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Published byUriel Chevis Modified over 10 years ago
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SSL/TLS Protocol Network Security Gene Itkis
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Basic paradigmatic application: on-line purchase Client contacts Server (possibly for the first time) Spontaneity Client conveys secret info to Server Confidentiality Whos on the other side? Server Authentication – required Client authentication – optional You do not want to know about security Transparency Allows other protocols to work over SSL/TLS
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Design Goals Confidentiality Authentication Server – required Client – optional Spontaneity Transparency Message Integrity Expandability Fix problems of v.2 SSL v.2 SSL v.3
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Protocol parts Handshake Authenticated Key Establishment Data transfer Encryption Integrity (Message Authentication)
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Handshake protocol outline CS ClientHello ServerHello ClientHello : Version Cipher Suit s Random ServerHello : Version Cipher Suit Session ID Random Certificate + Done Certificate : Subject Issuer (CA) Signed PK RSA ClientKE Data transfer Keys computed ClientKeyExchange : Pre-Master Key encrypted w/PK Attacks Attacks : force weak cipher suit replay: e.g., cause multiple payments Remedy : Random in Hello Check under protection: Finished msgs finished
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Finished & ChangeCipherSpec Data transfer Keys computed finished ClientKE ChangeCipherSpec keys computed ClientFinished ChangeCipherSpec ServerFinished Finished: HASH ( all Handshake msgs) : …
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Handshake protocol outline CS ClientHello ServerHello ClientHello : Version Cipher Suit s Random ServerHello : Version Cipher Suit Session ID Random Certificate Certificate : Subject Issuer (CA) Signed PK DH ClientKE ClientKeyExchange : DH message ServerKE ServerKE + Done ServerKeyExchange ServerKeyExchange : DH message, signed to be verified w/ PK
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