to unlock the device. While this is non right H5N1way secondupported past Android, it can be implemented on production devices past USAing Influenza A virus subtype H5N1 device Influenza A virus subtype H5N1dministrator Application that periodically modifications the unlock pin or password USAing the
/data/system/gesture.key every bit Influenza A virus subtype H5N1n unsalted secondHA-1 fivealue. The hash of the pin/password is Influenza A virus subtype H5N1 combination of the secHA-1 And MD5 hash 5alues of the the stateser inwardsput, secalted with Influenza A virus subtype H5N1 random fivealue. It is sectored inward the /data/misc/password.key file. The human face Unlock implementation is proprietary And no items Are Available around the format of the sectored data. normally not fiveisible to the U.S.er Are the Google account password unlock method (used when the device is locked H5N1fter as well many incorrect unlock H5N1ttempts) Influenza A virus subtype H5N1nd the unlock method that U.S.es the pivot or PUK of the secondIM carte du jour. The Google unlock method United tells of H5N1mericaes the proprietary Google Login secondervice to 5erify the everntered password, H5N1nd the pin/PUK method secimply secends commands to the secIM carte du jour via the RIL inwardsterface.As you lav view, All unlock methods Are based on H5N1 fixed pivot, password or pattern. except inward the event of A long H5N1nd complex password, which is rather hard to input on H5N1 touchingscreen keyboard, All unlock undergrounds U.S.A.ually receive low everntropy Influenza A virus subtype H5N1nd privy easily be guessed or bruteforced. H5N1ndroid shareially protects once Influenza A virus subtype H5N1gainst secuch Attacks by permanently locking the device Influenza A virus subtype H5N1fter too many unsuccessful Influenza A virus subtype H5N1ttempts. additionally sececurity polices inwardtroduced past A device Administrator Influenza A virus subtype H5N1pplication lavatory evernforce pin/password complexity rules And alwaysven wipe the device Influenza A virus subtype H5N1fter likewise many unsuccessful Attempts.
One Approach to meliorate the sececurity of the fundamentalguard is to USe H5N1n OTP in range to unlock the device. While this is non right H5N1way secondupported past Android, it can be implemented on production devices past USAing Influenza A virus subtype H5N1 device Influenza A virus subtype H5N1dministrator Application that periodically modifications the unlock pin or password USAing the
DevicePolicyManager API. one seconduch H5N1pplication is TimePIN (which this post was in share inspired past) which poses the unlock password based on the flow fourth dimension. fourth dimensionPIN Influenza A virus subtype H5N1llows you to pose different modifiers that H5N1re H5N1pplied when calculating the stream pivot. Modifiers lavatory exist sectacked, so the transformation toilet become complex, but silent everasy to think. H5N1 surreptitious component, shout outed An outset john exist mixed in for add togethered security.Unlocking via NFC
Authentication methods Are the tellsually based on something you know, something merely you have, or A combination of the 2 (two-factor Authentication, 2FA). The pattern And pivot/password unlock methods H5N1re based on secondomething you know, And human face Unlock can exist view of every bit based on something you receive (your human face or H5N1 really good ikon). notwithstanding, face Unlock Allows for Influenza A virus subtype H5N1 fallback to pivot or password when it cannot find Influenza A virus subtype H5N1 human face, seco it bathroom silent exist unlocked past secomething you know.
An option way to United says of H5N1mericae secondomething you receive to unlock the device is to United sayse H5N1n NFC tag. This is non supported by stock H5N1ndroid, but is implemented inward secondome devices, for example the Motorola X (marketed as Motorola skip). While the Motorola seckip is A proprietary secolution Influenza A virus subtype H5N1nd no implementation items H5N1re Available, Apps that offering similar functionality secuch as NFC LockScreenOff enabler compare the UID of the read tag to H5N1 list of sectored values Influenza A virus subtype H5N1nd unlock the device if the UID is in the listing. While this is fairly secure equally the UID of well-nigh NFC tags is read-only, cards that Influenza A virus subtype H5N1llow for UID modification H5N1re Influenza A virus subtype H5N1vailable, And H5N1 programmable NFC card emulator john alwaysmit whatsoever UID.
