INTRODUCTION TO CRYPTOLOGYCryptoanalysts, Encryption, and Decryption

WHAT IS CRYPTOGRAPHY / CRYPTOLOGY The art of protecting information by

transforming it (encrypting it) into an unreadable format, called cipher text.

Only those who possess a secret key can decipher (or decrypt) the message into plain text.

Encrypted messages can sometimes be broken by cryptanalysis, also called codebreaking, although modern cryptography techniques are virtually unbreakable.

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HOW DO YOU THINK THIS CODE WAS ENCRYPTED?

20-15-4-1-25    25-15-21    23-9-12-12   12-5-1-18-14    1-2-15-21-20   3-15-4-5-19 E

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THIS IS CIPHER TEXT

20-15-4-1-25    25-15-21    23-9-12-12   12-5-1-18-14    1-2-15-21-20   3-15-4-5-19

Cipher text Text that has been transformed into an

unreadable format. Code

In cryptology, code means substituting a meaningful word or phrase with another word or phrase to change or hide meaning

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HOW COULD YOU SOLVE THIS CIPHER?

20-15-4-1-25    25-15-21    23-9-12-12 12-5-1-18-14    1-2-15-21-20   3-15-4-5-19

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DID YOU KNOW THAT SOME LETTERS IN THE ALPHABET OCCUR MORE FREQUENTLY IN THE ENGLISH LANGUAGE?

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SOLVE THE CIPHER

20-15-4-1-25    25-15-21    23-9-12-12 12-5-1-18-14    1-2-15-21-20   3-15-4-5-19

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SOLUTION: WHAT IS THE KEY?

A key is symbols, characters, or letters required by the algorithm to encrypt or decrypt a message.

20-15-4-1-25  = today   25-15-21 = you23-9-12-12 = will12-5-1-18-14 = learn 1-2-15-21-20 = about3-15-4-5-19 = codes(and ciphers)

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METHODS OF CRYPTOGRAPHY Substitution

Replacing each letter with a different letter or symbol (a=@, b=J, c=2 so that “a cat” = “@ 2J@”)

Transposition Rearranging the order of letters of the words of a message. (example: “the

letters in each word get moved around = eth ttseelr ni ceah drow etg veodm uarndo”)

Steganography Hiding a message (example: invisible inks, Herodotus tattooed messages on a

shaved slave’s head and waited for the hair to re-grow to hide his messages)

Mathematical Uses advanced formulas to encrypt text

Computer or Mechanically Assisted Using complex algorithms and any single or combination of the mathematical,

transposition, substitution and steganography to encrypt plain text.

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THE ENIGMA MACHINE

The most famous mechanical encryption device in history.

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WHO THINKS UP THIS STUFF?

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WHY DO WE NEED CRYPTANALYSTS

Copyright Protection Security of communications for

Personal Email Businesses Government Military

Credit Card Processing Password Protection

RSA tokens: for business and games (like Warcraft)

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LEGAL PROBLEMS FOR CRYPTANALYSTS

Digital Millennium Copyright Act (1998) Intended to provide law enforcement with a tool to go

after piracy and file sharing (media like music, movies, and software)

Made it illegal to use cryptanalytic techniques to get around the copyright protection methods (called Digital Rights Management)

Unintended result was to limit research and research sharing in the Cryptanalyst field for fear that their work might violate this law. Cryptanalyst argue that the algorithms should be published

so that they can be improved and used. Only the keys should remain a secret.

The first arrest was Dmitry Sklyarov, whose dissertation work and subsequent work with a Russian book reader company identified weaknesses in the protection of PDF files.

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YOU ARE THE CRYPTANALYST! Create your own algorithm for

encrypting a message!

Substitution Replacing each letter with a different letter or symbol (a=@, b=J, c=2 so that

“a cat” = “@ 2J@”)

Transposition Rearranging the order of letters of the words of a message. (example: “the

letters in each word get moved around = eth ttseelr ni ceah drow etg veodm uarndo”)

Steganography Hiding a message (example: invisible inks, Herodotus tattooed messages on a

shaved slave’s head and waited for the hair to re-grow to hide his messages)

Mathematical Uses advanced formulas to encrypt text

Computer or Mechanically Assisted Using complex algorithms and any single or combination of the mathematical,

transposition, substitution and steganography to encrypt plain text.

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