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Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocol
Cryptographic protocol

A security protocol is an abstract or concrete protocol that performs a information security-related function and applies cryptographic methods....
s that provide security
Security

Security is the degree of protection against danger, loss, and criminals. Individuals or actions that encroach upon the condition of protection are responsible for a "breach of security."...
 and data integrity
Data integrity

Data integrity is a term used in computer science and telecommunications that can mean ensuring data is "whole" or complete, the condition in which data are identically maintained during any operation , the preservation of data for their intended use, or, relative to specified operations, the a priori expectation of data quality....
 for communications over TCP/IP
Internet protocol suite

The Internet Protocol Suite is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol and the Internet Protocol , which were the first two networking protocols defined in this standard....
 networks such as the Internet
Internet

The Internet is a global network of interconnected computers, enabling users to share information along multiple channels. Typically, a computer that connects to the Internet can access information from a vast array of available server and other computers by moving information from them to the computer's local memory....
. TLS and SSL encrypt the segments of network connections at the Transport Layer
Transport layer

In computer networking, the Transport Layer is a group of methods and protocols within a layered architecture of network components, within which it is responsible for encapsulating application data blocks into datagrams suitable for transfer to the network infrastructure for transmission to the destination host, or managing the reverse tran...
 end-to-end.

Several versions of the protocols are in wide-spread use in applications like web browsing, electronic mail
E-mail

Electronic mail, often abbreviated as e-mail, email, E-Mail, or eMail, is any method of creating, transmitting, or storing primarily text-based human communications with digital communications systems....
, Internet fax
Internet fax

Internet fax uses the internet to receive and send faxes.Internet faxing is a general term which refers to sending a document facsimile using the Internet, rather than using only phone networks ....
ing, instant messaging
Instant messaging

Instant messaging is a form of Real-time computing communication between two or more people based on typed text. The Written language is conveyed via devices connected over a network such as the Internet....
 and voice-over-IP (VoIP).

TLS is an IETF
Internet Engineering Task Force

The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the World Wide Web Consortium and International Organization for Standardization/International Electrotechnical Commission standard bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite....
 standards track
Internet standard

In computer network engineering, an Internet Standard is a normative specification of a technology or methodology applicable to the Internet. Internet Standards are created and published by the Internet Engineering Task Force ....
 protocol, last updated in RFC 5246, that was based on the earlier SSL specifications developed by Netscape
Netscape

Netscape Communications is a United States computer services company, best known for its web browser. The browser was once dominant in terms of Usage share of web browsers, but lost most of that share to Internet Explorer during the browser wars....
 Corporation.

TLS protocol allows client/server applications to communicate across a network in a way designed to prevent eavesdropping
Eavesdropping

Eavesdropping is the act of surreptitiously listening to a private conversation. This is commonly thought to be unethical and there is an old adage that eavesdroppers seldom hear anything good of themselves....
, tampering, and message forgery
Message forgery

In cryptography, message forgery is the sending of a message to deceive the recipient as to whom the real sender is. A common example is sending a e-mail spam e-mail as if it were originated from an address other than the one which was really used....
.






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Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocol
Cryptographic protocol

A security protocol is an abstract or concrete protocol that performs a information security-related function and applies cryptographic methods....
s that provide security
Security

Security is the degree of protection against danger, loss, and criminals. Individuals or actions that encroach upon the condition of protection are responsible for a "breach of security."...
 and data integrity
Data integrity

Data integrity is a term used in computer science and telecommunications that can mean ensuring data is "whole" or complete, the condition in which data are identically maintained during any operation , the preservation of data for their intended use, or, relative to specified operations, the a priori expectation of data quality....
 for communications over TCP/IP
Internet protocol suite

The Internet Protocol Suite is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol and the Internet Protocol , which were the first two networking protocols defined in this standard....
 networks such as the Internet
Internet

The Internet is a global network of interconnected computers, enabling users to share information along multiple channels. Typically, a computer that connects to the Internet can access information from a vast array of available server and other computers by moving information from them to the computer's local memory....
. TLS and SSL encrypt the segments of network connections at the Transport Layer
Transport layer

In computer networking, the Transport Layer is a group of methods and protocols within a layered architecture of network components, within which it is responsible for encapsulating application data blocks into datagrams suitable for transfer to the network infrastructure for transmission to the destination host, or managing the reverse tran...
 end-to-end.

Several versions of the protocols are in wide-spread use in applications like web browsing, electronic mail
E-mail

Electronic mail, often abbreviated as e-mail, email, E-Mail, or eMail, is any method of creating, transmitting, or storing primarily text-based human communications with digital communications systems....
, Internet fax
Internet fax

Internet fax uses the internet to receive and send faxes.Internet faxing is a general term which refers to sending a document facsimile using the Internet, rather than using only phone networks ....
ing, instant messaging
Instant messaging

Instant messaging is a form of Real-time computing communication between two or more people based on typed text. The Written language is conveyed via devices connected over a network such as the Internet....
 and voice-over-IP (VoIP).

