1. Presentation on :
Transport Layer Security
(TLS)
Presented by : Chhatra Thapa
2. Two protocols are dominant today for providing
security at the transport layer
Secure Sockets Layer (SSL) protocol
Transport Layer Security (TLS) protocol
3. Definition:
Transport Layer Security (TLS) was designed to
provide security at the transport layer.
TLS was derived from a security protocol called
Secure Sockets Layer (SSL).
The first difference is the version number (major and minor). The current version of SSL is 3.0; the current version of TLS is 1.0. In other words, SSLv3.0 is compatible with TLSv1.0.Another minor difference between SSL and TLS is the lack of support for the Fortezza method. TLS does not support Fortezza for key exchange or for encryption/decryption. “standardized” by IETF RFC2246.
End-to-end between a client and server – Sits on top of TCP – Requires reliable connectionMost important Internet crypto protocol? – Secure web pages – E-mail and LDAP access control
Handshake: Responsible for negotiating security, authenticating the server to the browser, and (optionally) defining other communication parameters.Data exchange (record) protocol uses the secret key to encrypt the data for secrecy and to encrypt the message digest for integrity.Phase 1 : Client sideversion, client random number, session id , compression method Server sideVersion, server random number, session, selected compression methodAfter Phase I, the client and server know the following:The version of SSL❏ The algorithms for key exchange, message authentication, and encryption❏ The compression method❏ The two random numbers for key generationPhase 2: After Phase II,❏ The server is authenticated to the client.❏ The client knows the public key of the server if required.Server sends a certificate message that includes the public key of the server. The public key is certified by some certification authority, which means that the public key is encrypted by a CA private key. Browser has a list of CAs and their public keys. It uses the corresponding key to decrypt the certification and finds the server public key. This also authenticates the server because the public key is certified by the CA.Phase 3: After Phase III,❏ The client is authenticated for the server.❏ Both the client and the server know the pre-master secret.Browser sends a secret key, encrypts it with the server public key, and sends it to the server.Phase 4:After Phase IV, the client and server are ready to exchange data.Browser sends a message, encrypted by the secret key, to inform the server that handshaking is terminating from the browser key.Server decrypts the secret key using it private key and decrypts the message using the secret key. It then sends a message, encrypted by the secret key, to inform the browser that handshaking is terminating from the server side.
TLS supports all of the alerts defined in SSL except for NoCertificate. TLS also adds some new ones to the list. Table shows the full list of alerts supported by TLS.
