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- 1. Seminar #1 Infosecurity Kolybelnikov Alexander kisttan@gmail.com
- 2. Agenda • • • • Organizational matters Basic terms and defintions History of cryptography Infosecurity
- 3. Organizational matters
- 4. Requirements for seminar course Task Stage 1 Stage 2 Stage 3 Stage 4 Essay Paper essay: 10 points Article on Wiki +5 points Conference, good article on Wiki + 5 points Featured article on Wiki:50 points Project 10 points Valuable project +5 points (2 projects for a group) Project is marked as good by the commisson of seminarists – +5 points (3 projects for a course) Hometask Upper limit: 10 points
- 5. How to pass the tasks • Essay – defence at the seminar; • H/w – send to e-mail kisttan@gmail.com before a deadline; • Project – defence at the seminar; • Tests – at the seminars.
- 6. Examination • 60 points – 3 control works at lectures during the course.
- 7. Basic terms and definitions
- 8. Cryptography, cryptology, cryptoanalysis Cryptography (from Greek κρυπτός — ”hidden secret” and γράφω — ”writing”) — the study about methods of information confidentiality and consistency maintenance.
- 9. Cryptography, cryptology, cryptoanalysis Cryptology (from Greek κρυπτός — ”hidden secret” and λόγος — ”word”) — the study about encrypting and decrypting methods. Cryptology consists of two parts: cryptography and cryptoanalysis. Cryptography studies development of data encrypting methods. Cryptoanalysis – estimation of strong and week sides of encrypting methods and development of methods allowing to break cryptosystems.
- 10. Cipher, key, encrypting • Cipher is a reversible way of information transformation using a key. The aim of a cipher is to ensure information confidentiality. Algorithms of cryptography transformations reflecting the multitude of plain texts M to the multitude of possibly encrypted data C with the use of key K.
- 11. Cipher, key, encrypting • Key K: secret and/or public (paired with the secret one) component of a cipher that allows reflecting of plain texts M multitude to plain texts C multitude. • Encrypting is the process of plain text transformation to encrypted text with the use of a cipher and a key.
- 12. Cipher, key, encrypting • Decryption (russian: расшифрование) – the process of encrypted text transformation to plain text with the use of a cipher and a key. • De-encryption (дешифрование) – receiving of plain data according to known secret data without knowing a key.
- 13. History of cryptography
- 14. History periodicity • The first period (approximately since the 3rd millennium BC) is characterised by prevalence of monoalphabetic ciphers
- 15. History periodicity • The second period (since the IX century in the Middle East (Al-Kindi) and since the XV century in Europe (Leon Battista Alberti) before the beginning of the XX century) is characterized by the use of polyalphabetic ciphers
- 16. History periodicity • The third period (since the beginning and to the middle of the XX century) is characterized by introduction of electromechanical devices in work of crytpographers. Polyalphabetic ciphers were also widely used.
- 17. History periodicity • The fourth period (since the middle to the 70th years of the XX century) is characterized by transition to mathematical cryptography. Shannon's work: strict mathematical definitions of information amount, data transmission, entropy, encrypting functions.
- 18. History periodicity • The modern period of cryptography development (since the end of the 1970th years to the present) is characterized by the origin and development of the new derection — cryptography with a public key.
- 19. Infosecurity
- 20. Information transfer system
- 21. Infosecurity purposes • Confidentiality; • Consistency; • Accessibility.
- 22. Monoalphabetic ciphers • Monoalphabetic cipher (cipher of simple replacement, simple sustitution cipher) is a class of encrypting methods that define mapping of each letter of encrypted text to the letter of plain text. • Examples: – Etbash; – Caesar ciphers; – etc.
- 23. Etbash cipher • Plain text: abcdefghijklmnopqrstuvwxyz Encrypted text: ZYXWVUTSRQPONMLKJIHGFEDCBA
- 24. Caesar cipher (Julius) • Each Caesar from Rome has his own cipher. Julius Caesar cipher became the most wellknown.
- 25. Polyalphabetic cipher • Polyalphabetic cipher is cyclic application of several monoalphabetic ciphers to a certain number of letters of the encrypted text. • Examples: – Vigenere cipher; – Gronsfeld cipher.
- 26. Vigenere cipher
- 27. Stability of ciphers • All ciphers are divided into several classes of stability: – unbreakable (absolutely unbreakable) ciphers; – calculating unbreakable ciphers; – ciphers based on solution of a mathematic task that is unsolved yet; – breakable ciphers.
- 28. Unbreakable ciphers – Vernam cipher
- 29. Calculating unbreakable ciphers • • • • DES; AES; GOST 28147-89; Other symmetric and stream ciphers
- 30. Ciphers based on unsolved mathematic problems • RSA; • Diffi-Helman.
- 31. Breakable ciphers • • • • Linear recurrent register; A5/1; SkipJack; etc...

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