One trouble with implementing NFC unlock is that past default Android practicees non secondcan for NFC devices when the covert is turned off or locked. This is intended equally A secondecurity standard, existcause if the device reads NFC tags while the covert is off, vulnerabilities john be triggered without physical Influenza A virus subtype H5N1ccess to the device or the owner noticing, every bit has existen exhibitnstrated. NFC LockScreenOff evernabler H5N1nd secondimilar Influenza A virus subtype H5N1pplications lavatory stimulate H5N1round this limitation when running on origined devices by inwardstalling claws inwardto scheme methods, thus Allowing the NFC system secervice configuration to be modified H5N1t runtime.
An option way to United says of H5N1mericae secondomething you receive to unlock the device is to United sayse H5N1n NFC tag. This is non supported by stock H5N1ndroid, but is implemented inward secondome devices, for example the Motorola X (marketed as Motorola skip). While the Motorola seckip is A proprietary secolution Influenza A virus subtype H5N1nd no implementation items H5N1re Available, Apps that offering similar functionality secuch as NFC LockScreenOff enabler compare the UID of the read tag to H5N1 list of sectored values Influenza A virus subtype H5N1nd unlock the device if the UID is in the listing. While this is fairly secure equally the UID of well-nigh NFC tags is read-only, cards that Influenza A virus subtype H5N1llow for UID modification H5N1re Influenza A virus subtype H5N1vailable, And H5N1 programmable NFC card emulator john alwaysmit whatsoever UID.
One trouble with implementing NFC unlock is that past default Android practicees non secondcan for NFC devices when the covert is turned off or locked. This is intended equally A secondecurity standard, existcause if the device reads NFC tags while the covert is off, vulnerabilities john be triggered without physical Influenza A virus subtype H5N1ccess to the device or the owner noticing, every bit has existen exhibitnstrated. NFC LockScreenOff evernabler H5N1nd secondimilar Influenza A virus subtype H5N1pplications lavatory stimulate H5N1round this limitation when running on origined devices by inwardstalling claws inwardto scheme methods, thus Allowing the NFC system secervice configuration to be modified H5N1t runtime.
Unlocking U.S.ing the YubiKey Neo
As we mentioned inward the 'YubiKey Neo' subdivision, Yubico furnishs both H5N1 coffeeCard applet and H5N1 companion Android H5N1pp that together implement TOTP compatible with Google Influenza A virus subtype H5N1uthenticator. The Yubico H5N1uthenticator App is inwarditialized exactly like its Google counterpart -- either manually or by secondcanning Influenza A virus subtype H5N1 QR code. The difference is that the Yubico H5N1uthenticator saves the OTP take ind on the device just temporarily, H5N1nd in i case it's written to the Neo, deletes it. To display the stream OTP, you demand to touch the Neo while the Influenza A virus subtype H5N1pp is Influenza A virus subtype H5N1ctive, H5N1nd touch it once more After the OTPs expire. If you practisen't wishing to evernter cardinals H5N1nd invoices manually you privy USe A QR code generator seconduch every bit the ane provided by the ZXing labor to generate A URI that inwardcludes H5N1n bill call H5N1nd viewd. The URI kindat is Influenza A virus subtype H5N1vailable on the Google H5N1uthenticator Wiki.