TLS is an IETF
Internet Engineering Task Force

The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the World Wide Web Consortium and International Organization for Standardization/International Electrotechnical Commission standard bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite....
 standards track
Internet standard

In computer network engineering, an Internet Standard is a normative specification of a technology or methodology applicable to the Internet. Internet Standards are created and published by the Internet Engineering Task Force ....
 protocol, last updated in RFC 5246, that was based on the earlier SSL specifications developed by Netscape
Netscape

Netscape Communications is a United States computer services company, best known for its web browser. The browser was once dominant in terms of Usage share of web browsers, but lost most of that share to Internet Explorer during the browser wars....
 Corporation.

Description

The TLS protocol allows client/server applications to communicate across a network in a way designed to prevent eavesdropping
Eavesdropping

Eavesdropping is the act of surreptitiously listening to a private conversation. This is commonly thought to be unethical and there is an old adage that eavesdroppers seldom hear anything good of themselves....
, tampering, and message forgery
Message forgery

In cryptography, message forgery is the sending of a message to deceive the recipient as to whom the real sender is. A common example is sending a e-mail spam e-mail as if it were originated from an address other than the one which was really used....
. TLS provides endpoint authentication
Authentication

Authentication is the act of establishing or confirming something as authentic, that is, that claims made by or about the subject are true....
 and communications confidentiality
Information security

Information security means protecting information and information systems from unauthorized access, use, disclosure, disruption, modification or destruction....
 over the Internet
Internet

The Internet is a global network of interconnected computers, enabling users to share information along multiple channels. Typically, a computer that connects to the Internet can access information from a vast array of available server and other computers by moving information from them to the computer's local memory....
 using cryptography
Cryptography

Cryptography is the practice and study of hiding information. In modern times cryptography is considered a branch of both mathematics and computer science and is affiliated closely with information theory, computer security and engineering....
.

In typical end-user/browser usage, TLS authentication is unilateral: only the server is authenticated (the client knows the server's identity), but not vice versa (the client remains unauthenticated or anonymous). More strictly speaking, server authentication means different things to the browser (software) and to the end-user (human). At the browser level, it only means that the browser has validated the server's certificate — i.e., checked the digital signatures of the server certificate's issuing CA-chain (chain of Certification Authorities that guarantee bindings of identification information to public keys — see public key infrastructure
Public key infrastructure

The Public Key Infrastructure is a set of hardware, software, people, policies, and procedures needed to create, manage, store, distribute, and revoke digital certificates ....
). Once validated, the browser is justified in displaying a security icon (such as "closed padlock"). But mere validation does NOT "identify" the server to the end-user. For true identification, it is incumbent on the end-user to be diligent in scrutinizing the identification information contained in the server's certificate (and indeed its whole issuing CA-chain). This is the only way for the end-user to know the "identity" of the server. In particular: the "locked padlock" icon has no relationship to the URL, DNS name or IP address of the server. This is a common misconception. Such a binding can only be securely established if the URL, name or address is specified in the server's certificate itself. Malicious websites can't use the valid certificate of another website because they have no means to encrypt the transmission such that it can be decrypted with the valid certificate. Since only a trusted CA can embed a URL in the certificate, this ensures that checking the apparent URL with the URL specified in the certificate is a valid way of identifying the true site. Understanding this subtlety makes it very difficult for end-users to properly assess the security of web browsing (though this is not a shortcoming of the TLS protocol itself — it's a shortcoming of PKI).

TLS also supports the more secure bilateral connection mode (typically used in enterprise applications), in which both ends of the "conversation" can be ensured with whom they are communicating (provided they diligently scrutinize the identity information in the other party's certificate). This is known as mutual authentication
Mutual authentication

Mutual authentication or two-way authentication refers to two parties authenticating each other suitably. In technology terms, it refers to a client or user authenticating themselves to a server and that server authenticating itself to the user in such a way that both parties are assured of the others' identity....
. Mutual authentication requires that the TLS client-side also hold a certificate (which is not usually the case in the end-user/browser scenario). Unless, that is, TLS-PSK
TLS-PSK

Transport layer security pre-shared key ciphersuites is a set of cryptographic protocols that provide security communication based on pre-shared keys ....
 or the Secure Remote Password
Secure remote password protocol

The Secure Remote Password Protocol is a password-authenticated key agreement protocol....
 (SRP) protocol or some other protocol is used that can provide strong mutual authentication in the absence of certificates.

TLS involves three basic phases:
  1. Peer negotiation for algorithm support
  2. Key exchange and authentication
  3. Symmetric cipher encryption and message authentication


During the first phase, the client and server negotiate cipher suites, which determine the ciphers to be used, the key exchange and authentication algorithms, as well as the message authentication code
Message authentication code

A cryptography message authentication code is a short piece of information used to authenticate a message.A MAC algorithm accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC ....
s (MACs). The key exchange and authentication algorithms are typically public key algorithms, or as in TLS-PSK
TLS-PSK

Transport layer security pre-shared key ciphersuites is a set of cryptographic protocols that provide security communication based on pre-shared keys ....
 preshared keys could be used. The message authentication codes are made up from cryptographic hash functions using the HMAC
HMAC

In cryptography, a keyed-Hash Message Authentication Code , is a type of message authentication code calculated using a specific algorithm involving a cryptographic hash function in combination with a secret cryptographic key....
 construction for TLS, and a non-standard pseudorandom function
Pseudorandom function

In cryptography, a pseudorandom function family, abbreviated PRF, is a collection of efficiently-computable Function which emulate a random oracle in the following way: No efficient algorithm can distinguish between a function chosen randomly from the PRF family and a random oracle ....
 for SSL.

