wtls (wireless transport layer security) youngho choung yhchoung@cs.uh.edu

WTLSWTLS (Wireless Transport Layer (Wireless Transport Layer

Security)Security)

Youngho ChoungYhchoung@cs.uh.edu

Youngho Choung

ContentsContents

Why we need WTLS?What is WTLS?What is TLS (SSL3.0) ?WTLS FunctionsSecurity AlgorithmWTLS specificationsOther Technologies

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Why we need WTLS ? (1/2)Why we need WTLS ? (1/2)

What can we do through the Cell Phone? Communication Using Internet

E-commerce On-line banking Trading Stock

Electric Cash Electric ID Watching movie, take a picture… etc…

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Why we need WTLS ? (2/2)Why we need WTLS ? (2/2)

Environment problems

We need Security Solutions

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What is WTLS ? (1/2)What is WTLS ? (1/2)

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What is WTLS ? (1/2)What is WTLS ? (1/2)

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What is TLS (SSL3.0) ? (1/3)What is TLS (SSL3.0) ? (1/3)

TLS stand for Transaction Layer SecuritySSL stand for Secure Socket Layer

Customer

웹브라우저

인터넷인터넷Internet

Shopping Mall

불안전한Unreliable Channel

암호화 구간

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What is TLS (SSL3.0) ? (2/3)What is TLS (SSL3.0) ? (2/3)

Application data

Fragment

Compress

Add MAC

Encrypt

Append SSLrecord header

SSLHandshakeProtocol

SSL Change Cipher Spec

Protocol

SSL AlertProtocol HTTP

SSL Record Protocol

TCP

IP

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What is TLS (SSL3.0) ? (3/3)What is TLS (SSL3.0) ? (3/3)

Handshake protocolHandshake protocol

Key establishment algorithmDiffie -Hellman , RSA, Fortezza

Certificate RSA, DSS, Fortezza

Record protocolRecord protocol

MAC algorithmMD5, SHA-1

Encryption algorithmRC2, RC4, DES, Triple DES, IDEA,Fortezza

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WTLS FunctionsWTLS Functions

Data IntegrityPrivacyAuthenticationDoS (Denial of Service) protectionOptional

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Security AlgorithmSecurity AlgorithmHash FunctionHash Function

Dyejsmldmnf

mdfnmd , sdd

fnfnfnlkfekkfe

ekfkjefjefelfee

----------------

Any Length Plain Text

Hash Function

Fix length Encrypted Text

MD5, MD4, Hash, SHA-1, etc

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Security AlgorithmSecurity AlgorithmBlock CipherBlock Cipher

(1) Diagram

M E C(Message) (Ciphertext)

K(Key)

M , C , K : n bit blocksExamples ( in bits)

{128,192,256}{128,192,256}{128,192,256}AES646464DESKCM

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Security AlgorithmSecurity AlgorithmBlock CipherBlock Cipher

(2) Encryption : Combination of Substitution &

Permutation

Decryption : Inverse of Encryption

(3) Classical ciphers

a. Permutation Ciphers

b. Substitution Cipher : Caesar Cipher

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Security AlgorithmSecurity AlgorithmPublic KeyPublic Key

Key distribution is difficult Tow Communicants already share a key or have

the use of a key distribution center

Characteristic (public) encryption key ≠ (private) decryption

key

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Security AlgorithmSecurity AlgorithmPublic KeyPublic Key

Bob'sprivate key

Bob'spublic key

Transmittedciphertext

Encryption Algorithm

Plaintextinput

Joy Ted

Decryption Algorithm

Plaintext output

Alice'spublic key ring

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WTLS Specifications (1/5)WTLS Specifications (1/5)

Handshaking protocol Full handshaking protocol Abbreviated handshaking protocol Optimized handshaking protocol

Alert protocolChange Cipher spec protocolRecord protocol

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WTLS SpecificationsWTLS Specifications

Full handshaking

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WTLS SpecificationsWTLS Specifications

Abbreviated handshaking

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WTLS SpecificationsWTLS Specifications

Optimized full handshaking

[ChangCipherSpec]FinishedApplication Data

ServerHelloCertificate[ChangeCipherSpec]Finished

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WTLS Specifications (4/5)WTLS Specifications (4/5)

Alert protocol

Change Cipher spec protocol

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WTLS Specifications (5/5)WTLS Specifications (5/5)

Record Protocol

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Let’s talk about……later..Let’s talk about……later..

WALS(Wireless Application Layer Security)WPKI(Wireless Public-Key Infrastructure)WIM(WAP Identity Module References