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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!

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20 20th

th January 2008

January 2008 University College London University College London

Welcome! Welcome! Welcome! Welcome!

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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 Tour around UCL around UCL Tour 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.

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Cryptography Cryptography

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

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First First things things first first

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First First things things first first

Cryptography Cryptography

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First First things things first first

Cryptography Cryptography

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First First things things first first

Cryptography Cryptography

κρυπτός κρυπτός [ [kryptos kryptos] ] κρυπτός κρυπτός [ [kryptos kryptos] ] "secret" "secret" γράφω γράφω [ [gráphō] "I write" write"

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First First things things first first

Cryptography Cryptography

κρυπτός κρυπτός [ [kryptos kryptos] ]

Stegano Steganography graphy

κρυπτός κρυπτός [ [kryptos kryptos] ] "secret" "secret" γράφω γράφω [ [gráphō] "I write" write"

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First First things things first first

Cryptography Cryptography

κρυπτός κρυπτός [ [kryptos kryptos] ]

Stegano Steganography graphy

κρυπτός κρυπτός [ [kryptos kryptos] ] "secret" "secret" γράφω γράφω [ [gráphō] "I write" write"

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First First things things first first

Cryptography Cryptography

κρυπτός κρυπτός [ [kryptos kryptos] ]

Stegano Steganography graphy

" "covered covered" " κρυπτός κρυπτός [ [kryptos kryptos] ] "secret" "secret" γράφω γράφω [ [gráphō] "I write" write"

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Steganography Steganography -

  • examples

examples

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Steganography Steganography -

  • examples

examples

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

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Steganography Steganography -

  • examples

examples

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

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More about cryptography More about cryptography

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More about cryptography More about cryptography

  • CODE WORDS

CODE WORDS

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More about cryptography More about cryptography

apple pie = prepare the attack apple pie = prepare the attack mum’s favourite broom = enemies mum’s favourite broom = enemies

  • CODE WORDS

CODE WORDS

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More about cryptography More about cryptography

  • TRANSPOSITION CIPHER

TRANSPOSITION CIPHER

  • CODE WORDS

CODE WORDS

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More about cryptography More about cryptography

  • TRANSPOSITION CIPHER

TRANSPOSITION CIPHER

  • CODE WORDS

CODE WORDS need a break need a break = = ende a rbaek ende a rbaek

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More about cryptography More about cryptography

  • TRANSPOSITION CIPHER

TRANSPOSITION CIPHER

  • CODE WORDS

CODE WORDS

  • SUBSTITUTION CIPHER

SUBSTITUTION CIPHER

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More about cryptography More about cryptography

  • TRANSPOSITION CIPHER

TRANSPOSITION CIPHER

  • CODE WORDS

CODE WORDS 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… f fly ly = ekx = ekx (1 place to the (1 place to the left left) ) rainbow = udlqerz rainbow = udlqerz (3 places to the right) (3 places to the right)

  • Caesar cipher

Caesar cipher

  • SUBSTITUTION CIPHER

SUBSTITUTION CIPHER

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More about cryptography More about cryptography

  • TRANSPOSITION CIPHER

TRANSPOSITION CIPHER

  • CODE WORDS

CODE WORDS

  • SUBSTITUTION CIPHER

SUBSTITUTION CIPHER

  • S

SYMBOLIC CIPHER YMBOLIC CIPHER

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More about cryptography More about cryptography

  • TRANSPOSITION CIPHER

TRANSPOSITION CIPHER

  • CODE WORDS

CODE WORDS

  • SUBSTITUTION CIPHER

SUBSTITUTION CIPHER

  • S

SYMBOLIC CIPHER YMBOLIC CIPHER I am hungry = I am hungry =

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More about cryptography More about cryptography

  • TRANSPOSITION CIPHER

TRANSPOSITION CIPHER

  • CODE WORDS

CODE WORDS

  • many more…

many more…

  • SUBSTITUTION CIPHER

SUBSTITUTION CIPHER

  • S

SYMBOLIC CIPHER YMBOLIC CIPHER

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

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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

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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

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Quick recap Quick recap

  • public key

public key and and private key private key

  • integer

integer

  • modulo

modulo

  • public key

public key and and private key private key plaintext plaintext ciphertext ciphertext encryption encryption decryption decryption

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Here it comes… ! Here it comes… !

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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
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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