Difference between https protocol and SSL Certificate

What is difference between https protocol and SSL Certificate that we use in web browser?

Aren't both of these used to encrypt communication between client (browser) and server?

HTTPS is HTTP (HyperText Transfer Protocol) plus SSL (Secure Socket Layer). You need a certificate to use any protocol that uses SSL.

SSL allows arbitrary protocols to be communicated securely. It enables clients to (a) verify that they are indeed communicating with the server they expect and not a man-in-the-middle and (b) encrypt the network traffic so that parties other than the client and server cannot see the communication.

An SSL certificate contains a public key and certificate issuer. Not only can clients use the certificate to communicate with a server, clients can verify that the certificate was cryptographically signed by an official Certificate Authority. For example, if your browser trusts the VeriSign Certificate Authority, and VeriSign signs my SSL certificate, your browser will inherently trust my SSL certificate.

There's some good reading here: http://en.wikipedia.org/wiki/Transport_Layer_Security

Two pieces of one solution.

https is the protocol that defines how the client and server are going to negotiate a secure connection.

The SSL Certificate is the document that they will use to agree upon the servers authenticity.

HTPS is the new HTTPS. HTTPS is highly vulnerable to SSL Stripping / MITM (man in the middle). to quote adam langley's (google) blog imperial violet:

"HTTPS tends to cause people to give talks mocking certificate security and the ecosystem around it. "

The problem is that the page isn't served over HTTPS. It should have been, but when a user types a hostname into a browser, the default scheme is HTTP. The server may attempt to redirect users to HTTPS, but that redirect is insecure: a MITM attacker can rewrite it and keep the user on HTTP, spoofing the real site the whole time. The attacker can now intercept all the traffic to this perfectly well configured and secure website.

This is called SSL stripping and it's terribly simple and devastatingly effective. We probably don't see it very often because it's not something that corporate proxies need to do, so it's not in off-the-shelf devices. But that respite is unlikely to last very long and maybe it's already over: how would we even know if it was being used?

In order to stop SSL stripping, we need to make HTTPS the only protocol. We can't do that for the whole Internet, but we can do it site-by-site with HTTP Strict Transport Security (HSTS).

HSTS tells browsers to always make requests over HTTPS to HSTS sites. Sites become HSTS either by being built into the browser, or by advertising a header:

Strict-Transport-Security: max-age=8640000; includeSubDomains

The header is in force for the given number of seconds and may also apply to all subdomains. The header must be received over a clean HTTPS connection.

Once the browser knows that a site is HTTPS only, the user typing mail.google.com is safe: the initial request uses HTTPS and there's no hole for an attacker to exploit.

(mail.google.com and a number of other sites are already built into Chrome as HSTS sites so it's not actually possible to access accounts.google.com over HTTP with Chrome - I had to doctor that image! If you want to be included in Chrome's built-in HSTS list, email me.)

HSTS can also protect you, the webmaster, from making silly mistakes. Let's assume that you've told your mother that she should always type https:// before going to her banking site or maybe you setup a bookmark for her. That's honestly more than we can, or should, expect of our users. But let's say that our supererogatory user... ]

because of obstructing/very stupid link-rules for new users on stackoverflow i cannot give you the rest of adam's answer and you'll have to visit adam langley's blog yourself at https://www.imperialviolet.org/2012/07/19/hope9talk.html

"Adam Langley works on both Google's HTTPS serving infrastructure and Google Chrome's network stack."

HTTPS is an application layer protocol. It can provide non-repudiation of individual requests or responses through digital signatures.

SSL is a lower level protocol and does not have this capability. SSL is a transport level encryption.

HTTPS is more flexible than SSL: an application can configure the level of security it needs. SSL has fewer options so it is easier to setup and administer.