HTTPS


Hypertext Transfer Protocol Secure is an extension of the Hypertext Transfer Protocol. It uses encryption for secure communication over a computer network, and is widely used on the Internet. In HTTPS, the communication protocol is encrypted using Transport Layer Security or, formerly, Secure Sockets Layer. The protocol is therefore also referred to as HTTP over TLS, or HTTP over SSL.
The principal motivations for HTTPS are authentication of the accessed website and protection of the privacy and integrity of the exchanged data while it is in transit. It protects against man-in-the-middle attacks, and the bidirectional block cipher encryption of communications between a client and server protects the communications against eavesdropping and tampering. The authentication aspect of HTTPS requires a trusted third party to sign server-side digital certificates. This was historically an expensive operation, which meant fully authenticated HTTPS connections were usually found only on secured payment transaction services and other secured corporate information systems on the World Wide Web. In 2016, a campaign by the Electronic Frontier Foundation with the support of web browser developers led to the protocol becoming more prevalent. HTTPS has since 2018 been used more often by web users than non-secure HTTP, primarily to protect page authenticity on all types of websites, secure accounts, and keep user communications, identity, and web browsing private.

Overview

The Uniform Resource Identifier scheme HTTPS has identical usage syntax to the HTTP scheme. However, HTTPS signals the browser to use an added encryption layer of SSL/TLS to protect the traffic. SSL/TLS is especially suited for HTTP, since it can provide some protection even if only one side of the communication is authenticated. This is the case with HTTP transactions over the Internet, where typically only the server is authenticated.
HTTPS creates a secure channel over an insecure network. This ensures reasonable protection from eavesdroppers and man-in-the-middle attacks, provided that adequate cipher suites are used and that the server certificate is verified and trusted.
Because HTTPS piggybacks HTTP entirely on top of TLS, the entirety of the underlying HTTP protocol can be encrypted. This includes the request's URL, query parameters, headers, and cookies. However, because website addresses and port numbers are necessarily part of the underlying TCP/IP protocols, HTTPS cannot protect their disclosure. In practice this means that even on a correctly configured web server, eavesdroppers can infer the IP address and port number of the web server, and sometimes even the domain name that a user is communicating with, along with the amount of data transferred and the duration of the communication, though not the content of the communication.
Web browsers know how to trust HTTPS websites based on certificate authorities that come pre-installed in their software. Certificate authorities are in this way being trusted by web browser creators to provide valid certificates. Therefore, a user should trust an HTTPS connection to a website if and only if all of the following are true:
  • The user trusts that their device, hosting the browser and the method to get the browser itself, is not compromised.
  • The user trusts that the browser software correctly implements HTTPS with correctly pre-installed certificate authorities.
  • The user trusts the certificate authority to vouch only for legitimate websites.
  • The website provides a valid certificate, which means it was signed by a trusted authority.
  • The certificate correctly identifies the website.
  • The user trusts that the protocol's encryption layer is sufficiently secure against eavesdroppers.
HTTPS is especially important over insecure networks and networks that may be subject to tampering. Insecure networks, such as public Wi-Fi access points, allow anyone on the same local network to packet-sniff and discover sensitive information not protected by HTTPS. Additionally, some free-to-use and paid WLAN networks have been observed tampering with webpages by engaging in packet injection in order to serve their own ads on other websites. This practice can be exploited maliciously in many ways, such as by injecting malware onto webpages and stealing users' private information.
HTTPS is also important for connections over the Tor network, as malicious Tor nodes could otherwise damage or alter the contents passing through them in an insecure fashion and inject malware into the connection. This is one reason why the Electronic Frontier Foundation and the Tor Project started the development of HTTPS Everywhere, which is included in Tor Browser.
As more information is revealed about global mass surveillance and criminals stealing personal information, the use of HTTPS security on all websites is becoming increasingly important regardless of the type of Internet connection being used. Even though metadata about individual pages that a user visits might not be considered sensitive, when aggregated it can reveal a lot about the user and compromise the user's privacy.
Deploying HTTPS also allows the use of HTTP/2 and HTTP/3, which are new HTTP versions designed to reduce page load times, size, and latency.
It is recommended to use HTTP Strict Transport Security with HTTPS to protect users from man-in-the-middle attacks, especially SSL stripping.
HTTPS should not be confused with the seldom-used Secure HTTP specified in RFC 2660.

