channel security
Summary
Station-to-station(STS)
- AKE
- uses diffie-hellman key exchange + signatures
- achieves forward secrecy
PKC-based
- AKE
- uses RSA
Secure channel
- encrypt-and-mac using session key
- ensures confidentiality and integrity
Transport Layer Security(TLS)
- successor to Secure Socket Layer(SSL)
- foundation for Hypertext Transfer Protocol(Secured) (HTTPS)
Forward secrecy
- past session keys remain safe even if long-term private key leaks later
- older ciphertexts are protected even in the future
Concept
Challenge-response
- symmetric, shared secret
- uses keyed hash
Unilateral authentication
- authenticates the client, in this example
- uses signature
requires a homomorphic asymmetric encryption scheme such as RSA
Key exchange
- establish a shared session key over an unsecured channel
- session key can then be used for symmetric encryption
- eg. PKC-based, diffie-hellman key exchange
Man-in-the-middle
- client is not necessarily authenticated during key exchange
- Mallory can create a session key for each user, sniffing/spoofing the communication between them
Authenticated key exchange(AKE)
- authentication + key exchange
- prevents man-in-the-middle attack
- eg. PKC-based, STS