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1 Wireless Security 4 – Wireless Public Key Infrastructure Chapter 15 of Wireless Maximum Security by Peikari, C. and Fogie, S.

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Presentation on theme: "1 Wireless Security 4 – Wireless Public Key Infrastructure Chapter 15 of Wireless Maximum Security by Peikari, C. and Fogie, S."— Presentation transcript:

1 1 Wireless Security 4 – Wireless Public Key Infrastructure Chapter 15 of Wireless Maximum Security by Peikari, C. and Fogie, S.

2 2 WPKI Public key cryptography Digital signatures Certificate authorities Wireless PKI implementation Transaction confirmation Integrity of user identities 3 rd Party services WAP PKI

3 3 Public key cryptography RSA 非對稱密鑰密碼演算法  based on the difficulty 艱難 of factoring 因子分解  larger numbers  Used in digital signature 數位簽署 and key exchange 交換 operations 操作 DSA  Based on the difficulty of calculating discrete 離 散 logarithms  Used in digital signature Diffie-Hellman  Based on the difficulty of calculating discrete logarithms in the finite field  Used for key exchange only

4 4 Digital signatures 數位簽署 To tackle 處理 spoofing 電子欺騙 or tampering 損害 One-way Hash 散列 Algorithms 演算法  A hash utilizes 1-way (irreversible 不能倒逆的 ) mathematical function (a hash algorithm) to transform 變換 data into a fixed-length unique digest, known as the hash value.  MD5 produces 128-bit hash value  SHA-1 produces 160-bit hash value (more secure)

5 5 Certificate 証書 authorities 權威 Is any entity 實體 or service that issues 發料 certificates CAs act as guarantors of the binding 連結 between the public key and the owner’s identity information and is contained in the certificates it issues. Companies will outsource this service to a commercial CA such as VeriSign. A certificate is a public key that is digitally signed and packaged 封裝 for use in a PKI.

6 6 Certificate authorities X.509 v3 Certificate Standard specifies 設定 the certificate format 格式 for information about the person or entity to which the certificate is issued, information about the certificate, plus optional information about CA issuing the certificate. Certificate format: version, serial no., signature, issuer, validity 驗證, subject, subject’s PK information, Issuer unique identifier, extensions 延伸

7 7 PKI Weakness 弱點 Stop the user to use Certificate Revocation 廢止, 取消, 撤回 List 50 ways to defeat PKI – by Fred Cohen  Basic social engineering, DOS, cryptographic weakness exploitation 開發

8 8 Wireless PKI Implementation The Entrust Secure Web Portal solution uses both wired and wireless techniques for authentication  Basic security with username/password  Enhanced security with digital signature plan  Enhanced security with two factor authentication

9 9 3 rd Party Services Introduce additional security challenges 挑戰 Entrust 信託 uses digital IDs, tamper- resistant logs, time stamping 戳記, various toolkits to ensure data integrity and confidentiality

10 10 WAP PKI Leaders in WAP PKI – SmartTrust (http://www.smartrust.com)http://www.smartrust.com Focus on infrastructure software for managing securing mobile e-services WAP PKI model  CA PK Certificates used for WTLS Class 2  Client PK Certificates used for WTLS Class 3  Client PK Certificates used with WMLScript SignText

11 11 Server and client certificates in WAP PKI Server certificate  Needs to be downloaded into the WAP client for server (gateway) authentication purposes.  Limited processing capabilities in handling parsing 語法分析 which is required to interpret a standard X.509 certificate

12 12 Server and client certificates in WAP PKI Client certificate  To be capable of handling client authentication for WTLS sessions (WTLS Class 3)  To support WMLScript SignText, which involves digital signatures.  Client certificate information (a certificate URL rather than the complete certificate) is defined to be stored in a WIM (WAP identity Module) but not the complete certificate

13 13 WTLS Class 2 and Class 3 WTLS Class 2  Provide the capability for the client to authenticate the identity of the gateway with which it is communicating.  Identical to SSL  Optimized for low- bandwidth bearer networks with relatively long latency WTLS Class 3  Add client authentication through having the client respond to a challenge during the initial session negotiation  WTLS Class 3 requires access to a private key to sign the challenge message sent from the gateway server.  The private key is stored within a tamperproof device (WIM) stored in the SIM card.

14 14 WMLScript SignText An electronic transaction requires signature as well. WAP SignText() method provides for standardized digital signature on visible text- based content. The Crypto.signText function specifics a signed content format to be used to convey signed data both to and from WAP devices. WAP client browser identifies certain tags in the WMLScript and activates the Crypto.signText function

15 15 WAP Certificate Management Issues Certificates need an issuer, commonly the CA. The CA needs to provide a policy behind certificates that the users understand the trust. All entities need to find and install the CA certificate in a trusted way. More information can be found in the reference book.

16 16 Limitations The server is not compliant with X.509. PKI is considered fairly immature. Does not include status checking of server certificates Short lived (48 hours) certificates

17 17 WAP Security Token – p321 Provide for both tamperproof storage of private keys and execution of the algorithm resulting in a digital signature. A device hosting a WIM exist in 4 different ways  A combined SIM/WIM chip  In a separate SIM and WIM chips  As a dual slot device for an easily-removable WIM  A hardware component WIM effectively built into the device

18 18 WAP Certificate Enrollment WAP-217-WPKI a Proof-of-possession involves having the subject requesting a certificate utilize the private key in the request creating digitally signed data Problem: wireless devices have limited display and computing processing power

19 19 Certificate Request A PKCS #10 request contains an ASN.1- encoded structure of binary data not very suitable for the human eye (or mind). Adjust to human point of view PKI portal restructures the information and create a suitable request to a CA. PKI portal takes the role of a registration authority (RA).

20 20 Certificate Delivery – 2 ways WIM will not contain any details about the certificate other than the public key identity. To deliver a full X.509 corticated, or a pointer location to the actual location of the issued certificate. This requires the WIM to be capable of receiving an over-the-air update with the relevant data.

21 21 Device Certificate The device manufacturer’s quality guarantee regarding the key, the device storing the key, and related procedures. Security of the key pair needs to be guaranteed by the manufacturer or issuer) of the device.


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