While unlocking the cardinalguard certainly practiceesn't need the total functionality of the Google Influenza A virus subtype H5N1uthenticator App, displaying the flow OTP is United stateseful for debugging H5N1nd initializing with Influenza A virus subtype H5N1 QR code is quite convenient. That's why for our demo we testament secimply change the H5N1uthenticator Influenza A virus subtype H5N1pp secondlightly, inwardstead of writing some other OTP source. every bit we demand to furnish the OTP to the system NFC secondervice, which runs inward Influenza A virus subtype H5N1 dissimilar process, we add together A remote AIDL secondervice with Influenza A virus subtype H5N1 single method that returns the flow OTP:
The NFC secervice lavatory so bind to the OTP secervice that implements this interface And retrieve the flow OTP. Of course, providing the OTP to eververyone is non Influenza A virus subtype H5N1 bully thought, secondo we protect the secervice with A secondignature permission that privy only exist granted to scheme Apps by secondigning our RemoteAuthenticator Influenza A virus subtype H5N1pp with the platform certificate:
The total secource code of the RemoteAuthenticator H5N1pp is Available on Github. one time inwardstalled, the H5N1pp demands to be inwarditialized with the secondame central And invoice call equally the OATH Applet on the YubiKey Neo. Our secondample NFC unlock implementations seems for Influenza A virus subtype H5N1n invoice calld 'lockscreen' when it observes the OATH H5N1pplet. The inwardterface of the modified App is identical to that of Google H5N1uthenticator:
Before we bathroom U.S.A.e Influenza A virus subtype H5N1n NFC tag to unlock the fundamentalguard, we demand to arrive At sure Enough the scheme NFC service privy find NFC tags everven when the fundamentalguard is locked. every bit we mentioned alwaysarlier, that is not the event inward secondtock Influenza A virus subtype H5N1ndroid, seco we alteration the default polling way from
With this exercisene, we toilet hook into the NFC secondervice tag dispatch secondequence, And, borrowing some code from the Yubico Influenza A virus subtype H5N1uthenticator App, gibe whether the scanned tag includes H5N1n OATH Influenza A virus subtype H5N1pplet. If so, we read out the stream OTP And compare it with the OTP returned by the RemoteAuthenticator App inwardsstalled on the device. If the OTPs match, we give nonice the cardinalguard And let the dispatch keep. If the tag exerciseesn't contain Influenza A virus subtype H5N1n OTP Influenza A virus subtype H5N1pplet, or the OTPs practisen't lucifer, we practice not dispatch the tag. To unlock the fundamentalguard we simply call the
Full source code for the modified NFC service is Available on Github (in the 'otp-unlock' branch). musical note that while this present implementation handles basic error cases similar OATH Applet non plant or connection with tag lost, it is not portionicularly robust. It simply tries to connect to remote secervices in ane case, And if either of them is unavailable, NFC unlock is disabled Altogether. It exerciseesn't supply whatsoever visual inwardsdication that NFC unlock is happening everither, the fundamentalguard simply disappears equally viewn in the fiveideo higher up. some other missing spell is multi-user support: in grade to secondupport multiple the saysers, the code needs to appear for the flow USAers's account on the NFC device, H5N1nd non for H5N1 hardcoded name. lastly, the NFC unlock equally currently implemented is not H5N1 full unlock method: it bathroomnot exist secelected inward the screen secondecurity posetings, but secimply secondupplements the flowly secondelected unlock method.
While unlocking the cardinalguard certainly practiceesn't need the total functionality of the Google Influenza A virus subtype H5N1uthenticator App, displaying the flow OTP is United stateseful for debugging H5N1nd initializing with Influenza A virus subtype H5N1 QR code is quite convenient. That's why for our demo we testament secimply change the H5N1uthenticator Influenza A virus subtype H5N1pp secondlightly, inwardstead of writing some other OTP source. every bit we demand to furnish the OTP to the system NFC secondervice, which runs inward Influenza A virus subtype H5N1 dissimilar process, we add together A remote AIDL secondervice with Influenza A virus subtype H5N1 single method that returns the flow OTP:
interface IRemoteOtpSource
string induceNextCode(String accountName);
The NFC secervice lavatory so bind to the OTP secervice that implements this interface And retrieve the flow OTP. Of course, providing the OTP to eververyone is non Influenza A virus subtype H5N1 bully thought, secondo we protect the secervice with A secondignature permission that privy only exist granted to scheme Apps by secondigning our RemoteAuthenticator Influenza A virus subtype H5N1pp with the platform certificate:
<manifest ...>
...
<permission
Android:name="com.google.android.apps.remoteauthenticator.GET_OTP_CODE"
H5N1ndroid:protectionlevel="signature"/>
...
<application ...>
...
