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Learning Cryptography through handcyphers or the encryption 101 If you understand the basics of cryptography you're more able to understand the tools and thus apply the technology better It's not too complex! It's not too complex! In this

  1. Learning Cryptography through handcyphers or the encryption 101

  2. If you understand the basics of cryptography you're more able to understand the tools and thus apply the technology better It's not too complex! It's not too complex!

  3. In this hour ● Who's bullshitting today? ● Why cryptography? ● Working on handcyphers? ● Now what?

  4. In this hour ● Who's bullshitting today? ● Why cryptography? ● Working on handcyphers? ● Now what?

  5. Who's bullshitting today? ● Brenno de Winter, 34, single, male, open source minded, freedom loving, technology savvy, stubborn, community playing, overactive, news junk. ● Started programming at age of 6, explored the security options in the world

  6. Who's Bullshitting today? ● Today I'm freelancejournalist for several publications, so I: – Write about technology; – Teach it; – Talk about it; – Consult it; – Participate in the community.

  7. In this hour ● Who's bullshitting today? ● Why cryptography? ● Working on handcyphers? ● Now what?

  8. Why cryptography? Because it is a security tool helping us keep secrets secret and help us perform authentication

  9. Cryptography is a great privacy tool

  10. Privacy? I've got nothing to hide ● Well you do! Wanna debate? After the session ● It is a civil liberty and a human right ● Needed for: – fundamental basis for maintaining democracy; – thus protection from totalitarian-regimes; – needed to maintain freedom of speech; – a personal live; – protection against crimes; – protection against data theft;

  11. The question is really Who do we award with privacy and who should be transparent?

  12. Are you afraid of your government? ● Yes! They can't deal with information: – Dutch lawful interception centers are not protected well enough (study); – DA's place their computer with sensitive data and their kiddy porn on the street as garbage; – Clueless agents share sentive files through Kazaa; – Laptops with data (unencrypted) were stolen from a police station – The secret service leaves state secrets in rental cars and laptops in train; – There is little democratic control on secret service;

  13. So encryption? Yeah to decrease the change of abuse by third parties

  14. In this hour ● Who's bullshitting today? ● Why cryptography? ● Working on handcyphers? ● Now what?

  15. Working on handcyphers? Well good to understand how algorithms grew to what they are Handcyphers: Basically pen and paper algorithms

  16. Ceasar Rotation (ROT) ● The alphabet shifts x-positions ● ROT-13 ABCDEFGHIJKLMNOPQRSTUVWXYZ -> NOPQRSTUVWXYZABCDEFGHIJKLM So: CHAOS COMPUTER CAMP becomes PUNAE PAYBGFRD PNYB

  17. Downside ● Easy to crack, only 26 options ● ROT-13 is the most popular so a good starting point ● It was still used “professionally” in 2001

  18. Mono Alphabetic substition Every letter is replaced by another character A B C D E F G H I J K L MN O P Q R S T U V WX Y Z B D K I C Y R S J L X Z N P MG R T U V O WF A H E “Legal” becomes “Zcrbz” No we're “totally secure”, since we have 26*25*...*1 possibilities

  19. Also limited in protection ● Did you ever play Hangman?

  20. So this can be cracked too? Character Times per ● The code was safe until the 9 th 1,000 characters century when statistical data on E 159 N 86 character usage was found A 63 ● No alternative available until T 56 R 54 1553 D 51 O 48 I 47 S 35 L 31 G 28

  21. Vigenère ● Use of encryption through a shared key ● Using poly alphabetic substitution ● Giovanni Batista Belaso inventor, Blaise de Vigenère made the world aware

