Key Exchange
Key exchange is any method by which cryptographic keys are transferred among users, thus enabling the use of a cryptographic algorithm.
- allows two hosts to know the same symmetric encryption key without any other host finding out what it is
- A symmetric cipher is often used to protect the actual data exchange in a session
- Asymmetric encryption is used to encrypt and exchange symmetric cipher keys
- how it works
- sender uses the recipient’s public key to encrypt a secret key
- recipient uses the private key to retrieve the secret key
- then uses the secret key to decrypt whatever data message was transmitted by the sender
- the symmetric cipher secret key is also referred to as a session key
- if it is often changed, then its known as an ephemeral key