Editing Transport Layer Security (section)

====Resumed TLS handshake====
Public key operations (e.g., RSA) are relatively expensive in terms of computational power. TLS provides a secure shortcut in the handshake mechanism to avoid these operations: resumed sessions. Resumed sessions are implemented using session IDs or session tickets.

Apart from the performance benefit, resumed sessions can also be used for [[single sign-on]], as it guarantees that both the original session and any resumed session originate from the same client. This is of particular importance for the [[FTPS|FTP over TLS/SSL]] protocol, which would otherwise suffer from a man-in-the-middle attack in which an attacker could intercept the contents of the secondary data connections.<ref>{{cite web|author=Chris|url=http://scarybeastsecurity.blogspot.com/2009/02/vsftpd-210-released.html|title=vsftpd-2.1.0 released – Using TLS session resume for FTPS data connection authentication|publisher=Scarybeastsecurity. blogspot.com|date=2009-02-18|access-date=2012-05-17|url-status=live|archive-url=https://web.archive.org/web/20120707213409/http://scarybeastsecurity.blogspot.com/2009/02/vsftpd-210-released.html|archive-date=2012-07-07}}</ref>