  22. 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 | 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 B | 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 C | 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 D | 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 C E | E F G H I J K L M N O P Q R S T U V W X Y Z A B C D F | F G H I J K L M N O P Q R S T U V W X Y Z A B C D E G | G H I J K L M N O P Q R S T U V W X Y Z A B C D E F H | H I J K L M N O P Q R S T U V W X Y Z A B C D E F G I | I J K L M N O P Q R S T U V W X Y Z A B C D E F G H J | J K L M N O P Q R S T U V W X Y Z A B C D E F G H I K | K L M N O P Q R S T U V W X Y Z A B C D E F G H I J L | L M N O P Q R S T U V W X Y Z A B C D E F G H I J K M | M N O P Q R S T U V W X Y Z A B C D E F G H I J K L N | N O P Q R S T U V W X Y Z A B C D E F G H I J K L M O | O P Q R S T U V W X Y Z A B C D E F G H I J K L M N P | P Q R S T U V W X Y Z A B C D E F G H I J K L M N O Q | Q R S T U V W X Y Z A B C D E F G H I J K L M N O P R | R S T U V W X Y Z A B C D E F G H I J K L M N O P Q S | S T U V W X Y Z A B C D E F G H I J K L M N O P Q R T | T U V W X Y Z A B C D E F G H I J K L M N O P Q R S U | U V W X Y Z A B C D E F G H I J K L M N O P Q R S T V | V W X Y Z A B C D E F G H I J K L M N O P Q R S T U W | W X Y Z A B C D E F G H I J K L M N O P Q R S T U V X | X Y Z A B C D E F G H I J K L M N O P Q R S T U V W Y | Y Z A B C D E F G H I J K L M N O P Q R S T U V W X Z | Z 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

  23. Using the table ● Encryption goes like this LEGALILLEGALSCHEISSEGAL SECRETSECRETSECRETSECRE DIIRPBDPGXEEKGJVMLKIIRP ● Remarks: – Of course ought to be without spaces – Exchanging passphrase is a pain – How many shared secrets do you need?

  24. Cracking ● Shared secret is the key -> longer passphrases make the algorithm stronger ● Phrase repeats itself, so it can be cracked

  25. Enhancing with autokey ● The solution is using infinite keys ● Using the message as a key ● Keyword: SECURITY ● Message: THIS IS AN IMPORTANT MESSAGE ● Rolling keyword: SECURITYTHISISANIMPORTANTMESSAGE

  26. Homophone Substitution ● Alternative to polyform substition ● Attachting multiple numbers to a letter ● A 11 28 48 62 64 ● B 10 37 ● C 20 47 61 ● D 00 38 59 ● E04 25 29 49 60 63 73 ● etc.

  27. Substitution isn't enough ● Characters are still replaced ● Experience will lead to cracking ● Solution: shuffling of characters

  28. Bifid-table ● We build a 5 by 5 table based on a passphrase ● Passphrase: hackersconference ● Message: I understand cryptography

  29. The table 1 2 3 4 5 1 H A C K E 2 R S O N F 3 B D G I J 4 L M P Q T 5 U V W XY Z

  30. The first coding ● Message: IUNDERSTANDCRYPTOGRAPHY ● Horizontal: 41 425125242314353312314 ● Vertical: 35 231224123125442321415 ● Now encrypt with the numbers per line ● so 41 42 51 .... 35 23 12 24 ● Encrypted: KNEVMDLWGRCXDRMRCVQDAKU

  31. In this hour ● Who's bullshitting today? ● Why cryptography? ● Working on handcyphers? ● Now what?

  32. Now what? ● Use what you know, play with it ● Keep learning and learn more cyphers ● Learn about PKI and PGP ● Code open source apps ● Work on user-friendly encryption technologies ● Use it in: e-mail, webservers, instant messaging, etc. ● Don't stop defending civil liberties

  33. Share knowledge! Subscribe to my monthly newsletter Dutchies listen to my podcast (http://ictroddels.nl) it's free http://dewinter.com - brenno@dewinter.com (C222 6DD2 8BB9 9DD9 0EFD 73DF 306B 21C2 A094 F1D9 )

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