Welcome! Welcome! Welcome! Welcome! What will happen today? What - PowerPoint PPT Presentation

th January 2008 20 th 20 January 2008 University College London University College London Welcome! Welcome! Welcome! Welcome!

What will happen today? What will happen today? Lecture Lecture - - bear with us, will start in a minute! bear with us, will start in a minute! Tour around UCL Tour Tour around UCL Tour around UCL around UCL will give you a taste of an academic life. will give you a taste of an academic life. Workshops Workshops: : try to use what you’ve learnt. try to use what you’ve learnt.

Cryptography Cryptography Better don’t get confused! Better don’t get confused!

First First things things first first

First First things things first first Cryptography Cryptography

First First things things first first Cryptography Cryptography

First First things things first first Cryptography Cryptography κρυπτός [ κρυπτός κρυπτός [ κρυπτός [ kryptos [ kryptos kryptos ] kryptos ] ] ] "secret" "secret" γράφω γράφω [ [ gráphō ] "I write" write"

First First things things first first Cryptography Cryptography κρυπτός κρυπτός [ κρυπτός [ κρυπτός [ kryptos [ kryptos kryptos ] kryptos ] ] ] "secret" "secret" γράφω γράφω [ [ gráphō ] "I write" write" Steganography Stegano graphy

First First things things first first Cryptography Cryptography κρυπτός κρυπτός [ κρυπτός [ κρυπτός [ kryptos [ kryptos kryptos ] kryptos ] ] ] "secret" "secret" γράφω γράφω [ [ gráphō ] "I write" write" Steganography Stegano graphy

First First things things first first Cryptography Cryptography κρυπτός κρυπτός [ κρυπτός [ κρυπτός [ kryptos [ kryptos kryptos ] kryptos ] ] ] "secret" "secret" γράφω [ γράφω [ gráphō ] "I write" write" "covered " covered" " Steganography Stegano graphy

Steganography Steganography - - examples examples

Steganography Steganography - - examples examples http://www.mcbworld.com/mcbworld/gadget-c-3.html

Steganography Steganography - - examples examples http://lawngospel.wordpress.com/2008/10/12/the-redeemed- tattoo-if-were-gonna-ink-wed-better-think/ http://www.mcbworld.com/mcbworld/gadget-c-3.html

More about cryptography More about cryptography

More about cryptography More about cryptography � CODE WORDS CODE WORDS �

More about cryptography More about cryptography � CODE WORDS CODE WORDS � apple pie = prepare the attack apple pie = prepare the attack mum’s favourite broom = enemies mum’s favourite broom = enemies

More about cryptography More about cryptography � CODE WORDS CODE WORDS � � � TRANSPOSITION CIPHER TRANSPOSITION CIPHER

More about cryptography More about cryptography � CODE WORDS CODE WORDS � � � TRANSPOSITION CIPHER TRANSPOSITION CIPHER need a break need a break = = ende a rbaek ende a rbaek

More about cryptography More about cryptography � CODE WORDS CODE WORDS � � � TRANSPOSITION CIPHER TRANSPOSITION CIPHER � � SUBSTITUTION CIPHER SUBSTITUTION CIPHER

More about cryptography More about cryptography � CODE WORDS CODE WORDS � � � TRANSPOSITION CIPHER TRANSPOSITION CIPHER � SUBSTITUTION CIPHER � SUBSTITUTION CIPHER 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 Z A B… 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 Z A B… fly f ly = ekx = ekx (1 place to the left (1 place to the left) ) rainbow = udlqerz rainbow = udlqerz (3 places to the right) (3 places to the right) � � Caesar cipher Caesar cipher

More about cryptography More about cryptography � CODE WORDS CODE WORDS � � � TRANSPOSITION CIPHER TRANSPOSITION CIPHER � � SUBSTITUTION CIPHER SUBSTITUTION CIPHER � � S SYMBOLIC CIPHER YMBOLIC CIPHER

More about cryptography More about cryptography � CODE WORDS CODE WORDS � � � TRANSPOSITION CIPHER TRANSPOSITION CIPHER � � SUBSTITUTION CIPHER SUBSTITUTION CIPHER � � S SYMBOLIC CIPHER YMBOLIC CIPHER I am hungry = I am hungry =

More about cryptography More about cryptography � CODE WORDS CODE WORDS � � � TRANSPOSITION CIPHER TRANSPOSITION CIPHER � � SUBSTITUTION CIPHER SUBSTITUTION CIPHER � � S SYMBOLIC CIPHER YMBOLIC CIPHER � many more… � many more…

Right… but how to crack the code? Right… but how to crack the code?

Right… but how to crack the code? Right… but how to crack the code? http://www.thedavincigame.com/Code_breaking.html http://www.thedavincigame.com/Code_breaking.html

Kid Kid- -RSA RSA RSA creators: RSA creators: Ron Rivest, Ron Rivest, Adi Shamir Adi Shamir Leonard Adleman Leonard Adleman RSA was first RSA was first described in 1977. described in 1977. One of the two most popular ways of coding a message. One of the two most popular ways of coding a message. Kid Kid- -RSA: RSA: proposed by Neal Koblitz proposed by Neal Koblitz

Quick recap Quick recap � � integer integer � � modulo modulo � public key � public key public key and public key and and private key and private key private key private key � � encryption encryption plaintext plaintext ciphertext ciphertext decryption decryption

Here it comes… ! Here it comes… !

Here it comes… ! Here it comes… ! Remember: letters are just symbols, Remember: letters are just symbols, you can use pictures if you find it easier! you can use pictures if you find it easier! M M = = a a * * b b - -1 1 is essentially the same as: is essentially the same as: � � � � � -1

Bibliography Bibliography 1. 1. http://www.scribd.com/doc/2345053/Modular http://www.scribd.com/doc/2345053/Modular- -Arithmetic Arithmetic- -RSA RSA- -Encryption Encryption 2. 2. http://www.math.washington.edu/~koblitz/crlogia.html http://www.math.washington.edu/~koblitz/crlogia.html 3. 3. http://www.cs.uri.edu/cryptography/publickeykidkrypto.htm http://www.cs.uri.edu/cryptography/publickeykidkrypto.htm 4. 4. http://www.mathaware.org/mam/06/Sauerberg_PKC http://www.mathaware.org/mam/06/Sauerberg_PKC- -essay.html essay.html 5. 5. http http://axion.physics.ubc.ca/crypt.html#RSA ://axion.physics.ubc.ca/crypt.html#RSA 6. 6. http://www.answers.com/RSA http://www.answers.com/RSA 7. 7. http://www.mcld.co.uk/decipher/ http://www.mcld.co.uk/decipher/ 8. 8. http://www.exploratorium.edu/ronh/secret/secret.html http://www.exploratorium.edu/ronh/secret/secret.html 9. 9. http http://en.wikipedia.org/wiki/Cryptography ://en.wikipedia.org/wiki/Cryptography 10. 10. http://en.wikipedia.org/wiki/Steganography http://en.wikipedia.org/wiki/Steganography 11. 11. http://en.wikipedia.org/wiki/Public_key http://en.wikipedia.org/wiki/Public_key