Security - What is network security? Confidentiality: only...

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What is network security? Confidentiality: only sender, intended receiver should “understand” message contents sender encrypts message receiver decrypts message Message Integrity: sender, receiver want to ensure the validity of a transmitted message. It deals with methods that ensure that the contents of a message have not been tampered with and altered. Authentication: sender, receiver want to confirm identity of each other Access and Availability: services must be accessible and available to users
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Message Confidentiality and Integrity Message Confidentiality is the property that the original plaintext message cannot be determined by an attacker who intercepts the ciphertext ( A text in encrypted form ) . Message Integrity is the property that the receiver can detect whether the message sent (whether encrypted or not) was altered in transit or afterwards. The two are thus different concepts, and one can have one without the other.
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Friends and enemies: Alice, Bob, Trudy In network security world Bob, Alice (lovers!) want to communicate “securely” Trudy (intruder) may intercept, delete, add messages secure sender receiver channel data, control messages data Alice Bob Trudy
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There are bad guys (and girls) out there! Q: What can a “bad guy” do? A: a lot! eavesdrop: intercept messages actively insert messages into connection impersonation: can fake (spoof) source address in packet (or any field in packet) hijacking: “take over” ongoing connection by removing sender or receiver, inserting himself in place denial of service : prevent service from being used by others (e.g., by overloading resources)
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Security Mechanisms Three basic building blocks are used: 1. Encryption is used to provide confidentially, and can provide authentication. 2. Checksums/hash algorithms are used to provide integrity protection, can provide authentication. 3. Digital signatures are used to provide authentication, integrity protection, and non- repudiation (non-refusal). One or more security mechanisms are combined to provide a security service.
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Services, Mechanisms, Algorithms A typical security protocol ( Secure Sockets Layer) provides one or more services Services are built from mechanisms Mechanisms are implemented using algorithms
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Encryption The process of transforming information using an algorithm to make it unreadable to anyone except those possessing a special key.
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Symmetric-key Encryption Allows two parties to agree on a shared key Problem of communicating a large message in secret reduced to communicating a small key in secret
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Encryption Standards The major requirements for a cryptosystem can be stated as follows: To provide an easy and inexpensive means of encryption and decryption to all authorised users in possession of the appropriate key.
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Security - What is network security? Confidentiality: only...

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