Typical algorithms are:
  • For key exchange: RSA
    RSA

    In cryptography, RSA is an algorithm for public-key cryptography. It is the first algorithm known to be suitable for digital signature as well as encryption, and one of the first great advances in public key cryptography....
    , Diffie-Hellman, ECDH
    Elliptic Curve Diffie-Hellman

    Elliptic Curve Diffie-Hellman is a key agreement protocol that allows two parties, each having an elliptic curve public-private key pair, to estabilish a shared secret over an insecure channel ....
    , SRP
    Secure remote password protocol

    The Secure Remote Password Protocol is a password-authenticated key agreement protocol....
    , PSK
    Pre-shared key

    In cryptography, a pre-shared key or PSK is a shared secret which was previously shared between the two parties using some secure channel before it needs to be used....
  • For authentication: RSA
    RSA

    In cryptography, RSA is an algorithm for public-key cryptography. It is the first algorithm known to be suitable for digital signature as well as encryption, and one of the first great advances in public key cryptography....
    , DSA
    Digital Signature Algorithm

    The Digital Signature Algorithm is a Federal government of the United States Federal Information Processing Standard or Federal Information Processing Standard for digital signatures....
    , ECDSA
    Elliptic Curve DSA

    Elliptic Curve DSA is a variant of the Digital Signature Algorithm which operates on elliptic curve group .As with elliptic curve cryptography in general, the bit size of the public key believed to be needed for ECDSA is about twice the size of the security level, in bits....
  • Symmetric ciphers: RC4, Triple DES
    Triple DES

    In cryptography, Triple DES is a block cipher formed from the Data Encryption Standard cipher by using it three times....
    , AES
    Advanced Encryption Standard

    In cryptography, the Advanced Encryption Standard is an encryption standard adopted by the Federal government of the United States. The standard comprises three block ciphers, AES-128, AES-192 and AES-256, adopted from a larger collection originally published as Rijndael. Each AES cipher has a 128 bit block size, with key sizes of 128...
    , IDEA
    International Data Encryption Algorithm

    In cryptography, the International Data Encryption Algorithm is a block cipher designed by Xuejia Lai and James Massey of ETH Zurich and was first described in 1991....
    , DES
    Data Encryption Standard

    The Data Encryption Standard is a block cipher that was selected by National Bureau of Standards as an official Federal Information Processing Standard for the United States in 1976 and which has subsequently enjoyed widespread use internationally....
    , or Camellia
    Camellia (cipher)

    In cryptography, Camellia is a block cipher that has been evaluated favorably by several organisations, including the European Union's NESSIE project , and the Japanese CRYPTREC project ....
    . In older versions of SSL, RC2
    RC2

    In cryptography, RC2 is a block cipher designed by Ron Rivest in 1987. "RC" stands for "Ron's Code" or "Rivest Cipher"; other ciphers designed by Rivest include RC4 , RC5 and RC6....
     was also used.
  • For cryptographic hash function
    Cryptographic hash function

    A cryptographic hash function is a algorithm that takes an arbitrary block of data and returns a fixed-size bit string, the hash value, such that an accidental or intentional change to the data will almost certainly change the hash value....
    : HMAC-MD5
    HMAC

    In cryptography, a keyed-Hash Message Authentication Code , is a type of message authentication code calculated using a specific algorithm involving a cryptographic hash function in combination with a secret cryptographic key....
     or HMAC-SHA
    HMAC

    In cryptography, a keyed-Hash Message Authentication Code , is a type of message authentication code calculated using a specific algorithm involving a cryptographic hash function in combination with a secret cryptographic key....
     are used for TLS, MD5
    MD5

    In cryptography, MD5 is a widely used cryptographic hash function with a 128-bit hash value. As an Internet standard , MD5 has been employed in a wide variety of security applications, and is also commonly used to check the integrity of computer file....
     and SHA
    Sha

    eading=Cyrillic letter Sha|Image=...
     for SSL, while older versions of SSL also used MD2 and MD4
    MD4

    MD4 is a message digest algorithm designed by Professor Ronald Rivest of Massachusetts Institute of Technology in 1990. It implements a cryptographic hash function for use in message integrity checks....
    .


History and development

Early research efforts toward transport layer security included the Secure Network Programming (SNP) API, which in 1993 explored the approach of having a secure transport layer API closely resembling sockets
Berkeley sockets

The Berkeley sockets application programming interface comprises a library for developing applications in the C that perform inter-process communication, most commonly across a computer network....
, to facilitate retrofitting preexisting network applications with security measures. The SNP project received the 2004 ACM
Association for Computing Machinery

The Association for Computing Machinery, or ACM, was founded in 1947 as the world's first scientific and educational computing society. Its membership was approximately 83,000 as of 2007....
 Software System Award.

