A digital key is a numeric value (not a physical key) which may be used to encrypt, decrypt, or digitally sign messages or data. Encryption is changing the data to a secret form where a thrid party should not be able to read it. Decryption is the process of changing the encrypted data back into a readable or plaintext form. Digitally signing messages provides proof that the person who claims to have sent the message actually sent it.
There are several types of digital key systems including:
- symmetric key system - A single key is generated and is used to encrypt or decrypt data. The single key is usually shared between two people so they can pass secret messages between each other.
- Assymetric key - A public and private key is generated. The public key and private key are mathematically related but it is very difficult or impossible for the private key to be discovered using the public key. The public key can be given to anyone and the private key must be kept secret. There are two main uses for this type of a key system. These are.
- To allow anyone to pass a secret message to one person who holds the private key. This method provides confidentiality.
- To allow someone to send a message that they can prove they have sent. This method provides sender authentication.