Crypto U12, SSL

Crypto U12, SSL

1. background

   • sits on top of TCP
     • roughly equivalent to TLS
   • created by IETF
     • Internet Engineering Task Force

2. design

   • designed for open environments where entities do not have a security association
     • security association: having some relationship where communicating entities have agreed or exchanged security related info or cryptographic keys
   • security requirements
     • confidentiality
     • data origin authentication
     • entity authentication
   • can provide 2 types of authentication
     • client only
     • mutual entitiy
   • minimalizes public key operations
   • decryption of public key message is placed at the server and saves work for the client

3. crypotgraphic primitives: uses hybrid encryption

   • public key cryptography
     • enables symmetric key establishment
   • digital signatures
     • sign certificates and facilitate entity authentication
   • MACs
     • used to provide data origin authentication and entity authentication
   • hash functions
     • part of MACs, digital signatures, key derivation

4. algorithms used

   • Flexible standard. Supports many different algorithms and key lengths.
     • during exchange, entities agree upon a "cipher suite"
       • cipher suite - collection of algorithms that communicating entities agree upon
   • common
     • AES in CBC mode
     • HMAC using SHA-256
     • digital signature algorithms
       • RSA
       • DSA

5. protocols used

   • handshake
     • extablish agreements appropriate to secure communication
       • agree upon cipher suite
       • extablish entitity authentication
       • establish keys for secure channel
     • sometimes mutual entity authentication is needed in closed systems. basic handshake protocol does not provide this.
       • so, a "modified handshake protocol" can be used
   • record
     • implements secure channel

6. security issues

   • will not work if process failures
     • ex: client does not perform PKCS checks
   • implementation failures
     • relies on many cryptographic primitives
   • key mgt failures
   • usage failures
     • security features overestimated and gain a false sense of security

7. key management

   • generation
     • asymmetric keys
       • through PKMS
     • symmetric keys
       • derived from master secret
       • lightweight
       • allows many keys to be generated
       • reliant on client's ability to generate a random pre-master secret
   • establishment
     • pre-master key shared through public key encryption
   • storage
     • private keys must be stored in safe place
     • very sensitive, but short-lived
   • usage
     • key separation enforced
     • separate keys for communication between client & server and server & client
       • prevents reflection attacks