The SSL protocol was originally developed by Netscape. Version 1.0 was never publicly released; version 2.0 was released in February 1995 but "contained a number of security flaws which ultimately led to the design of SSL version 3.0", which was released in 1996 (Rescorla 2001). This later served as the basis for TLS version 1.0, an Internet Engineering Task Force
Internet Engineering Task Force

The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the World Wide Web Consortium and International Organization for Standardization/International Electrotechnical Commission standard bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite....
 (IETF) standard protocol
Communications protocol

In the field of telecommunications, a communications protocol is the set of standard rules for data representation, Signalling , authentication and Error detection and correction required to send information over a communications channel....
 first defined in RFC 2246 in January 1999. Visa, MasterCard
MasterCard

MasterCard Worldwide is a multinational corporation based in Purchase, New York, New York, United States. Throughout the world, its principal business is to process payments between the banks of merchants and the banks of purchasers that use its "MasterCard" brand Debit card and credit cards to make purchases....
, American Express
American Express

American Express Company , sometimes known as "AmEx" or "Amex", is a Diversification global financial services company that is headquartered in New York City, New York....
 and many leading financial institutions have endorsed SSL for commerce over the Internet.

SSL operates in modular fashion. It is extensible by design, with support for forward and backward compatibility and negotiation between peers
Peer-to-peer

A peer-to-peer computer network uses diverse connectivity between participants in a network and the cumulative bandwidth of network participants rather than conventional centralized resources where a relatively low number of Server s provide the core value to a service or application....
.

Applications

TLS runs on layers beneath application protocols such as HTTP
Hypertext Transfer Protocol

Hypertext Transfer Protocol is an application-level protocol for distributed, collaborative, hypermedia information systems. Its use for retrieving inter-linked resources led to the establishment of the World Wide Web....
, FTP
File Transfer Protocol

File Transfer Protocol is a network protocol used to transfer data from one computer to another through a network such as the Internet.FTP is a file transfer protocol for exchanging and manipulating files over a Transmission Control Protocol computer network....
, SMTP
Simple Mail Transfer Protocol

Simple Mail Transfer Protocol is an Internet standard for E-mail transmission across Internet Protocol networks. SMTP was first defined in RFC 821 , and last updated by RFC 5321 , which describes the protocol in widespread use today, also known as extended SMTP ....
, NNTP
Network News Transfer Protocol

The Network News Transfer Protocol or NNTP is an Internet application Protocol used primarily for reading and posting Usenet articles , as well as transferring news among news servers....
, and XMPP
Extensible Messaging and Presence Protocol

Extensible Messaging and Presence Protocol is an open, XML-inspired network protocol originally aimed at near-real-time, extensible instant messaging and presence information , but now expanded into the broader realm of message oriented middleware....
 and above a reliable transport protocol, TCP
Transmission Control Protocol

The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is so central that the entire suite is often referred to as "TCP/IP"....
 for example. 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

Hypertext Transfer Protocol Secure is a combination of the Hypertext Transfer Protocol and a secure communication protocol.HTTP operates at the highest layer of the TCP/IP model, the Application layer; but the security protocol operates at lower sublayer, encrypting an HTTP message prior to transmission and decrypting a message upon arriva...
. HTTPS is used to secure World Wide Web
World Wide Web

The World Wide Web is a very large set of interlinked hypertext documents accessed via the Internet. With a Web browser, one can view Web pages that may contain writing, s, videos, and other multimedia and navigate between them using hyperlinks....
 pages for applications such as electronic commerce
Electronic commerce

Electronic commerce, commonly known as e-commerce or eCommerce, consists of the buying and selling of product s or Service s over electronic systems such as the Internet and other computer networks....
 and asset management
Mobile asset management

Mobile asset management is managing availability and serviceability of assets used to move, store, secure, protect and control inventory within the enterprise and along the supply chain or in conjunction with service providing....
. SMTP is also an area in which TLS has been growing and is specified in RFC 3207. These applications use public key certificate
Public key certificate

In cryptography, a public key certificate is an electronic document which incorporates a digital signature to bind together a public key with an identity — information such as the name of a person or an organization, their address, and so forth....
s to verify the identity of endpoints.

An increasing number of client and server products support TLS natively, but many still lack support. As an alternative, users may wish to use standalone TLS products like Stunnel
Stunnel

Stunnel is a free software multi-platform computer program, used to provide universal Transport Layer Security tunnelling service.Stunnel can be used to provide secure encrypted connections for clients or servers that do not speak TLS or SSL natively....
. Wrappers such as Stunnel rely on being able to obtain a TLS connection immediately, by simply connecting to a separate port
Computer port (software)

In computer programming, port has a wide range of meanings. A software port is a virtual/logical data connection that can be used by programs to exchange data directly, instead of going through a file or other temporary storage location....
 reserved for the purpose. For example, by default the TCP port for HTTPS is 443, to distinguish it from HTTP on port 80.

TLS can also be used to tunnel an entire network stack to create a VPN
Virtual private network

VPN which stands for Virtual Private Networks are used as secure extranets and Internets . It protects its network by using encryption, firewalls and other security strategies....
, as is the case with OpenVPN
OpenVPN

OpenVPN is a Free and open source software virtual private network program for creating point-to-point or server-to-multiclient encryption Tunneling protocol between host computers....
. Many vendors now marry TLS's encryption and authentication capabilities with authorization. There has also been substantial development since the late 1990s in creating client technology outside of the browser to enable support for client/server applications. When compared against traditional IPsec
IPsec

Internet Protocol Security is a Protocol suite for securing Internet Protocol communications by authentication and encryption each packet #Example: IP packets of a data stream....
 VPN technologies, TLS has some inherent advantages in firewall and NAT
Network address translation

In computer networking, network address translation is the process of modifying network address information in datagram packet headers while in transit across a traffic router for the purpose of remapping a given address space into another....
 traversal that make it easier to administer for large remote-access populations.

