Encryption by dominic.cecilia



  By Ryan Lauer
I501 Nov. 1st, 2001.
Ancient History of Encryption
 First recorded instance
   • Carved 4,000 years ago in present day Egypt in
     the tomb of a nobleman
   • Consisted of unusual Hieroglyphic symbols in
     place of more ordinary ones
   • Inscription was not secret writing
   • Deliberate transformation of writing
  Ancient History of Encryption
 Emerging use of cryptography- 3000 yrs
  • Egypt - secret writing on tombs impress readers
  • India – Kama-sutra, secret writing as one of 64 arts that
    women should know and practice.
  • Mesopotamia – cuneiform tablet (c. 1500 B.C.)
    describing earliest formula for pottery glaze.
  • Greece – (500AD)
     • Spartans establish first system of military cryptography using a
       “skytale”: staff of wood wound with papyrus.
     • Polybius – conversion of letters to numbers using a table
                Polybius Square
           1         2          3   4   5
1          A         B          C   D   E
2          F         G          H   I   J
3          K         L          M   N   O
4          P         Q          R   S   T
5          U         V          W   X   YZ

    For Example:
           24 34 21 35 = INFO
           (24 = I, etc.)
Caesar 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
D E F   G   H   I   J   K L M N     O   P   Q   R   S   T   U V W X       Y   A   B   C

 Julius Caesar
   • Substitution Cipher
   • Shift or offset of two linear alphabets
   • Informatics
   • Used extensively
20th Century Encryption History
 World War I
  • Use of radio for transmission
  • Zimmerman Telegram
 World War II
       • German Armed Services
       • Mechanical encryption using rotors
       • Failure to allow same letter occurances
       • Japanese Wartime Coding Machine
       • Used telephone stepping switches
Modern Encryption
 Components of Encryption
     • Generation
     • Size
     • Safeguard
     •   Transformation of input data (plaintext)
     •   Dependant in some way on the Key
     •   Producing coded message (ciphertext)
     •   Reversible with the key
Modern Encryption
 Methods used today
  • Private Key encryption
     • Specific Key encrypts
     • Decryption uses same key
     • Security?
  • Public Key encryption
     • Fixes Private Key security issue
     • Public Key used to encrypt
     • Private Key used to decrypt
Private Key (symmetric cipher)
 Triple DES
 Blowfish
 RC-2
 RC-4
 Data Encryption Standard
 Approved in 1970s as a federal standard for use in
  unclassified government communications
 128-bit block algorithm developed in 60s by IBM
  called ‘LUCIFER’
 Designed to use a 64-bit key : actually uses 56-bit
  key (weak)
 Vulnerable to Brute Force attack – 18-70
  quintillion letter/number possibilities
Cracking DES
 January 1997, RSA Inc. challenged DES
  with $10,000 prize to break DES.
 Computers aimed to try all 72+ quadrillion
  key possibilities
 Winning group: DESCHALL effort
  – Programmer Rocke Verser links thousands of
    computers via the internet (brute force)
  – 84 days @ 601 trillion keys per day
 Looking for patterns
Public Key Encryption
 Revolutionary Thinking
  – Secure encryption without key sharing??
  – 1976 Stanford University: Whitfield Diffie and
    Martin Hellman publish first paper on subject
 Example
  – Alice wants to send a message to Bob
  – Alice encrypts using Bob’s public key
  – Bob decrypts using his private key
 Why it works
Public Key Encryption
 Theory
  – Relies on the sheer difficulty of factoring very
    large numbers
  – Keys rely on the product of two large prime
  – Very difficult to factor!
  – Public and Private keys are functions of a pair
    of prime numbers 100-300 digits long
 Example of Mathematics Involved
N = P * Q (P,Q prime)
 Public Key Pair { E, N }
   – Used in encryption of message
 Private Key Pair { D, N }
   – Used in decryption of message
 How to find E
 How to find D
 Encryption/Decryption
Who needs encryption?
 Government
   – National Securtity issues
   – Storing classified material
   – Military communication
 Business
   – Consumer confidence
   – Secret and sensitive material
   – E-commerce
 Individual
   – Personal Privacy
   – Medical/Personal records
 Do you think the government has a role in
  controlling encryption? Can it?
 How is the government helped/hurt by
 Do you think e-commerce is ‘safe’ using
  today’s encryption?
 Do you regularly use encryption? For what

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