Would You Buy This? Our unbreakable military-grade 10,240-bit - - PowerPoint PPT Presentation

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Would You Buy This? Our unbreakable military-grade 10,240-bit - - PowerPoint PPT Presentation

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Would You Buy This? Our unbreakable military-grade 10,240-bit bi-Gaussian encryption system, using a proprietary one- time pad algorithm, has recently been reviewed by the NSA and approved by a Fortune 500 customer and is available both inside

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SLIDE 1

20 January 2006

Would You Buy This?

Our unbreakable military-grade 10,240-bit bi-Gaussian encryption system, using a proprietary one- time pad algorithm, has recently been reviewed by the NSA and approved by a Fortune 500 customer and is available both inside and outside of the US.

Adapted from Peter Gutman’s crypto tutorial: http://www.cryptoapps.com/~peter/part6.pdf

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SLIDE 2

Alice Bob

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SLIDE 3
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SLIDE 4
  • Message 1 from Criminal to Elsie

Message 2 from Criminal to Elsie Message 3 from Criminal to Elsie Elsie’s Message to the Criminal Message 4 from Criminal to Elsie Sherlock Holmes’ message to the Criminal

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SLIDE 5

The dancing man cipher is another form of a 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

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SLIDE 6

Kerckhoffs’ Principle

“The security of a cryptosystem must not depend on keeping secret the crypto-

  • algorithm. 



 The security depends only on keeping secret the key.”

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SLIDE 7

20 January 2006

Cryptographic Tools

Three basic tools are used


  • Encryption is used to provide confidentiality

  • Checksums/hash algorithms are used to provide

integrity protection


  • Digital signatures are used to provide authentication,

integrity protection, and non-repudiation

However, if the underlying system is unsecure, 
 no amount of cryptography will help.

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SLIDE 8

20 January 2006

General crypto guidance

  • 1. Cryptography is indeed rocket science.

  • 2. Proprietary cryptography must be

assumed to be broken, by definition


  • 3. Adding cryptography to an unsecure

system is like putting steel doors on a grass hut.

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SLIDE 9

Vernam Cipher

If a binary message m1m2...mt is operated on by a binary key string k1k2…kt of the same length to produce a ciphertext c1c2…ct where

ci = mi ⊕ ki , 1 ≤ i ≤ t

If the key string is randomly chosen and never used again, the cipher is a one-time pad and is unbreakable other than via brute-force guessing.

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SLIDE 10

OTP XOR Demo

$ ./xordemo k < p > c $ hexdump -C p 00000000 4d 65 65 74 20 61 74 20 74 68 65 20 67 61 74 68 |Meet at the gath| 00000010 65 72 69 6e 67 20 70 6f 69 6e 74 20 61 74 20 31 |ering point at 1| 00000020 38 30 30 20 68 6f 75 72 73 20 54 68 75 72 73 64 |800 hours Thursd| 00000030 61 79 21 0a |ay!.| 00000034 $ hexdump -C k 00000000 62 61 6e 61 6e 61 6f 72 61 6e 67 65 61 70 70 6c |bananaorangeappl| 00000010 65 6c 69 6d 65 6b 69 77 69 6c 65 6d 6f 6e 6d 61 |elimekiwilemonma| 00000020 6e 67 6f 6b 75 6d 71 75 61 74 70 69 6e 65 61 70 |ngokumquatpineap| 00000030 70 6c 65 0a |ple.| 00000034 $ hexdump -C c 00000000 2f 04 0b 15 4e 00 1b 52 15 06 02 45 06 11 04 04 |/...N..R...E....| 00000010 00 1e 00 03 02 4b 19 18 00 02 11 4d 0e 1a 4d 50 |.....K.....M..MP| 00000020 56 57 5f 4b 1d 02 04 07 12 54 24 01 1b 17 12 14 |VW_K.....T$.....| 00000030 11 15 44 0a |..D.| 00000034 $ ./xordemo k < c > pp $ diff p pp $

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SLIDE 14

Russian One-Time Pad captured by MI5

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SLIDE 15

Auguste Kerckhoffs, ‘La cryptographie militaire’-- 1883

  • 1. The system must be substantially, if not mathematically,

undecipherable;

  • 2. The system must not require secrecy and can be stolen by the

enemy without causing trouble;

  • 3. It must be easy to communicate and remember the keys without

requiring written notes, it must also be easy to change or modify the keys with different participants;

  • 4. The system ought to be compatible with telegraph communication;
  • 5. The system must be portable, and its use must not require more

than one person;

  • 6. Finally, regarding the circumstances in which such system is

applied, it must be easy to use and must neither require stress of mind nor the knowledge of a long series of rules.