TLS is also increasingly being used as the standard method for protecting SIP
Session Initiation Protocol

The Session Initiation Protocol is a Signalling protocol, widely used for setting up and tearing down multimedia communication sessions such as Internet telephony and video calls over the Internet....
 application signaling. TLS can be used to provide authentication and encryption of the SIP signalling associated with VoIP and other SIP-based applications.

Security

TLS/SSL have a variety of security measures:
  • The client may use the certificate authority
    Certificate authority

    In cryptography, a certificate authority or certification authority is an entity which issues Public key certificates for use by other parties....
    's (CA's) public key to validate the CA's digital signature
    Digital signature

    A digital signature or digital signature scheme is a type of asymmetric key algorithm. For messages sent through an insecure channel, a properly implemented digital signature gives the receiver reason to believe the message was sent by the claimed sender....
     on the server certificate. If the digital signature can be verified, the client accepts the server certificate as a valid certificate issued by a trusted CA.
  • The client verifies that the issuing CA is on its list of trusted CAs.
  • The client checks the server's certificate validity period. The authentication process stops if the current date and time fall outside of the validity period.
  • Protection against a downgrade of the protocol to a previous (less secure) version or a weaker cipher suite.
  • Numbering all the Application records with a sequence number, and using this sequence number in the message authentication code
    Message authentication code

    A cryptography message authentication code is a short piece of information used to authenticate a message.A MAC algorithm accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC ....
    s (MACs).
  • Using a message digest enhanced with a key (so only a key-holder can check the MAC). This is specified in RFC 2104. TLS only.
  • The message that ends the handshake ("Finished") sends a hash of all the exchanged handshake messages seen by both parties.
  • The pseudorandom
    Pseudorandomness

    A pseudo random process is a process that appears randomness but is not. Pseudo random sequences typically exhibit statistical randomness while being generated by an entirely deterministic causal process....
     function splits the input data in half and processes each one with a different hashing algorithm (MD5
    MD5

    In cryptography, MD5 is a widely used cryptographic hash function with a 128-bit hash value. As an Internet standard , MD5 has been employed in a wide variety of security applications, and is also commonly used to check the integrity of computer file....
     and SHA-1
    SHA hash functions

    The SHA hash functions are a set of cryptographic hash functions designed by the National Security Agency and published by the National Institute of Standards and Technology as a U.S....
    ), then XORs them together to create the MAC. This provides protection even if one of these algorithms is found to be vulnerable. TLS only.
  • SSL v3 improved upon SSL v2 by adding SHA-1 based ciphers, and support for certificate authentication. Additional improvements in SSL v3 include better handshake protocol flow and increased resistance to man-in-the-middle attacks.


SSL v2 is flawed in a of ways:
  • Identical cryptographic keys are used for message authentication and encryption.
  • MACs are unnecessarily weakened in the "export mode" required by U.S. export restrictions (symmetric key length was limited to 40 bits in Netscape and Internet Explorer).
  • SSL v2 has a weak MAC construction and relies solely on the MD5 hash function.
  • SSL v2 does not have any protection for the handshake, meaning a man-in-the-middle
    Man-in-the-middle attack

    In cryptography, the man-in-the-middle attack or bucket-brigade attack , sometimes Janus attack, is a form of active eavesdropping in which the attacker makes independent connections with the victims and relays messages between them, making them believe that they are talking directly to each other over a private connection when i...
     downgrade attack can go undetected.
  • SSL v2 uses the TCP connection close to indicate the end of data. This means that truncation attacks are possible: the attacker simply forges a TCP FIN, leaving the recipient unaware of an illegitimate end of data message (SSL v3 fixes this problem by having an explicit closure alert).
  • SSL v2 assumes a single service, and a fixed domain certificate, which clashes with the standard feature of virtual hosting in webservers. This means that most websites are practically impaired from using SSL. TLS/SNI
    Server Name Indication

    Server Name Indication is a feature that fixes a flaw in the SSL v2 protocol. It permits the client to request the domain name, before the certificate is committed to by the server....
     fixes this but is not deployed in webservers as yet.


SSL v2 is disabled by default in Internet Explorer 7
Internet Explorer 7

Windows Internet Explorer 7 is a web browser released by Microsoft in October 2006. Internet Explorer 7 is part of a long line of versions of Internet Explorer and was the first major update to the browser in more than 5 years....
, Mozilla Firefox
Mozilla Firefox

Mozilla Firefox is a web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. Official versions are distributed under the terms of the proprietary EULA....
 2 and Mozilla Firefox
Mozilla Firefox

Mozilla Firefox is a web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. Official versions are distributed under the terms of the proprietary EULA....
 3, and Safari
Safari (web browser)

Safari is a web browser developed by Apple Inc.. First released as a beta on January 7, 2003 on the company's Mac OS X operating system, it became Apple's default browser beginning with Mac OS X v10.3, commonly known as "OS X Panther." Apple has also made Safari the native browser for the iPhone OS....
. After it sends a TLS ClientHello, if Mozilla Firefox finds that the server is unable to complete the handshake, it will attempt to fall back to using SSL 3.0 with an SSL 3.0 ClientHello in SSL v2 format to maximize the likelihood of successfully handshaking with older servers. Support for SSL v2 (and weak 40-bit
40-bit encryption

40-bit encryption refers to a key size of forty bits, or five bytes, for symmetric encryption; this represents a relatively low level of security....
 and 56-bit ciphers) has been removed completely from Opera
Opera (web browser)

Opera is a web browser and Internet suite developed by the Opera Software company. Opera handles common Internet-related tasks such as displaying web sites, sending and receiving e-mail messages, managing contacts, IRC online chatting, downloading files via BitTorrent , and reading web feeds....
 as of version 9.5.

