Network Security - Lecture 10

We discussed the basic concept of cryptography Some terminologies such as plain text, ciphertext and key were also discussed. We have seen how keys can be used to encrypt and decrypt the message

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Network SecurityLecture 10Presented by: Dr. Munam Ali Shah Part 2 (b)Cryptography as a Network Security ToolSummary of the previous lectureWe talked about how device security, traffic security and barrier security can help us achieving mobile device security strategy.We also discussed, the RSN and IEEE802.11i standard to ensure more security in our WLAN. 5 phases operation in 11i was also part pf previous lecture discussion And lastly, we discussed the Model for Network Security.Outlines of today’s lectureWe will talk about :What Cryptography is and why is it usedSome basic terminologies such as plain text, cipher text, cryptanalysis will also form part of todays lecture discussionTypes of cryptography attacksObjectivesYou would be able to present an overview of cryptography and how this tool can ensure the network security.Understand the basics phenomenon to deploying cryptography in different environmentsCryptographyThe art of secret writing CryptographyCryptography is the art and science of secrecyHiding one’s secrets has always been human’s desireHistorically, cryptography has been associated with militaryBut now its everywhereCryptography3 interrelated termsCryptologyCryptographyCryptanalysis8 of 164What is cryptology?Cryptology – science of hidingCryptography, Cryptanalysis – hide meaning of a messageSteganography, Steganalysis – hide existence of a messageCryptography – secret writingCryptanalysis – analyzing (breaking) secrets Cryptanalysis is what attacker does Decipher or Decryption is what legitimate receiver doesTerminologyCharactersAliceBobEveTrentPlaintext/messageCiphertext10 of 164TerminologyKeySingle/secret/symmetric keyTwo/public/asymmetric keyEncryption/enciphermentThe conversion of data into ciphertext, that cannot be easily understood by unauthorized people.Decryption/deciphermentThe process of converting encrypted data back into its original form so that it can be understood. 11 of 164Modern cryptography is based onMathematicsComputer scienceCleverness and creativity13CryptographyplaintextmessageciphertextmessageEncryptionDecryptionEncrypted(Information) cannot be read Decrypted(Encrypted(Information)) can beCryptography EncryptDecryptPlaintextCiphertextPlaintextAliceBobEve(active attacker)Insecure ChannelA simple exampleMore simple exampleAnother way to represent the concept of Cryptography 4 types of cryptanalysisDepending on what a cryptanalyst has to work with, attacks can be classified intociphertext only attackknown plaintext attackchosen plaintext attackchosen ciphertext attack (most severe)4 types of attacks Ciphertext only attackthe only data available is a target ciphertext Known plaintext attacka target ciphertextpairs of other ciphertext and plaintext (say, previously broken or guessing)4 types of attacks Chosen plaintext attacksa target ciphertextcan feed encryption algorithm with plaintexts and obtain the matching ciphertextsChosen ciphertext attacka target ciphertextcan feed decryption algorithm with ciphertexts and obtain the matching plaintextsGoals of the AdversaryGet the key (ideally)Get the messageGet part of the message/some information about the messageModel for Network SecurityThis general security model shows that there are four basic tasks in designing a particular security service:Design an algorithm for performing the security-related transformation. The algorithm should be such that an opponent cannot defeat its purpose.Generate the secret information to be used with the algorithm.Develop methods for the distribution and sharing of the secret information.Specify a protocol to be used by the two principals that makes use of the security algorithm and the secret information to achieve a particular security service.Model for Network SecurityNetwork Access Security ModelPrograms can present two kinds of threats Information access threats: Intercept or modify data on behalf of users who should not have access to that data.Service threats: Exploit service flaws in computers to inhibit use by legitimate users.Network Access Security ModelSummary of today’s lectureWe discussed the basic concept of cryptographySome terminologies such as plain text, ciphertext and key were also discussed.We have seen how keys can be used to encrypt and decrypt the messageNext lecture topicsOur discussion on cryptography. Classical ciphers with some examples will be discussedWe will also discuss symmetric and asymmetric cryptography The End

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