Usage in websites

, 33.2% of Alexa top 1,000,000 websites use HTTPS as default and 70% of page loads use HTTPS., 71.2% of the Internet's 150,000 most popular websites have a secure implementation of HTTPS, However, despite TLS 1.3's release in 2018, adoption has been slow, with many still remaining on the older TLS 1.2 protocol.

Browser integration

Most browsers display a warning if they receive an invalid certificate. Older browsers, when connecting to a site with an invalid certificate, would present the user with a dialog box asking whether they wanted to continue. Newer browsers display a warning across the entire window. Newer browsers also prominently display the site's security information in the address bar. Extended validation certificates show the legal entity on the certificate information. Most browsers also display a warning to the user when visiting a site that contains a mixture of encrypted and unencrypted content. Additionally, many web filters return a security warning when visiting prohibited websites.
The Electronic Frontier Foundation, opining that "In an ideal world, every web request could be defaulted to HTTPS", has provided an add-on called HTTPS Everywhere for Mozilla Firefox, Google Chrome, Chromium, and Android, which enables HTTPS by default for hundreds of frequently used websites.
Forcing a web browser to load only HTTPS content has been supported in Firefox starting in version 83. Starting in version 94, Google Chrome is able to "always use secure connections" if toggled in the browser's settings.

Security

The security of HTTPS is that of the underlying TLS, which typically uses long-term public and private keys to generate a short-term session key, which is then used to encrypt the data flow between the client and the server. X.509 certificates are used to authenticate the server. As a consequence, certificate authorities and public key certificates are necessary to verify the relation between the certificate and its owner, as well as to generate, sign, and administer the validity of certificates. While this can be more beneficial than verifying the identities via a web of trust, the 2013 mass surveillance disclosures drew attention to certificate authorities as a potential weak point allowing man-in-the-middle attacks. An important property in this context is forward secrecy, which ensures that encrypted communications recorded in the past cannot be retrieved and decrypted should long-term secret keys or passwords be compromised in the future. Not all web servers provide forward secrecy.
For HTTPS to be effective, a site must be completely hosted over HTTPS. If some of the site's contents are loaded over HTTP, or if only a certain page that contains sensitive information, such as a log-in page, is loaded over HTTPS while the rest of the site is loaded over plain HTTP, the user will be vulnerable to attacks and surveillance. Additionally, cookies on a site served through HTTPS must have the secure attribute enabled. On a site that has sensitive information on it, the user and the session will get exposed every time that site is accessed with HTTP instead of HTTPS.

Technical

Difference from HTTP

HTTPS URLs begin with "https://" and use port 443 by default, whereas HTTP URLs begin with "http://" and use port 80 by default.
HTTP is not encrypted and thus is vulnerable to man-in-the-middle and eavesdropping attacks, which can let attackers gain access to website accounts and sensitive information, and modify webpages to inject malware or advertisements. HTTPS is designed to withstand such attacks and is considered secure against them.

Network layers

HTTP operates at the highest layer of the TCP/IP model—the application layer; as does the TLS security protocol, which encrypts an HTTP message prior to transmission and decrypts a message upon arrival. Strictly speaking, HTTPS is not a separate protocol, but refers to the use of ordinary HTTP over an encrypted SSL/TLS connection.
HTTPS encrypts all message contents, including the HTTP headers and the request/response data. With the exception of the possible CCA cryptographic attack described in the [|limitations] section below, an attacker should at most be able to discover that a connection is taking place between two parties, along with their domain names and IP addresses.