Encryption

• A Wi-Fi password known as a pre-shared key (PSK) is given to each user that wants to connect to the network. The data is then encrypted using this key: symmetric encryption.
• Sensitive data is often transmitted via the Internet which is a public network.
• Data is stored on computers and servers on the Internet which may be hacked.
• The purpose of encryption is to encode a file or data into something that cannot be read or understood.
• The file or data that cannot be understood is known as encrypted. A key or password is used to decrypt the data.
• In symmetric encryption, a key is first shared between the sender and receiver.

  • This key encrypts the data before it is transmitted.
  • The receiver uses the key to decrypt the data.
• Uses for symmetric encryption:

  • Adding a password to a ZIP file which also encrypts the file.
  • Encrypting a hard drive or external storage device.
• In asymmetric encryption, two keys are created by the receiver.

  • The public key is accessible by anyone and used to encrypt data.
  • The private key is kept secret by the receiver and used to decrypt the data.
• Asymmetric encryption is also known as public-key cryptography.
• In asymmetric encryption there is no need to share a secret key as happens with symmetric encryption.
• Symmetric encryption diagram:

  A) sender

  B) receiver

  C) plaintext

  D) encrypted text

  E) plaintext

  F) secret shared key

  G) secret shared key

  
• Asymmetric encryption diagram:

  A) sender

  B) receiver

  C) plaintext

  D) encrypted text

  E) plaintext

  F) public key

  G) private key

  
• In asymmetric encryption both keys are generated by the receiver. Only the public key is shared with the sender.
• Web pages that are shared using HTTPS use asymmetric encryption. The browser and server share the necessary public keys to encrypt the data. They then use their private keys to decrypt the data.
• If symmetric encryption were used in websites, every website you visit would first need to send the password privately to you.
• In Caesar cipher the alphabets are displaced by a known amount.
• Disadvantages of Caesar cipher:

  • Can be easily cracked by unintended users.
  • Cannot be used for highly confidential information.
• In reverse cipher, the message is encrypted by reversing it. This encoding is very simple and easy to crack by an attacker.
• In reverse cipher, the spacing can be removed to make the ciphertext harder to crack. The letters may also be grouped differently.
• Using reverse cipher on a message and then using Caesar cipher would make the text almost unreadable.
• A substitution cipher denotes encryption algorithms wherein each character is replaced by another character.
• Pigpen cipher, Caesar cipher and modulo 2 encoding are substitutional ciphers.
• In the pigpen cipher, alphabets are placed in grids. The characters are encrypted using the shape of the section of the grid it represents.
• In modulo 2 encoding, five-bit binary codes are assigned to all alphabets. Out of the 26 letters, an alphabet letter is chosen to be the key. To encrypt a letter, its binary code is added to the binary code of the key letter.
• The process used in Modulo-2 encoding can be called modulo-2 addition or binary XOR operation.
• Transposition cipher is a form of encryption in which the plaintext is rearranged in a new order to form ciphertext.
• Two types of transposition ciphers:

  1. Rail fence method.
  2. Route method.
• Rail fence method:

  • The characters in a message are written on several lines and then, characters are combined line by line to form ciphertext.
• Route method:

  • Characters are placed in a grid column by column.
  • The sender can enter any value to blank grids. The ciphertext is obtained by writing the characters row by row.
• In the XOR function, the output is 1 only when both the inputs are different. When both the inputs are the same, the output is 0.
• Validation is the process of checking that the data is reasonable or falls within certain parameters.