Encryption

• Plaintext- Data in human-readable form.
• Cipher text- data that has been encrypted.

• Two data encryption techniques are Caesar and Vernum.

• Caeser Cipher- A substitution cipher where one character of plaintext is substituted for another, which becomes the ciphertext.
• Vernum Cipher- A method of encryption that uses a one-time pad (key) to create ciphertext that is mathematically impossible to decrypt.
• Key: in cryptography it is the data that is used to encrypt and decrypt the data.

One Time Pad

Each character in the plain text is combined with the character in the corresponding position in the key by converting them both to binary. (Originally 5 bit Baudot now ASCII/Unicode).

• Each message uses a different key.
• It is the only uncrackable cipher.
• Baudot code- a five digit character code that predates both ASCII and Unicode

• Railfence Cipher- a type of transposition cipher that encodes the message by splitting it over row.
• Route Cipher- A type of transposition cipher that encodes the message by placing it into a grid
• With this type of cipher, the letters of the message are transposed or rearranged to form an anagram. You must rearrange the letters according to a set pattern to make it possible to decrypt the message.

• If you were decrypting this message you would need to know that the key is that it has been split over two lines
• To decrypt it, you simply read it back by moving down and then up. You could use any combination of lines and line lengths.

• A variation is to put the message into a grid. This is called a route cipher
• For example, a message can be placed into a 6x3 grid. Reading down in columns from left to right will decrypt the message. Notice that you can add null or meaningless values if you have spare cells in your grid. In this case, the letter 'A' has been added to the bottom right hand cell.