e- passports

Erik Poll

Digital Security GroupRadboud University Nijmegen

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overview

• e-passports• functionality and security mechanisms• problems, so far• future

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e-passports

• e-passport contains RFID chip / contactless smartcard – in Dutch passports, a Java Card

• chip stores digitally signed information:– initially just facial images (photos)– soon also fingerprints– later maybe iris

• aka biometric passport or MRTD with ICC/chip

• introduction pushed by US in the wake of 9/11– to solve what problem??

• international standard by ICAO (International Civil Aviation Organization, branch of United Nations) e-passport logo

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Protocols & standards

ISO 14443 • defines physical communication for RFIDsISO 7816 • originally developed for contact smartcards• defines standard APDU commands & responses,ICAO  standard for e-passports• defines specific IS0 7816 commands and responses for passportsadditional EU standards• standardise optional parts of ICAO specs & fix timeline• additional advanced secuity mechanisms on top of ICAO

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National id-cards & terminology

• Nederlandse Identiteitskaart (NIK) conforms to the same ICAO specification

NB possible confusion• eNIK is a future extension of NIK, with digital signature capability• MRTD = Machine-Readable Travel Document just has Machine (OCR) Readable Zone, the MRZ, but need not contain a chip ie. e-passport = MRTD + chip

MRZ

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European Electronic Passport

• Council decision of 13 December 2004 The facial image will be required at the latest 18 months,

– the fingerprints will be required mandatory at the latest 36 months

after the date of adoption of technical specifications necessary for the implementation of the Regulation

• Facial images: deadline 28 August 2006• Fingerprints: deadline 28 June 2009

– protected by additional security mechanism, extended access control

• Participants: all members except UK, IRL, NOR

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e-passports & authentication

• authentication of data• authentication of the chip• authentication of the terminal

– why? how?• authentication of the passport holder

– how?• passport data: age, height, gender,...• facial image, fingerprint, iris• signature

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Biometrics to authentication passport holder

• Facial image (DG2, ISO 19794-5)– JPEG or JPEG2000 image– Basic, Full Frontal, Token Image– Feature points (e.g. eyes)

• Fingerprint (DG3, ISO 19794-1)– Uncompressed, WSQ, PNG, JPEG or JPEG2000– How to indicate the fingerprint cannot be enrolled (no DG3,

empty DG3, no template), how to store 2 fingerprints (2 images, 2 templates)

• Iris image (DG4, ISO 19794-6)• NB one would prefer not to store the raw biometrics, but

some (hash of) derived info. Why? How?

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Security mechanisms

• Passive Authentication (PA)– digital signature on passport data on chip

• Basic Authentication Control (BAC)– access control to chip, to prevent

unauthorised access & eavesdropping• Active Authentication (AA)

– chip authentication• ie prevent cloning

• Extended Access Control (EAC)– chip and terminal authentication

ICAOmandatory

ICAO optional,EU mandatory

EU only, mandatory for 'advanced' biometrics,

ie fingerprint & iris

ICAO optional

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Passive Authentication

• passport chip consists of 16 data groups (DGs) – DG1 MRZ– DG2 face– DG3 finger– DG4 iris– ...– DG15 Active Authentication– ...

and a security object SO, – signed hash values of the data groups

• To check the signatures, terminal needs country signing certificates

• Passive Authentication mandatory on all e-passports

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Basic Access Control (BAC)

• Contactless interface is both advantage and disadvantage• BAC allows to read the data only after reader authentication:

– reader proves knowledge of the MRZ of the passport• The authentication key is derived from document nr, date of

birth, date of expiry• BAC is ICAO optional (recommended) feature, in EU

mandatory• Interoperability issue

– How to find out the passport is BAC-protected? → try & you find out

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Basic Access Control (BAC)

protects against unauthorised access and eavesdropping

receive additional info

optically read MRZ

send MRZ

MachineReadableZone

encrypted

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BAC details

• Kseed derived from MRZ

• 3DES keys KENC and KMAC derived from Kseed

– KENC = first 8 bytes of HASH(KNseed , 0x 00 00 00 01)