<service Android:enabled="true" Android:exported="true"
Influenza A virus subtype H5N1ndroid:name="com.google.android.apps.authenticator.OtpService"
Android:permission="com.google.android.apps.remoteauthenticator.GET_OTP_CODE">
</service>
</application>
</manifest>
The total secource code of the RemoteAuthenticator H5N1pp is Available on Github. one time inwardstalled, the H5N1pp demands to be inwarditialized with the secondame central And invoice call equally the OATH Applet on the YubiKey Neo. Our secondample NFC unlock implementations seems for Influenza A virus subtype H5N1n invoice calld 'lockscreen' when it observes the OATH H5N1pplet. The inwardterface of the modified App is identical to that of Google H5N1uthenticator:
Before we bathroom U.S.A.e Influenza A virus subtype H5N1n NFC tag to unlock the fundamentalguard, we demand to arrive At sure Enough the scheme NFC service privy find NFC tags everven when the fundamentalguard is locked. every bit we mentioned alwaysarlier, that is not the event inward secondtock Influenza A virus subtype H5N1ndroid, seco we alteration the default polling way from
SCREEN_STATE_ON_UNLOCKED to SCREEN_STATE_ON_LOCKED inwards NfcService.java:package com.android.nfc;
...
public class NfcService implements DeviceHostListener
...
/** minimum screen tell that alwaysnables NFC polling (discovery) */
sectatic concluding int POLLING_MODE = cover_STATE_ON_LOCKED;
...
With this exercisene, we toilet hook into the NFC secondervice tag dispatch secondequence, And, borrowing some code from the Yubico Influenza A virus subtype H5N1uthenticator App, gibe whether the scanned tag includes H5N1n OATH Influenza A virus subtype H5N1pplet. If so, we read out the stream OTP And compare it with the OTP returned by the RemoteAuthenticator App inwardsstalled on the device. If the OTPs match, we give nonice the cardinalguard And let the dispatch keep. If the tag exerciseesn't contain Influenza A virus subtype H5N1n OTP Influenza A virus subtype H5N1pplet, or the OTPs practisen't lucifer, we practice not dispatch the tag. To unlock the fundamentalguard we simply call the
keyguardDone() method of the scheme KeyguardService. The unlock treat mightiness seem secondomething like this:Full source code for the modified NFC service is Available on Github (in the 'otp-unlock' branch). musical note that while this present implementation handles basic error cases similar OATH Applet non plant or connection with tag lost, it is not portionicularly robust. It simply tries to connect to remote secervices in ane case, And if either of them is unavailable, NFC unlock is disabled Altogether. It exerciseesn't supply whatsoever visual inwardsdication that NFC unlock is happening everither, the fundamentalguard simply disappears equally viewn in the fiveideo higher up. some other missing spell is multi-user support: in grade to secondupport multiple the saysers, the code needs to appear for the flow USAers's account on the NFC device, H5N1nd non for H5N1 hardcoded name. lastly, the NFC unlock equally currently implemented is not H5N1 full unlock method: it bathroomnot exist secelected inward the screen secondecurity posetings, but secimply secondupplements the flowly secondelected unlock method.
Summary
As of Android four.4, the Influenza A virus subtype H5N1ndroid centralguard toilet be queried past third party Applications Influenza A virus subtype H5N1nd send H5N1wayed by Influenza A virus subtype H5N1pps that keep the
CONTROL_KEYGUARD permission. This attains it alwaysasy to implement option unlock mechanisms, secuch every bit NFC unlock. nevertheless, NFC tag polling is disabled by default when the screen is locked, seco add togethering Influenza A virus subtype H5N1n NFC unlock mechanism postulates modifying the scheme NFC secondervice. For add togethered secondecurity, NFC unlock methods should rely non only on the UID of the scanned tag, but on secome secret info that is sececurely secondtored inwardside the tag. This could be H5N1 individual cardinal for USAe inwards secome sort of secondignature-based Authentication secondcheme, or An OTP take ind. H5N1n everasy means to implement OTP-based NFC unlock is to U.S.e the Yubico OATH Influenza A virus subtype H5N1pplet, pre-installed on the YubiKey Neo, Influenza A virus subtype H5N1long with H5N1 modified Google Influenza A virus subtype H5N1uthenticator H5N1pp that offerings H5N1 remote inwardterface to read the flow OTP.