How it works

A TLS client and server negotiate a stateful connection by using a handshaking procedure. During this handshake, the client and server agree on various parameters used to establish the connection's security.

  • The handshake begins when a client connects to a TLS-enabled server requesting a secure connection, and presents a list of supported ciphers
    Encryption

    In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key ....
     and hash functions
    Cryptographic hash function

    A cryptographic hash function is a algorithm that takes an arbitrary block of data and returns a fixed-size bit string, the hash value, such that an accidental or intentional change to the data will almost certainly change the hash value....
    .
  • From this list, the server picks the strongest cipher and hash function that it also supports and notifies the client of the decision.
  • The server sends back its identification in the form of a digital certificate. The certificate usually contains the server name, the trusted certificate authority
    Certificate authority

    In cryptography, a certificate authority or certification authority is an entity which issues Public key certificates for use by other parties....
     (CA), and the server's public encryption key.
The client may contact the server that issued the certificate (the trusted CA as above) and confirm that the certificate is authentic before proceeding.
  • In order to generate the session keys used for the secure connection, the client encrypts a random number (RN) with the server's public key (PbK), and sends the result to the server. Only the server can decrypt it (with its private key (PvK)): this is the one fact that makes the keys hidden from third parties, since only the server and the client have access to this data. The client knows PbK and RN, and the server knows PvK and (after decryption of the client's message) RN. A third party may only know PbK, unless PvK has been compromised.
  • From the random number, both parties generate key material for encryption and decryption.


This concludes the handshake and begins the secured connection, which is encrypted and decrypted with the key material until the connection closes.

If any one of the above steps fails, the TLS handshake fails, and the connection is not created.

TLS handshake in detail

The TLS protocol exchanges records, which encapsulate the data to be exchanged. Each record can be compressed, padded, appended with a message authentication code
Message authentication code

A cryptography message authentication code is a short piece of information used to authenticate a message.A MAC algorithm accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC ....
 (MAC), or encrypted, all depending on the state of the connection. Each record has a content type field that specifies the record, a length field, and a TLS version field.

When the connection starts, the record encapsulates another protocol - the handshake messaging protocol - which has content type 22.

Simple TLS handshake
A simple connection example , illustrating a full handshake, follows:
  • A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and compression methods.
  • The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite, and compression method from the choices offered by the client. The server may also send a session id as part of the message to perform a resumed handshake.
  • The server sends its Certificate message (depending on the selected cipher suite, this may be omitted by the server).
  • The server sends a ServerHelloDone message, indicating it is done with handshake negotiation.
  • The client responds with a ClientKeyExchange message, which may contain a PreMasterSecret, public key, or nothing. (Again, this depends on the selected cipher.)
  • The client and server then use the random numbers and PreMasterSecret to compute a common secret, called the "master secret". All other key data for this connection is derived from this master secret (and the client- and server-generated random values), which is passed through a carefully designed "pseudorandom
    Pseudorandomness

    A pseudo random process is a process that appears randomness but is not. Pseudo random sequences typically exhibit statistical randomness while being generated by an entirely deterministic causal process....
     function".
  • The client now sends a ChangeCipherSpec record, essentially telling the server, "Everything I tell you from now on will be encrypted." The ChangeCipherSpec is itself a record-level protocol, and has type 20, and not 22.
  • Finally, the client sends an encrypted Finished message, containing a hash and MAC over the previous handshake messages.
  • The server will attempt to decrypt the client's Finished message, and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be torn down.
  • Finally, the server sends a ChangeCipherSpec and its encrypted Finished message, and the client performs the same decryption and verification.
  • At this point, the "handshake" is complete and the application protocol is enabled, with content type of 23. Application messages exchanged between client and server will be encrypted.


Client-authenticated TLS handshake
The following example shows a client being authenticated via TLS using certificates.

  • A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and compression methods.
  • The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite, and compression method from the choices offered by the client. The server may also send a session id as part of the message to perform a resumed handshake.
  • The server sends its ServerCertificate message (depending on the selected cipher suite, this may be omitted by the server).
  • The server requests a certificate from the client, so that the connection can be mutually authenticated, using a CertificateRequest message.
  • The server sends a ServerHelloDone message, indicating it is done with handshake negotiation.
  • The client responds with a Certificate message, which contains the client's certificate.
  • The client sends a ClientKeyExchange message, which may contain a PreMasterSecret, public key, or nothing. (Again, this depends on the selected cipher.) This PreMasterSecret is encrypted using the public key of the server certificate.
  • The client sends a CertificateVerify message, which is a signature over the previous handshake messages using the client's certificate's private key. This signature can be verified by using the client's certificate's public key. This lets the server know that the client has access to the private key of the certificate and thus owns the certificate.
  • The client and server then use the random numbers and PreMasterSecret to compute a common secret, called the "master secret". All other key data for this connection is derived from this master secret (and the client- and server-generated random values), which is passed through a carefully designed "pseudorandom function".
  • The client now sends a ChangeCipherSpec record, essentially telling the server, "Everything I tell you from now on will be encrypted." The ChangeCipherSpec is itself a record-level protocol, and has type 20, and not 22.
  • Finally, the client sends an encrypted Finished message, containing a hash and MAC over the previous handshake messages.
  • The server will attempt to decrypt the client's Finished message, and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be torn down.
  • Finally, the server sends a ChangeCipherSpec and its encrypted Finished message, and the client performs the same decryption and verification.
  • At this point, the "handshake" is complete and the Application protocol is enabled, with content type of 23. Application messages exchanged between client and server will be encrypted.