– KMAC = first 8 bytes of HASH(KNseed , 0x 00 00 00 02)

• Terminal (IFD) and card (ICC) both generate – 8 byte randoms RNDIFD , RNDICC

– 16 byte randoms KIFD , KICC

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BAC details

• IFD ICC : GET_CHALLENGE→

• ICC IFD : RND→ ICC

• IFD ICC : MUTUAL_AUTHENTICATE( E→ IFD || MIFD)

with S = RNDIFD|| RNDICC|| KIFD

EIFD= Enc (S,KENC), MIFD= MAC (EIFD,KENC)

• ICC checks MAC and computes S, and hence RNDIFDand KIFD

• ICC IFD : E→ ICC || MICC

with R = RNDIFD|| RNDICC || KICC

EICC = Enc (R,KENC), MICC = Enc (EICC ,KMAC)

• Both calculate new Kseed = KIFD KICC

and derive SKENC and SKMAC for secure messaging

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Alternative: Faraday Cage

• protects against unauthorised access, but not eavesdropping– used in US passports, initially instead of BAC

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Active Authentication (AA)

protects against passport cloning (which BAC doesn't)ie authentication of the passport chip

public key, signed by government (DG15)

send challenge

prove knowledge ofcorresponding private key

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similarity with EMV

• ICAO passive and active authentication similar to EMV static and dynamic data authentication, resp.

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possible drawback of AA: challenge semantics

• passport chip that supports AA will sign any challenge • terminal could choose challenge c with some semantics

– eg. c = Sign(SKterminal, IDpassport ++ date ++ location)– card replies Sign(SKpassport, c)

• can be useful - eg unfakeable log of entry to the country – but do we want it?– NB AA is – and should of course be - protected by BAC

• This can be prevented by not using a challenge signed by an asymmetric key, but using assymmetric crypto to establish a shared secret symmetric key that is used for MACs

• as in EAC

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Different ways to do authentication

1. Shared key (symmetric or assymmetric, possibly diversified)• A -> B : Encrypt(K, random || idA)• B -> A : Encrypt(K, random || idB)

1. Cipher-based authentication using public keys– A chooses random key K– A -> B : Encrypt(PKB, K)– B -> A : MAC(K, idA || idB)

1. Signature-based authentication– A -> B : challenge– B -> A : Encrypt(SKB, challenge || idA || idB)

Challenge semantics only possible with 3, becausesignature in 3 requires assym. SKB key that only B has

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Extended Access Control (EAC)

includes authentication of terminal by passport• why would we want this?

– leaking privacy-sensitive information, eg at hotel check-in– esp fingerprint & iris

• how would we do this?– some terminal certificate– ISO 7816 Card Verifiable (CV) certificates used rather than

X.509 public key certificates. • what are problems with this?

– certificate revocation hard to realise• how do you revoke a terminal certificate on all passports?

– certificates for short periods• passport does not have time to check certificate expiry

– chip can only record date of last transaction

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Extended Access Control (EAC)

Two phases

• Chip Authentication– replaces AA– starts Secure Messaging (SM) with stronger keys

• Terminal Authentication– uses traditional challenge-response:– terminal sends certificate chain to chip– chip sends challenge– terminal replies with signed challenge

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Extended Access Control

Chip Authentication• chip -> terminal: PKpassport

• terminal chooses ephemeral DH key pair (SKtemp, PKtemp)• terminal -> chip: PKtemp

• chip and terminal compute shared symmetric key K– K = KA(SKpassport,PKtemp)=KA(SKtemp,PKpassport)

with derived session keys for encryption Kenc and MAC Kmac

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• Having the chip authenticate terminal opens up further possibilities, eg – updating data on chip– uploading visa & travel records

but so far the passport does not support any writing of data after personalisation

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DG Content read/write mandatory / optional

acccess control

DG1 MRZ R m BAC

DG2 Face R m BAC

DG3 Finger R o BAC+EAC

DG4 Iris R o BAC+EAC

.. R

DG14 SecurityInfo* R o BAC

DG15 AA public key R o BAC

DG16 R

SO Security Object R m BAC

*ANS.1 data structure indicating support for Chip and Terminal Authentication, and defining. Chip Authentication Public Key

problems with passports, so far...

