Brief-on encryption and decryption

Data protection, the need for information security

It is often required to transfer sensitive information of personal, financial or business nature. In these instances we want to ensure that this information is delivered securely and to the correct person. Physical delivery is more often impossible so electronic means are used. In this case, the transmissions are susceptible to eavesdropping (someone looking at the data) or interception (someone ‘getting’ the data) and/or alteration (someone changing the data). To counter these possible attacks encryption is used so that it is extremely difficult for intruders to see or get the data and even if they manage to see or capture it, they will not be able to understand it.

Encryption and decryption

Encryption is the process of converting information or data to some code or cipher which prohibits unauthorised access. There exists various algorithms of this conversion. The common elements of a conversion process are: 1) the data (also referred to as the plain text), 2) a secret value (referred to as the key or password), 3) an encryption algorithm (for the conversion from plain text to cipher) 4) the incomprehensible text (or cipher) and 5) the decryption algorithm (for the conversion of cipher back to original plain text.

Types of encryption

Encryption can be symmetric when the key (secret value) used for encryption is the same as the one used for decryption. This usually means that sender and recipient will have to somehow share the key or have previously agreed on it.

Encryption can be asymmetric when one key is used for encryption and a different value is used for decryption. This type of encryption is also known as public-key encryption because of the approach followed for the encryption/decryption.

Encryption for authentication

When using public-key encryption it can also act as an authentication to ensure that the sender of the message is actually who they say they are. Consider that Bob wants to send some information to Sue. The information is not sensitive but Sue must get it and be certain that the information is valid and coming from Bob.
Bob can use his private key to encrypt the plain text and then send the cipher to Sue. When Sue receives the cipher, the only way to see the message is to decrypt it using Bob’s public key. This means that the message can only have been send from Bob as he is the only one having Bob’s private key (which can only be decrypted using Bob’s public key).

Download the  brief-on encryption and decryption  file which includes the text above and some examples.