Resumed TLS handshake
Public key operations (e.g., RSA) are relatively expensive in terms of computational power. TLS provides a secure shortcut in the handshake mechanism to avoid these operations. In an ordinary full handshake, the server sends a session id as part of the ServerHello message. The client associates this session id with the server's IP address and TCP port, so that when the client connects again to that server, it can use the session id to shortcut the handshake. In the server, the session id maps to the cryptographic parameters previously negotiated, specifically the "master secret". Both sides must have the same "master secret" or the resumed handshake will fail (this prevents an eavesdropper from using a session id). The random data in the ClientHello and ServerHello messages virtually guarantee that the generated connection keys will be different than in the previous connection. In the RFCs, this type of handshake is called an abbreviated handshake. It is also described in the literature as a restart handshake.

  • A client sends a ClientHello message specifying the highest TLS protocol version it supports, a random number, a list of suggested cipher suites and compression methods. Included in the message is the session id from the previous TLS connection.
  • The server responds with a ServerHello message, containing the chosen protocol version, a random number, cipher suite, and compression method from the choices offered by the client. If the server recognizes the session id sent by the client, it responds with the same session id. The client uses this to recognize that a resumed handshake is being performed. If the server does not recognize the session id sent by the client, it sends a different value for its session id. This tells the client that a resumed handshake will not be performed. At this point, both the client and server have the "master secret" and random data to generate the key data to be used for this connection.
  • The server now sends a ChangeCipherSpec record, essentially telling the client, "Everything I tell you from now on will be encrypted." Note that the ChangeCipherSpec is itself a record-level protocol, and has type 20, and not 22.
  • The server sends an encrypted Finished message, containing a hash and MAC over the previous handshake messages.
  • The client will attempt to decrypt the server's Finished message, and verify the hash and MAC. If the decryption or verification fails, the handshake is considered to have failed and the connection should be torn down.
  • Finally, the client sends a ChangeCipherSpec and its encrypted Finished message, and the server performs the same decryption and verification. The Finished messages are used to validate that the client and server are using the same keys. If the validation of the Finished messages fail, then the resumed handshake fails and both the client and server purge the session id information and do not use it again.
  • At this point, the "handshake" is complete and the Application protocol is enabled, with content type of 23. Application messages exchanged between client and server will be encrypted.
  • If encryption fails, the handshake will not occur.


TLS record protocol

+ Bits 0–7 8-15 16-23 24–31
0 Content Type Version (MSB) Version (LSB) Length (MSB)
32 Length (LSB) Protocol Message(s)
... Protocol Message (cont.)
... MAC
Message authentication code

A cryptography message authentication code is a short piece of information used to authenticate a message.A MAC algorithm accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC ....
 (optional)
... Padding (block ciphers only)


Content Type: This field identifies the Record Layer Protocol Type contained in this Record.

Content Types
Hex Dec Type
0x14 20 ChangeCipherSpec
0x15 21 Alert
0x16 22 Handshake
0x17 23 Application


Version: This field identifies the major and minor version of TLS for the contained message. For a ClientHello message, this need not be the highest version supported by the client.

Versions
Major Version Minor Version Version Type
3 0 SSLv3
3 1 TLS 1.0
3 2 TLS 1.1
3 3 TLS 1.2


Length: The length of Protocol message(s), not to exceed 214 bytes (16 KiB). Protocol message(s): One or more messages identified by the Protocol field. Note that this field may be encrypted depending on the state of the connection. MAC: A message authentication code computed over the Protocol message, with additional key material included. Note that this field may be encrypted, or not included entirely, depending on the state of the connection.

ChangeCipherSpec protocol

+ Bits 0–7 8-15 16-23 24–31
0 20 Version 1 (CCS protocol type) 


Alert protocol

+ Bits 0–7 8-15 16-23 24–31
0 21 Version (MSB) Version (LSB) 0
32 2 Level Description


Level: This field identifies the level of alert.

! Code ! Description>
Level Types
1 Warning - connection or security may be unstable
2 Fatal - connection or security may be compromised, or an unrecoverable error has occurred


Description: This field identifies which type of alert is being sent.