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passive vs active attacks on RFID

passive attacks• eavesdropping on

communication between passport & reader

• possible from several meters

active attacks• unauthorised access to

passport without owner's knowledge

• possible up to 25 cm– activating RFID tag

requires powerful field!

• aka virtual pickpocketing• variant: relay attack

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Problem with BAC: low entropy in MRZ

• MRZ key based on passport number, expiry and birth dates• passport numbers typically issued in sequence, so low entropy,

and strongly correlated with expiry date– 3DES max 112bit, BAC max 56/74bit, in practice 30-50

• off-line brute force attack on eavesdropped traffic is possible [Marc Witteman & Harko Robroch, 2006]

• first discovered for Dutch passport, but other countries had the same problem

• solutions?– changing the key derivation procedure rejected by ICAO for

compatibility issues– not handing out passport no's in sequence caused organisational

/operational problems

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Problems with Belgian passports

• First generation of Belgian passports (2004-2006) did not support BAC– so MRZ (DG1) skimmable in fraction of a second, all

passport info in about 10 secs• These passports provide info not required by ICAO, incl

– place of birth– digital version of signature

• Also, same problem with low entropy of MRZ as Dutch passports– moreover, different ranges of passport no's reserved for

Flemish and Walloon passports

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Problem with ISO 14443: fixed UIDs

• Normal ISO 14443 tags sent a fixed UID as part of the anti-collision protocol

• This would allow tracking of individual passports

• Producing random UID requires non-standard hardware• Some countries still used fixed UIDs

• First generation of Dutch passports does not have truly random UIDs, as 2 bits in the random UIDs are always the same...

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Problems with terminals

• Lukas Greenwald reported some terminals crashing with a buffer overflow on malformed JPEG– missing input validation, as usual...

• Jeroen van Beek (UvA) reported some terminals failing to check digital signatures correctly– ICAO specs somewhat tricky

• eg will terminal spot a clone of a passport that says it does not support AA?

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• bla

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Problem: determining passport origin

• Error messages of the card reveal manufacturer

– ie provide fingerprint

• BSc thesis by Henning Richter here in Nijmegen

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Errors can leak information

An Error Has Occurred.

Error Message:

System.Data.OleDb.OleDbException: Syntax error

(missing operator) in query expression

'username ''' and password = 'g''.

System.Data.OleDb.OleDbCommand.ExecuteCommandTextErrorHandling (Int32 hr) at

System.Data.OleDb.OleDbCommand.ExecuteCommandTextForSingleResult (tagDBPARAMS dbParams, Object& executeResult) at

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Fingerprinting passports

• All e-passports react the same to correct protocol runs....

• but what about incorrect ones? Eg – commands out of sequence

• eg B0 (READ BINARY) before completing BAC– commands not in the ICAO specs at all

• eg 44 (REHABILITATE CHV)– commands with silly parameters

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Example commands & responses

Commands sent to card include 1 instruction byte, eg• A4 SELECT FILE • B0 READ BINARY • 84 GET CHALLENGE• 82 EXTERNAL AUTHENTICATE• ...Responses from card include 2 bytes status word, eg• 9000 No error• 6D00 Instruction not supported• 6986 Command Not Allowed • 6700 Wrong Length• ...Defined in ISO7816, re-used in ICAO specs

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Example responses to B0 instruction

response

(status word)

meaning

Belgian 6986 not allowedDutch 6982 security status not satisfied

French 6F00 no precise diagnosisItalian 6D00 not supportedGerman 6700 wrong length

255 other instructions to try, and we can try different parameters ...

