Seminar #1 Infosecurity

Kolybelnikov Alexander

kisttan@gmail.com

Agenda

• Organizational matters• Basic terms and defintions• History of cryptography• Infosecurity

Organizational matters

Requirements for seminar courseTask 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

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.

Examination

• 60 points – 3 control works at lectures during the course.

Basic terms and definitions

Cryptography, cryptology, cryptoanalysis

Cryptography (from Greek κρυπτός — ”hidden secret” and γράφω — ”writing”) — the study about methods of information confidentiality and consistency maintenance.

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.

Cryptography, cryptology, cryptoanalysis

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.

• 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.

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.

Cipher, key, encrypting

History of cryptography

History periodicity

• The first period (approximately since the 3rd millennium BC) is characterised by prevalence of monoalphabetic ciphers

• 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

History periodicity

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.

• 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.

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.

History periodicity

Infosecurity

Information transfer system

Infosecurity purposes

• Confidentiality;

• Consistency;

• Accessibility.

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.

Etbash cipher

• Plain text: abcdefghijklmnopqrstuvwxyz Encrypted text: ZYXWVUTSRQPONMLKJIHGFEDCBA

Caesar cipher (Julius)

• Each Caesar from Rome has his own cipher. Julius Caesar cipher became the most well-known.

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.

Vigenere cipher

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.

Unbreakable ciphers – Vernam cipher

Calculating unbreakable ciphers

• DES;• AES;• GOST 28147-89;• Other symmetric and stream ciphers

Ciphers based on unsolved mathematic problems

• RSA;• Diffi-Helman.

Breakable ciphers

• Linear recurrent register;• A5/1;• SkipJack;• etc...