Cipher suite rollback: a misuse pattern for the SSL/TLS client/server authentication handshake protocol
Ali Alkazimi, Eduardo B. Fernández · 2014
Transport Layer Security (TLS) is a cryptographic protocol that provides a secure channel between a client and a server. TLS is the successor to the Secure Sockets Layer (SSL) protocol. The secure connection prevents an attacker from eavesdropping an established client-server connection. It is used in most internet communications for enabling secure web browsing. The SSL/TLS security protocol is layered between the application protocol layer and the TCP/IP layer and includes as one of its sub-protocols the Handshake Protocol. We present here a misuse pattern for the SSL/TLS Handshake Protocol: the Cipher Suite Rollback, where the attacker intercepts the ClientHello message, replaces the CipherSuite (a list of encryption algorithms), with a weak or NULL-Cipher, and passes the intercepted message to the server which will now use a weaker cipher, allowing the attacker to gain access to the exchanged data between the client and the server.