How Spies Communica –

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  • HOW SPIESCOMMUNICATE

    Copyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved.

    General Knowledge for Kidsmocomi.com/learn/general-knowledge/

  • HOW SPIESCOMMUNICATE

    (Encryption) (Decryption)

    Cryptography also known as cryptology is the practice and study of techniques used for secure communication in the presence of third parties.

    Copyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved.

  • HOW SPIESCOMMUNICATE

    Cryptography techniques prior to the modern age was eectively synonymous with encryp-tion - the conversion of information from a read-able state to apparent visible nonsense. The person or originator of an encrypted message shared the decoding technique needed to re-cover the original information only with in-tended recipients, thereby preventing un-wanted persons to do the same.

    Copyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved.

  • HOW SPIESCOMMUNICATE

    Since World War I and the invention of the com-puter, methods used to carry out cryptology have become extremely complex and its appli-cation more widespread. Cryptography today uses the disciplines of mathematics, computer science, and electrical engineering. The applica-tion of cryptography is now used for ATM cards, computer passwords, and electronic commerce.

    Copyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved.

  • HOW SPIESCOMMUNICATE

    Cipher Machine

    Until modern times cryptography referred almost exclusively to encryption, which is the process of converting plain text into cipher text. Decryption is the reverse, in other words, moving from the cipher text back to plain text.

    Terminology

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  • HOW SPIESCOMMUNICATE

    Cipher OutputCopyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved.

  • HOW SPIESCOMMUNICATE

    History of cryptography and cryptanalysis

    A cipher (or cypher) is a pair of algorithms that create the encryption and the reversing decryp-tion. The operation of a cipher is controlled both by the algorithm and in each instance by a "key". The "key" is a secret parameter known only to the communicants for the specic exchange of messages.

    Cryptanalysis is the study of how to crack en-cryption algorithms or their implementations.

    Before the modern era, cryptology was con-cerned solely with encryption. Encryption was used to attempt to ensure secrecy in communi-cations, such as those of spies, military leaders, and diplomats.

    Copyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved.

  • HOW SPIESCOMMUNICATE

    Cryptanalysis

    In recent times, the eld has expanded beyond condentiality concerns and now include tech-niques for message integrity checking, sender/receiver identity authentication, digital signatures, interactive proofs and secure com-putation, among others.

    Copyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved.

  • HOW SPIESCOMMUNICATE

    Cryptography

    Classic cryptography

    The earliest forms of secret writing required little more than pen and paper, as most people could not read. Those who were more literate and had literate opponents required actualy cryptography.

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  • HOW SPIESCOMMUNICATE

    Caesar Cipher

    The main classical cipher types are transposition ciphers, which rearrange the order of letters in a message (e.g., 'hello dolly' becomes 'ehlol yllod' in a simple rearrangement scheme, and substi-tution ciphers, which systematically replace let-ters or groups of letters with other letters or groups of letters (e.g., 'y at once' becomes 'gmz bu podf') by replacing each letter with the one following it in the Latin alphabet). These simple versions however have never oered much con-dentiality from enterprising opponents.

    A P P L E

    D S S O H

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  • HOW SPIESCOMMUNICATE

    Cipher machine in the shape of a book

    An early substitution cipher was the Caesar cipher, in which each letter in the plaintext was replaced by a letter some xed number of posi-tions further down the alphabet. Suetonius, a Roman historian reports that Julius Caesar used it with a shift of three to communicate with his generals.

    Atbash is an example of an early Hebrew cipher. The earliest known use of cryptography is some carved ciphertext on stone in Egypt at around 1900 BCE.

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  • HOW SPIESCOMMUNICATE

    Computer era

    Many mechanical encryption/decryption de-vices were invented early in the 20th century, and several patented, among them the rotor machinesfamously including the Enigma ma-chine used by the German government and military from the late '20s and during World War II. The ciphers implemented by these machines brought about a substantial increase in crypta-nalytic diculty after WWI.

    Cryptanalysis of the new mechanical devices proved to be both dicult and laborious. In Great Britain, cryptanalytic eorts during WWII spurred the development of more ecient means for carrying out repetitious tasks.

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  • HOW SPIESCOMMUNICATE

    Copyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved. Smart Card

    This culminated in the development of the Co-lossus, the world's rst fully electronic, digital, programmable computer, which assisted in the decryption of ciphers generated by the German Army's Lorenz SZ40/42 machine.

    Just as the development of digital computers and electronics helped in cryptanalysis, it made possible much more complex ciphers.

  • HOW SPIESCOMMUNICATE

    Copyright 2012 Mocomi & Anibrain Digital Technologies Pvt. Ltd. All Rights Reserved.

    Image references:Cipher machine/Cipher output/Cryptanalysis/Cryptography/Cipher machine in the shape of a book/Smart card - source: www.wikipedia.org. This file is licensed under the creative commons attribution Share Alike.

    Magnifying Glass/computer - source: www.openclipart.org. This image is public domain. You may use this picture for any purpose, including commercial.

    Furthermore, computers allowed for the encryp-tion of any kind of data unlike classical ciphers which only encrypted written language texts. Computer use has thus supplanted linguistic cryptography, both for cipher design and cryptanalysis.

    Decode these substitution ciphers. (J bn dszqu-bobmztu)

    Start communicating with your friends in school through code. Those chits you pass on hence-forth will always be safe.

    Project

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