Phishing

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Phishing
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Microsoft Vulnerabilities

• Sharp increase in attacks on Windows based PCs in
  1st half of 2004
• 1237 new vulnerabilities or 48/week
• Increase in number of bot networks
• 30,000 from 2,000 in previous 6 months
• Increase in percent of e-commerce attacks from 4
  to 16
• 450 increase in new Windows viruses 4,496

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Spam and E-commerce

• Tim Pigot, Pfizers mens sexual health division
  Pfizer is not the source of Viagra spam
• I, unfortunately get a lot of Viagra spam
  myself Wed love to be able to talk more
  intimately with the people who are interested in
  engaging with us that way. If we didnt live in
  a world full of Viagra spam it would be easier.
• DoubleClick survey the rate at which customers
  open commercial e-mail attached adverts is on the
  decline. Possible causes?
• Spam fatigue
• Fear of phishing

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Introduction to Cryptography
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Cryptography

• Why is cryptography used?
• What applications make use of cryptography?
• What skills make a good crypto-analyst?

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Anagrams

• Conversation Voices rant on
• Desperation A rope ends it
• Militarism I limit arms
• Eric Clapton Narcoleptic
• Madonna Louise Ciccone
• Occasional nude income
• George Bush He bugs Gore

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Terms

• Cryptography
• Plaintext
• Ciphertext
• Algorithm
• Key

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Symmetric Encryption

• Plaintext algorithm ciphertext
• Ciphertext algorithm plaintext
• Problems 1. The algorithm must be good, and 2.
  What do you do about people entering and leaving
  the cryptogroup

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Use of a Key

• Plaintext algorithm key ciphertext
• Ciphertext algorithm key plaintext
• Algorithms are symmetric because both parties
  share the same key

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Vigenéres Cipher

1. Select a key say 1, 23, 14, 6
2. The 1st letter of the plaintext message is
   encrypted finding the plaintext letter in row 1
   and reading the ciphertext letter as the column
   heading, the 2nd letter using row 23, the 3rd
   using row 14, the 4th using row 6, the 5th using
   row 1, etc.
3. To decrypt, find the ciphertext letter in the
   column heading of the appropriate row and read
   the plaintext letter in the cell below.

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Vigenéres Cipher Example
Using the key 1, 23, 14, 6   EVERYONE is
encrypted as   DZQLXRAZ
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(No Transcript)
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Polybius Square

1. Put the letters of the alphabet in a 5X5 matrix.
2. The code for a letter is its (row,column)
3. To decode a letter look at the cell with the
   (row,column). For example, 23 means row 2,
   column 3.

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Example
 
  Encode EVERYONE   15 52 15 43 55 35 34 15
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Letter frequencies in English
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To add complexity

1. Add a key phrase to change the ordering of the
   letters in the matrix.
2. Separate the plaintext into 8 letter groups
   removing blanks.
3. Encode by making the numbers for each 8 letter
   group as follows r(1,2), r(3,4), r(5,6), r(7,8),
   c(1,2), c(3,4), c(5,6), c(7,8)

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Example showing transposition
 
  Encode EVERYONE   15 14 53 31 52 53 55 45
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Example of using a key phrase to create a
Polybius square
 
Lazy grey fox jumps over the quick brown dog
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The Problem of Key Distribution

• Keys must be distributed securely and changed
  regularly
• Keys must also be used securely and destroyed
  securely

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Recognizing Plaintext

• How do you recognize plaintext? It looks like it
  is supposed to, e.g. English, an image
• Unicity distance the amount of ciphertext
  required that reasonable appearing plaintext is
  the true plaintext
• Unicity distance for standard English K/6.8
  where K key length in bits and 6.8 is the
  natural redundancy in English