Codes and Cryptography LESSON 1

Cryptography

method of storing and transmitting data in a particular form.

·        includes techniques such as microdots, merging words with images, and other ways to hide information.

BCE

·        Spartan use of scytale, the Egyptians develop hieroglyphic writing

Egyptians

develop hieroglyphic writing and Notable Roman ciphers such as the Caesar cipher.

Leon Battista Alberti

invent polyalphabetic cipher

Polyalphabetic cipher

first mechanical cipher machine.

Joseph Henry

Built an electric device.

Charles Babbage

broke Vigenere’s autokey cipher (the unbreakable cipher of the time).

Marian Rejewski

First break of German Army Enigma in Poland

Charles Bennett & Giles Brassard

designed the first quantum cryptography protocol, BB84.

BB84

first quantum cryptography protocol

Microsoft and its allies

vow to end “full disclosure” of security vulnerabilities by replacing it with “responsible” disclosure guidelines.

Cryptography

the art of writing and solving codes.

·        The study of methods to make and break secret codes.

·        it was used to send secret messages

·        Fundamental part of securing digital communications and data.

·        Intersection of mathematics and security.

Plain Text

Messages that is going to be transmitted or stored is plain text. Anyone can read plain text

Encryption

The method by which we can hide the actual meaning of plain text.

Cipher Text

The result of encryption which results in unreadable gibberish.

Decryption

The method by which the original meaning of cipher text can be recovered (converting cipher text to plaintext.

Key

It is the secret piece of information which is used for encryption and decryption in Cryptography.

Caesar Cipher (Shift Cipher)

one of the simplest forms of encryption.

·        It is a substitution cipher where each letter in the original message (called plain text) is replaced with a letter corresponding to a certain number of letters up down in the alphabet.

Decimation Cipher

Key must be a number that is relatively prime to 26 (numbers in alphabet).’

• Multiply the number representing each letter by the key, and take the result modulo 26.

Shift Ciphers Method

The other way of encrypting and decrypting information