CIPHERS

CIPHERS

1. VIGENERES CIPHER

   • Extension of caesar cipher
   • Polyalphabetic cipher that uses mulitple alphabets
   • The key is much longer making it harder to crack the code
   • EG) the key could be 8,3,5,9,1
   • Weakness: repeating the key.
     • If guessed correctly can be treated as multiple caesar ciphers that are easy to crack

2. CAESAR CIPHER

   • Each letter of the plaintext is replaced by another letter
   • A fixed number of letters down the alphabet
   • EG) with a left shift of 3, A=X
   • Simple encryption technique
   • Substitution cipher
   • Weakness: only 25 possible keys
     • With E the most common used letter, and T commonly used at beginning of words - this cipher is easy to crack

3. DES (DATA ENCRYPTION STANDARD)

   • Uses 16 rounds of diffusion on groups of 8 plaintext letters
     • Takes 8 letters in binary and encrypts them
       • Resulting in more than a quadrillion key possibilities
   • Substiution and transposition
     • Substitution: using multiple alphabets
     • Transposition: used on plaintext to scramble letters
       • EG) Attack = ttacka
   • Weakness: Todays technology
     • Although in the 70s this would have taken years to crack, todays technology on computers can be done in a day