Computer Science : S2 : L5 : Encryption

Encryption alters data into a dorm that is unreadable by anyone for whom the data is not intended. It cannot prevent the data being intercepted but makes the data unreadable to the unwanted access.

First form was the caesar cipher; this is when a letter is replaced by another letter from a fixed distance. The aim of encryption is to make the origin message impossible to crack. Shift Cipher is a movement or a shift in x places.

Plain text is the original data , once it is encrypted it then becomes ciphertext. When it gets to the receiving end it stays in cipher text until it is decrypt and becomes plain text again.

Methods of encryption : 

• Symmetric encryption

Symmetric encryption is when you have one key to encrypt and decrypt the data. When communicating the sending parties will both need the same key so they can encrypt and decrypt the data. It only works if the key is kept secret. Symmetric encryption is smoother and faster and is good for large data however the cons is the key needs to be kept secret otherwise it will be decrypted by unwanted people. (Is not as secure an not good for sensitive data)

• Asymmetric encryption

Asymmetric encryption is when to encrypt and decrypt you use a public and private key, data encrypted with a public key can only be decrypted with a private key.( Good for small shorter  distances and is more complex so is used to transport sensitive data ) (The private and public key come as a pair)

It works by both having a public and private key, the sender and recipient exchange their public keys. To use it the sender will use the recipient's public key to send data to the recipient the recipient will then use their own private key to decrypt the data. You can use it the other way by using the private key to encrypt the message. You know the information has to come from the sender because only they have their own private key.

Combined Encryption is when the sender uses their private key and the recipient's public key to create a combined encryption key. The recipient must use their own private key and the sender's public key. This means you know the message is authentic and that the message has not been modified.