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SLIDE 16

Polyalphabetic Substitution Cipher:

Vigenère Cipher

This is the Vigenère Square, or Tabula Recta. P =SAMBRADFORD KEY=HEISMANHEIS C= ZEUTDAQMSZV

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SLIDE 17

Breaking a Vigenère cipher

Frequency analysis fails, because this cipher evens out the distribution of letters. So instead …

  • Search for repeated groups in the ciphertext
  • These may represent the same words encrypted using the

same letters.

  • If they are the same plaintext words, the key should be a

factor of the distances between them

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SLIDE 18

One attack on Vigenère ciphers (Wikipedia)

Key: 
 ABCDABCDABCDABCDABCDABCDABCD 
 Plaintext:
 CRYPTOISSHORTFORCRYPTOGRAPHY 
 Ciphertext: 
 CSASTPKVSIQUTGQUCSASTPIUAQJB
 ^------16------^ Possible key lengths are 16,8,4,2,1

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SLIDE 19

ROTOR Machines

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SLIDE 20

B y M e s s e r W

  • l

a n d

  • w

n w

  • r

k b y u s e r : H a n d i g e H a r r y b a s e d

  • n

p r e v i

  • u

s v e r s i

  • n

b a s e d

  • n


 I m a g e : E n i g m a w i r i n g k l e u r . p n g b y M a t t C r y p t

  • r

i g i n a l l y 
 n l : A f b e e l d i n g : E n i g m a _ w i r i n g _ k l e u r . p n g b y n l : U s e r : D r d e f c

  • m

, 
 C C B Y

  • S

A 3 . , h t t p s : / / c

  • m

m

  • n

s . w i k i m e d i a .

  • r

g / w / i n d e x . p h p ? c u r i d = 1 7 9 4 7 9

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SLIDE 21

General Feistel network

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SLIDE 22

Feistel Networks Guaranteed to be invertible

Original diagram from WikiCommons, modified here

L1 R1 L2 R2

Ld Rd

Ld-1 Rd-1 Ld-2 Rd-2

Then you can add encryption decryption to the F’s.

Ld Rd

Li = Ri-1 Ri = Li-1 XOR f(Ri-1), then Ri = Li-1 XOR f(Ri-1,Ki) )

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SLIDE 23

DES

IP occurs before round 1, transposing the input block in specific manner In each round, the key bits are shifted, and 48 bits are selected from the 56 bits of the key The data is split in half, with permutations and substitutions applied to the right half. After 16 rounds, the FP (inverse of IP) is applied.

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SLIDE 24

AES

Here’s a super animation of AES
 
 hint: play it at 50% or 75% speed

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SLIDE 25

Modes of operation: ECB (Electronic Code Book)

Wikimedia Commons

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SLIDE 26

ECB can leave data patterns behind

Tux the Penguin, the Linux mascot. Created by Larry Ewing with The GIMP. Other two images are from Wikipedia Commons Encrypted using ECB Encrypted using other modes

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SLIDE 27

Initialization Vector (IV)

  • All the modes of operation besides ECB need their pumps

to be primed with a random block of data.

  • No need for secrecy, but an IV should only be used once

for a given key.

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SLIDE 28

Wikimedia Commons

Modes of operation: CBC (Cipher-Block Chaining)

Ci = EK (Pi ⊕ Ci-1) Pi = Ci-1 ⊕ DK (Ci)

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SLIDE 29

Modes of operation: CFB (Cipher Feedback)

Wikimedia Commons

Ci = Pi ⊕ EK (Ci-1) Pi = Ci ⊕ DK (Ci-1)

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SLIDE 30

Cryptographic Hash Function

Wikimedia Commons

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SLIDE 31

Message Authentication Codes

Wikimedia Commons

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SLIDE 33

Playfair Cipher

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

Key is: CHARLES http://www.simonsingh.net/The_Black_Chamber/playfair_cipher.html