Back to notes

# Caesar cipher

 Keywords: cryptography, encryption, security, algorithms Date: 2020-10-25
• The Caesar cipher is a classic substitution cipher that involves shifting two alphabets in relation to each other to generate a code
• The alphabet can be any arbitrary alphabet, but is commonly the uppercase `[A-Z]` alphabet

• Steps:

1. write the alphabet down two times
2. shift the bottom alphabet by an arbitrary number of positions, known as the key-value
• Consider this example, where the bottom alphabet has been shifted right 3 positions:

``````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
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
``````
• The word "example" would be encoded into "hadpsoh"
• This cipher is named after Julius Caesar, who used this technique to encode military messages

• This is a relatively insecure cipher, since it can be brute-forced with the maximum number of attempts being the length of the alphabet minus 1