B0 means "read binary", and is only allowed after BAC

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Fingerprinting passports

• Response to strange inputs provides unique fingerprint for ten nationalities originally tested – Australian, Belgian, Dutch, French, German,

Greek, Italian, Polish, Spanish, Swedish

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Detecting & distinguishing passports

• 4 commands suffices to distinguish between the 10 nationalities we tested– instruction byte 82 identifies Australian, Belgian, French,

and Greek – A4 identifies Dutch and Italian – 88 identifies Polish and Swedish – 82 with different parameter identifies German and

Spanish • Code to do this is very simple & very fast

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Fingerprinting passports

• This fingerprint depends on implementation choices in the software– upgrading hardware would not affect this

• If countries use the same implementation (ie. get passport from same supplier), the fingerprints would be identical– Indeed, Dutch, Irish, Finnish and Slovak

passports give identical responses

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The small print in the specs

"A MRTD chip that supports Basic Access Control must respond to unauthenticated read attempts (including selection of (protected) field in the LDS) with ‘Security Status not satisfied’ (6982)"

[PKI for machine readable travel documents offering ICC read-only access, version 1.1. Technical report, ICAO, Oct 2004.]

but what constitutes a "read attempt"?

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More fingerprinting possibilities

• Our approach fingerprints passport application– so upgrading hardware or OS won't affect

fingerprint• Fingerprinting may be possible at other levels, eg

– OS– hardware

smartcard hardware

passport application

operating system

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More fingerprinting possibilities

• ATS (Answer To Select)– sent by RFID on activation to indicate eg

supported data rate, but also operating system version (in "historical bytes")

– New Zealand passport sends "JCOP41V22", so it's an IBM/NXP JCOP card, version 4.1, running Java Card 2.2

• Other OS behaviour– eg Dutch passport recognisable as Java Card,

as it supports Global Platform • Physical characteristics

– power consumption, response times, ....

Remember this?

>telnet hera.cs.kun.nlTrying 131.174.142.11Connected to heraRed Hat Linux 2.4.18login:

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Countermeasures to fingerprinting

• better specs– clearly prescribing standard error responses– or, all countries could simply use a common open

source implementation• eg our Java Card implemententation

[http://jmrtd.sourceforge.net]– but infeasible to do now, once specs & implementations

exist

• metal shielding in passport cover (Faraday cage)– defence-in-depth

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Abuse cases for fingerprinting?

• Passport bomb triggered by a specific nationality• Selection of potential victims by passport thieves

Fortunately, limited range for active attacks (25cm, maybe a bit more) reduces any serious threat

Also, there may be easier ways to detect nationality...

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Other risk: transferability

• Downside using digital signatures: someone reading the passport info can store it, or pass it on to a third party, with the digital signatures

– Eg if country B can read fingerprint info of passport from country A, this info can be passed on to country C, who can check authenticity of all info

• Instead of sending signed data, the chip could– after being authenticated, provide unsigned data,

• This data can be trusted if we have authenticated the chip, but trust cannot be transferred or stored

– use some protocols for non-tranferable proofs

Conclusions

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Questions

• What is the problem solved/security improved by RFIDs in passports?

• Does it outweight the new risks?

• Potential problem/opportunity: function creep?

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On-line authentication

• Passive authentication only proves such a person/passport exists (not that it is yours etc.)

• Active Authentication proves you have physical access to passport:

AA can be used to login to computer or website like other smartcards– Martijn Oostdijk et al. (Novay) implemented a

demonstrator using AA to log on, using Windows CardSpace (aka Info Card)

– [open source at http://jmrtd.org/authep]

• Remote biometric authentication is of course not secure

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Other existing & future e-ID initiatives

• US Passport Cards and Enhanced Driver License (EDL) include a simple RFID tag, which just broadcasts a unique UID– readable at larger distances than ISO14443 passport tags

• ISO18013 standard for e-driving license– very similar to ICAO specs– first implementation done by Wojtek

• Additional functionality for e-id cards: digital signatures– already in eg. Belgian e-id, foreseen for Dutch e-NIK– eg for citizen access to Electronic Patient Dossier (EDP)?– EU guidelines for digital signatures in place

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Questions?

• Code for passport terminal and passport available at http://jmrtd.sourceforge.net