In TLS, forward secrecy is provided by choosing ciphersuites that include the DHE and ECDHE key exchanges. This means that even if the server’s base private key is compromised, an attacker can’t retroactively decrypt information. In forward secret connections, the server and client create a temporary key for every new session that gets effectively “thrown away” after the session is complete. In non-forward-secret HTTPS connections, if an attacker records encrypted traffic between a website and its visitors, and later obtains the website’s private key, that key can be used to decrypt all past recorded traffic. is configured to support TLSv1.0, TLSv1.1, and TLSv1.2, and has TLS Fallback SCSV enabled.įorward secrecy protects information sent over an encrypted HTTPS connection now from being decrypted later, even if the server’s private key is later compromised.gov domains will note when a domain still offers insecure SSLv3, or when a domain does not yet offer TLSv1.2. It is possible for an attacker to interfere with the negotiation process and attempt to “downgrade” connections to the oldest mutually supported version.Ī downgrade attack can be prevented by using TLS Fallback SCSV, a TLS extension proposed in 2014 and which is enabled by default in newer versions of OpenSSL.įor more details of NIST recommendations, read NIST Special Publication 800-52. Typically, browsers and servers support multiple versions, and will attempt to negotiate the strongest mutually supported version. This is the strongest form of TLS today, and is widely supported by modern browsers. An improvement over TLSv1.0, but was quickly superseded by TLSv1.2. NIST Special Publication 800-52 disallows TLSv1.0 for government-facing systems. Used widely today to support some older clients, like IE8 and Android 4.3 and below. Turning off SSLv3 effectively removes support for Internet Explorer 6. Considered to be insecure after the POODLE attack was published in 2014. The major versions of SSL/TLS in use today are: However, all versions of SSL as a protocol are now considered insecure for modern use. Because of its early ubiquity, “SSL” is frequently used today to generically refer to TLS/HTTPS. SSL and TLS perform the same function, and TLS is a direct successor and replacement for SSL. TLS is a network protocol that establishes an encrypted connection to an authenticated peer over an untrusted network.Įarlier, less secure versions of this protocol were called Secure Sockets Layer, or SSL). HTTPS today uses Transport Layer Security, or TLS. Signature algorithms, such as SHA-1 and SHA-2.This page covers some relevant technical concepts relevant to the strength and quality of a server’s HTTPS configuration.
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