Part 3: Communication Security Basics

1
Part 3 Communication Security Basics

• Chapter b Security features of the Wireless
  Application Protocol (WAP)

2
Contents

• What is WAP?
• WAP I and WAP II
• WAP-PKI
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

3
Contents

• What is WAP?
• WAP I and WAP II
• WAP-PKI
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

4
Example Ask for train connections
5
Contents

• What is WAP?
• WAP I and WAP II
• WAP-PKI
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

6
Web-Modell
7
WAP I model Translator WAP - WEB
Gateway
Client
Server
encoded req.
req.
Encode Decode
WAEUserAgent
cgi scriptsetc.
encoded resp.
resp.
WAP I
WEB
8
WAP I protocol stack
WAP
WEB
Application (WAE)
Application
Session (WSP)
HTTP
Transaction (WTP)
TCP
Security (WTLS)
Security (TLS)
Transport (WDP)
IP/UDP
Medium GSM, CDMA, UMTS ...
Medium ...
9
WAP II Model WAP talks WEB
optional
Server
req.
cgi scriptsetc.
Client
resp.
WAEUserAgent
Push
Push
WEB
10
Example for a WAP II configuration TCP und
HTTP
WEB
WAP
Proxy
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Example for WAP II configuration TLS Tunneling
WEB
WAP
Proxy
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Contents

• What is WAP?
• WAP I and WAP II
• WAP-PKI
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

13
WAP PKI

• PKI portal provides PKI services
• PKI portal connected via gateway or direct with
  mobile phone
• 2 keys
• authentication
• signing
• Device certificates possible
• New certificate format WTLS certificate
• advantage compact
• Client certificates often not stored in client

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Root keys

• Root key validation
• Signature Signed by reliable party
• or
• Hash User must type 30 (!) digits

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Certificates for servers

• Long time certificates (as for WEB servers)
• Server generates PKCS10 request
• CA sends certificate

• 2. Short time certificates (keine CRLs)
• Client subscribes at CA (one-time)
• Gets a new certificate (e.g.) every day

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Certificates for clients

• Authentication certificate
• Client sends cert. request using WTLS to PKI
  Portal
• Proof of Possession (POP) by WTLS
• Signaturcertificate
• Client signes text for POP
• Delivery
• certificate
• LDAP-URL
• HTTP-URL

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Contents

• What is WAP?
• WAP I and WAP II
• WAP-PKI
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

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Problem Variables in WML

• WML allows setting and writing of
  variables
• Problem Other decks can read this variable

ltwmlgt ltcardgt ... ltsetvar
nameshopping_cart value31415gt ltdo
"typeaccept"gt ltgo href"http//wap.versand.
de/shopping_cart"gt lt/dogt lt/cardgt lt/wmlgt
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Problem Variables in WML (cont.)

• Solutions access element
• But No cryptographic authentication of the
  permitted decks
• Variables should not be used for passwords

20
Digitale signature within WMLScript
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Contents

• What is WAP?
• WAP I and WAP II
• WAP-PKI
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

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Design goals of WTLS

• Authentication of communication partner
• Confidentiality of communication data
• Integrity and authenticity of communication data
• Interoperability
• Efficiency
• Extensibility
• But No non-repudiation

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Architecture of WTLS
PSE
Data
Handshake
Change Cipher Spec.
ApplicationData
Alert
WTLS
Record
WDP
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WTLS in principle
Errare humanum est.
WTLS record protokol
Compression of Errare ...
eTiasd
Cryptogram of Errare ...Encrypted by a
symmetric algorithm and protected by a MAC
Cryptogram of Errare ...
aBziEa
xdsiWn
WDP-Protokoll
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Architecture of WTLS (repitition)
PSE
Data
?
Handshake
Change Cipher Spec.
ApplicationData
Alert
WTLS
?
Record
WDP
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6 symmetric keys
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Handshake protocol, option 1 Server-only
authentication
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No non-repudiation
3
Sorry, I can not decide this!
2
I did not receive any messageby Alice.The log
file has been fakedby Alice!
1
I have canceled thecontract for my flat3 months
ago.

• Reason The record protocol is based on symmetric
  cryptography

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TLS vs. WTLS
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Contents

• What is WAP?
• WAP I and WAP II
• WAP-PKI
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

31
Contents

• What is WAP?
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

32
Wireless Identity Module (WIM)

• Tamper proof hardware for PSE
• Contains keys
• Stores Master Secrets
• Stores Shared Secret (opt.) for WTLS
• Signes data
• Verifies data
• PKCS15 format
• Can be used outside of WAP
• Can be placed on SIM

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WIM function groups

• Management
• Verification
• Data access
• Cryptography
• Exceptions

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WIM function groups

• Management
• Verification
• Data access
• Cryptography
• Exceptions

• Open Service
• Close Service

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WIM function groups

• Management
• Verification
• Data access
• Cryptography
• Exceptions

• Perform Verification
• Disable Ver. Req.
• Enable Ver. Req.
• Change Reference Data
• Unblock Reference Data

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WIM function groups

• Management
• Verification
• Data access
• Cryptography
• Exceptions

• Open File
• Close File
• Read Binary
• Update Binary

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WIM function groups

• Management
• Verification
• Data access
• Cryptography
• Exceptions

• Compute Dig. Sig.
• Verify Dig. Sig.
• Get Random
• Key Transport
• Key Agreement
• Derive Master Secret
• Phash
• Decipher

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WIM function groups

• Management
• Verification
• Data access
• Cryptography
• Exceptions

• Exception

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Contents

• What is WAP?
• WAP I and WAP II
• WAP-PKI
• Application layer WML WMLScript Crypto Lib
• Transport layer WTLS
• Hardware WIM
• Problems

40
Problems

• WAP I gateway must translate between TLS and WTLS
  ? clear data phase required
• Bugs in implementation of the gateway can
  generate problems (e.g. identification via IP
  numbers)
• Mobile phone must be configured carefully
• Verification of reliable certificates is
  cumbersome

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Summary

• WAP I Efficient
• WAP II Direct usage of WEB protocols,
  configureable
• Digital signatures on the application layer
• WTLS is considered secure
• WIM based on smart card is a well known concept
• Display of mobile phone too small
• Usage cumbersome
• WAP II Complex. Is it worth this?

42
References (www.wapforum.org)

• WMLScript Crypto API Library Specification
• WAP-161-WMLScriptCrypto-20010620-a
• Wireless Identity Module Specification
• WAP-260-WIM-20010712-a
• Wireless Transport Layer Security Specification
• WAP-261-WTLS-20010406-a
• WAP Certificate profile Specification
• WAP-211-WAPCert-20010522-a
• WAP Public Key Infrastructure Specification
• WAP-217-WPKI-20010424-a
• WAP TLS Profile and Tunneling Specification
• WAP-219-TLS-20010411-a
• End-to-end Transport Layer Security
  Specification