Transport Layer Security |
Secure Sockets Layer (SSL) and Transport Layer Security (TLS), its successor, are cryptographic protocols which provide security communications on the Internet. There are slight differences between SSL 3.0 and TLS 1.0, but the protocol remains substantially the same. The term SSL as used here applies to both protocols unless clarified by context.
=Description=
SSL provides endpoint authentication and information security over the Internet using Cryptography. In typical use, only the server is authenticated (i.e. its identity is ensured) while the client remains unauthenticated; mutual authentication requires Public key infrastructure deployment to clients. The protocols allow client/server applications to communicate in a way designed to prevent eavesdropping, tampering, and message forgery. SSL involves a number of basic phases:
During the first phase, the client and server negotiate which cryptographic algorithms will be used. Current implementations support the following choices:
=How it works=
The SSL protocol exchanges records; each record can be optionally compressed, encrypted and packed with a Message authentication code (Message Authentication Code). Each record has a content_type field that specifies which upper level protocol is being used.
When the connection starts, the record level encapsulates another protocol, the handshake protocol, which has content_type 22.
The client sends and receives several handshake structures:
TLS has a variety of security measures:
=Applications=
SSL runs on layers beneath application protocols such as HTTP, SMTP and Network News Transfer Protocol and above the Transmission Control Protocol transport protocol, which forms part of the Internet protocol suite protocol suite. While it can add security to any protocol that uses reliable connections (such as TCP), it is most commonly used with HTTP to form HTTPS. HTTPS is used to secure World Wide Web pages for applications such as electronic commerce. It uses public key certificates to verify the identity of endpoints.
While an increasing number of client and server products can support SSL natively, many still do not. In these cases, a user may wish to use standalone SSL products like Stunnel to provide encryption. However, the IETF recommended in 1997 that application protocols offer a way to upgrade to TLS from a plaintext connection, rather than use a separate port for encrypted communications - this prevents use of wrappers such as Stunnel.
SSL can also be used to tunnel an entire network stack to create a Virtual Private Network, as is the case with OpenVPN.
=History and development=
Developed by Netscape Communications Corporation, SSL version 3.0 was released in 1996, which later served as a basis to develop TLS version 1.0, an IETF standard protocol first defined in RFC 2246. Visa, MasterCard, American Express and many leading financial institutions have endorsed SSL for commerce over the Internet.
SSL operates in modular fashion: its authors designed it for extendability, with support for forwards and backwards compatibility and negotiation between peer-to-peers.
==Early weak keys==
Some early implementations of SSL could use a maximum of only 40-bit encryption symmetric keys because of United States of America government restrictions on the Export of cryptography. The US government explicitly imposed a 40-bit keyspace small enough to be broken by brute-force search by law enforcement agencies wishing to read the encrypted traffic, while still presenting obstacles to less-well-funded attackers. A similar limitation applied to Lotus Notes in export versions. After several years of public controversy, a series of lawsuits, and eventual US government recognition of changes in the market availability of better cryptographic products produced outside the US, the authorities relaxed some aspects of the export restrictions. The 40-bit key size limitation has mostly gone away. Modern implementations use 128-bit (or longer) keys for symmetric key ciphers.
=Standards=
The first definition of TLS appeared in RFC 2246: The TLS Protocol Version 1.0 .
Other Request for commentss subsequently extended TLS, including:
=TLS 1.1=
TLS 1.1 is the next generation of the TLS protocol. TLS 1.1 is currently a draft and is expected to be published as RFC late 2005. A Last Call , one of the last steps in the RFC process, was issued August 19, 2004. TLS 1.1 clarifies some ambiguities and adds a number of recommendations. TLS 1.1 is very similar to TLS 1.0. Main reason for the new version number is a modified format for the encrypted packages, which is done to protect against a certain form of attack. TLS 1.1 is currently supported by Opera_(web_browser) and GnuTLS.
= See also =
= External links =
=References=
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