The open incarnation of SSL. SSL (Secure Socket Layer) was the original encryption for web sessions, TLS (Transport Layer Security) does exactly the same thing but is open source.
You use one or the other whenever you use https instead of http to access a web page. When a web page tells you it is going to send you to a "secure server", it's sending you to something that uses one or the other. Whether or not you had to login (authenticate), everything transmitted over these protocols is encrypted.
If you have a Linux or other modern Unix machine, you have the "openssl" command which, in addition to what it was wriiten to do, can also help help you debug ssl connections. For example:
openssl s_client -connect 10.1.36.237:995 CONNECTED(00000003) depth=0 /CN=fmail/OU=foo/O=foo.org/L=sharon/ST=ma/C=US verify error:num=18:self signed certificate verify return:1 depth=0 /CN=fmail/OU=foo/O=foo.org/L=sharon/ST=ma/C=US verify return:1 --- Certificate chain 0 s:/CN=fmail/OU=foo/O=foo.org/L=sharon/ST=ma/C=US i:/CN=fmail/OU=foo/O=foo.org/L=sharon/ST=ma/C=US --- Server certificate -----BEGIN CERTIFICATE----- (ssl certificate displayed here) -----END CERTIFICATE----- subject=/CN=fmail/OU=foo/O=foo.org/L=sharon/ST=ma/C=US issuer=/CN=fmail/OU=foo/O=foo.org/L=sharon/ST=ma/C=US --- No client certificate CA names sent --- SSL handshake has read 748 bytes and written 340 bytes --- New, TLSv1/SSLv3, Cipher is AES256-SHA Server public key is 1024 bit SSL-Session: Protocol : TLSv1 Cipher : AES256-SHA Session-ID: 6E9E151BBF66A3AF63218459D568504534DAFF9C84588CF87C963C7FD8C7B092 Session-ID-ctx: Master-Key: DC4891E43C5D1F48CA8F2F3E39171DE331CCA6D6163654AFA2F071B77E9C91D12031B789AF559D8E63A5CD2D3A20957F Key-Arg : None Start Time: 1101221734 Timeout : 300 (sec) Verify return code: 18 (self signed certificate) --- +OK Foo MailServer POP3 server ready <6252.1101221735@fmail> user tonyfoo +OK please send PASS command pass ********* +OK 0 messages (0 octets) quit +OK POP3 server signing off closed
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