Encryption: Public Key and Private Key

A popular technic for encrypting messages sent between two users is the asymmetric key encryption scheme. The main aspects of this scheme is the use of public and private keys to utilize the encryption between sender and receiver. Two keys are present for the sender/receiver and these are unique and as the names of the keys suggests there is one Private key and one Public Key. The Public key is public to the entire world whereas the Private Key is kept hidden and confidential as anyone in possession of the private is capable of decryption the messages encrypted by the corresponding public key and thereby reading the messages in plain text.

The two keys are mathematically related and any message encrypted with a public key, may only be decrypted by it's corresponding private key.

• Public Key  

The public key is used to encrypt messages and as mentioned above it is public for anyone to read and see, this is do to it being the one used to make a message sent to you encrypted.

• Private Key

The Private Key is used to decrypt messages. It is therefor kept confidential at a place reachable from where the encrypted message is received. If you for example gets files sent to you locally the key can be kept on your local computer, but if you for example use it as part of a distributed system then the private key is most likely placed on a remote server alongside the system in an area which is cut off from public view through the Internet.

Use Case:

To understand how asymmetric key encryption scheme is used in a real world situation the following Use Case will illustrate how Lisa and Tom is sending encrypted messages to each other.