Crypto in information security Elmira ebrahimi, nazanin bayati, mona porbidei, shaghayegh arabnia Teacher:ms.raeisian Fall2015 Shariaty technical college

Introduction Developing in computer network Secure data???? Crypto via key The Roman Empire Most users, especially "encrypt information, Governments and military users

Information security The protection of information and information systems from unauthorized activities reach out, Disclosure, read, copy or record, manipulate, change, wreck.

Information security Significant impact on the privacy of information security Fields can work: Securing networks and Infrastructure securing applications and data bases security testing auditing and information systems program review Planning the continuation of trade and reviews of electronic crimes, etc.

Base concepts As the definition of information security, privacy, integrity means and availability information from unauthorized individuals

"Availability" "integrity“ "Confidentiality"

availability The information should be when needed by authorized persons are available

integrity Integrity means that the data will prevent unauthorized change detection and change the information in the event of unauthorized tampering

Confidentiality means that prevent information disclosure to unauthorized individuals In credit card, card number is encrypted Privacy breach Like s.o. look at your data or send your data by mobile

Access control To secure information Limited to authorized people Higher secure higher mechanism Mechanism use authorization

authorization What u are? What u have? What u know?

Science of Encryption Encryption Decryption

Science of encryption The science of codes and passwords Need to prove the identity of the sender and the recipient The message In the meantime Should not change the content of the message to make sure

Encryption The operational initial data using an algorithm and a key becomes a non-understandable text no access to key, access to information from the encrypted text is impossible

decryption A device or program that encrypted data returns to the first State The change of non-readable codes to text readable

Applications of cryptography Credit card information The issue of membership in the forums Private information Details of the personal information Sensitive information in an organization Information relating to bank accounts

Crypto Cryptography  making “secret codes” Cryptanalysis  breaking “secret codes” Crypto  all of the above (and more) 17

Definitions of cryptography (plaintext) (Ciphertext) (key) 18

Algorithms Basic assumption This is known as Kerckhoffs’ Principle The system is completely known to the attacker Only the key is secret That is, crypto algorithms are not secret This is known as Kerckhoffs’ Principle Why do we make this assumption? 19

History 20

Simple Substitution Ciphertext: Khoor Jxbv Shift by 3 Plaintext HELLO GUYS Key: a b c d e f g h i j k l m n o p q r s t u v w x y D E F G H I J K L M N O P Q R S T U V W X Y Z A B z C Plaintext Ciphertext Ciphertext: Khoor Jxbv Shift by 3 21

Caesar’s cipher http://enigma.louisedade.co.uk/howitworks.html 22

Double Transposition 23

One-time Pad: Encryption e=000 h=001 i=010 k=011 l=100 r=101 s=110 t=111 24

Taxonomy of Cryptography Symmetric Key Same key for encryption and decryption Two types: Stream ciphers _ like a one-time pad, Block ciphers Public Key (or asymmetric crypto) Two keys, one for encryption (public), and one for decryption (private) Also, digital signatures  nothing comparable in symmetric key crypto Hash algorithms Sometimes viewed as “one way” crypto 25

Symmetric Key Crypto Stream Ciphers Once upon a time, the king of crypto Today, not as popular as block ciphers A5/1 Based on shift registers Used in GSM mobile phone system 26

A5/1 maj(x8, y10, z10)     X Y Z 27 x0 x1 x2 x3 x4 x5 x6 x7 x8 x9

Block Ciphers Plaintext and ciphertext consist of fixed-sized blocks Ciphertext obtained from plaintext by iterating a round function Input to round function consists of key and the output of previous round Usually implemented in software Data Encryption Standard(DES) Advanced Encryption Standard(AES) 28

Public Key Cryptography Two keys Sender uses recipient’s public key to encrypt Recipient uses private key to decrypt Based on “trap door one way function” RSA is the gold standard in public key crypto 29

Hash Function Crypto hash function h(x) must provide Compression output length is small Efficiency h(x) easy to compute for any x One-way given a value y it is infeasible to find an x such that h(x) = y 30

Visual Cryptography If a pixel is black, randomly choose c or d If a pixel is white, randomly choose a or b for Alice’s/Bob’s shares If a pixel is black, randomly choose c or d no info from one share 31

منابع http://wikipedia.org/wiki/(computer_security) www.irannetbook.com Wikipedia hit.mums.ac.ir www.sarzaminDownload.com www.certcc.ir

Question ??

Thanks For Listening