Description Types
Code Description
0 Close notify (warning or fatal)
10Unexpected message (fatal)
20Bad record MAC (fatal)
21Decryption failed (fatal, TLS only)
22Record overflow (fatal, TLS only)
30Decompression failure (fatal)
40Handshake failure (fatal)
41 No certificate (SSL v3 only) (warning or fatal)
42 Bad certificate (warning or fatal)
43 Unsupported certificate (warning or fatal)
44 Certificate revoked (warning or fatal)
45 Certificate expired (warning or fatal)
46 Certificate unknown (warning or fatal)
47Illegal parameter (fatal)
48Unknown CA (fatal, TLS only)
49Access denied (fatal, TLS only)
50Decode error (fatal, TLS only)
51 Decrypt error (TLS only) (warning or fatal)
60Export restriction (fatal, TLS only)
70Protocol version (fatal, TLS only)
71Insufficient security (fatal, TLS only)
80Internal error (fatal, TLS only)
90User cancelled (fatal, TLS only)
100 No renegotiation (warning, TLS only)


Handshake protocol

+ Bits 0–7 8-15 16-23 24–31
0 22 Version (MSB) Version (LSB) Length (MSB)
32 Length (LSB) Message type Message length
64 Message length (cont.) Handshake message
... Handshake message Message type Message length
... Message length (cont.) Handshake message


Message type: This field identifies the Handshake message type.

Message Types
Code Description
0HelloRequest
1ClientHello
2ServerHello
11Certificate
12ServerKeyExchange
13CertificateRequest
14ServerHelloDone
15CertificateVerify
16ClientKeyExchange
20Finished


Message length: This is a 3-byte field indicating the length of the handshake data, not including the header.

Note that multiple Handshake messages may be combined within one record.

Application protocol

+ Bits 0–7 8-15 16-23 24–31
0 23 Version (MSB) Version (LSB) Length (MSB)
32 Length (LSB) Application data
64 Application data (cont.)
... MAC (20B for SHA-1, 16B for MD5)
... Variable length padding (block ciphers only) Padding length, (block ciphers only)(1B)


Support for name-based virtual servers

From the application protocol point of view, TLS belongs to a lower layer, although the TCP/IP model is too coarse to show it. This means that the TLS handshake is usually (except in the STARTTLS
STARTTLS

STARTTLS is an extension to plain text communication protocols. It offers a way to upgrade a plain text connection to an encrypted connection instead of using a separate port for encrypted communication....
 case) performed before the application protocol can start. The name-based virtual server
Virtual hosting

Virtual hosting is a method that Server s such as web servers use to host more than one domain name on the same computer, sometimes on the same IP address....
 feature being provided by the application layer, all co-hosted virtual servers share the same certificate because the server has to select and send a certificate immediately after the ClientHello message. This is a big problem in hosting environments because it means either sharing the same certificate among all customers or using a different IP address for each of them.

There are two known workarounds provided by X.509
X.509

In cryptography, X.509 is an ITU-T standard for a public key infrastructure for single sign-on and Privilege Management Infrastructure . X.509 specifies, amongst other things, standard formats for public key certificates, certificate revocation lists, attribute certificates, and a certification path validation algorithm....
:
  • If all virtual servers belongs to the same domain, you can use a . Besides the loose host name selection that might be a problem or not, there is no common agreement about how to match wildcard certificates. Different rules are applied depending on the application protocol or software used.
  • Add every virtual host name in the subjectAltName extension. The major problem being that you need to reissue a certificate whenever you declare a new virtual server.


In order to provide the server name, RFC 4366 Transport Layer Security (TLS) Extensions allow clients to include a Server Name Indication
Server Name Indication

Server Name Indication is a feature that fixes a flaw in the SSL v2 protocol. It permits the client to request the domain name, before the certificate is committed to by the server....
 extension (SNI) in the extended ClientHello message. This extension hints the server immediately which name the client wishes to connect to, so the server can select the appropriate certificate to send to the client.

Government-imposed protocol limitations

Some early implementations of SSL used 40-bit
40-bit encryption

40-bit encryption refers to a key size of forty bits, or five bytes, for symmetric encryption; this represents a relatively low level of security....
 symmetric keys because of US government restrictions on the export of cryptographic technology
Export of cryptography

The export of cryptography is the transfer from one country to another of devices and technology related to cryptography.Since World War II, many governments, including the United States and its NATO allies, have regulated the export of cryptography for national security considerations, and, for a time, defined cryptography to be a munition...
. After several years of public controversy, a series of lawsuits, and eventual US government recognition of cryptographic products with longer key sizes produced outside the US, the authorities relaxed some aspects of the export restrictions.

Implementations

SSL and TLS have been widely implemented in several open source
Open source

Open source is an approach to design, development, and distribution offering practical accessibility to a product's source . Some consider open source as one of various possible design approaches, while others consider it a critical Strategy element of their business operations....
 software projects. Programmers may use the OpenSSL
OpenSSL

OpenSSL is an open source implementation of the Transport Layer Security protocols. The core library implements the basic cryptography functions and provides various utility functions....
, NSS
Network Security Services

In computing, Network Security Services comprises a set of Library designed to support cross-platform development of security-enabled client and server applications....
, or GnuTLS
GnuTLS

GnuTLS , the GNU Transport Layer Security Library, is a free software implementation of the Transport Layer Security protocols. Its purpose is to offer an application programming interface for applications to enable secure communication protocols over their network transport layer....
 libraries for SSL/TLS functionality. Microsoft Windows
Microsoft Windows

Microsoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces ....
 includes an implementation of SSL and TLS as part of its Secure Channel
Security Support Provider Interface

SSPI is an Application programming interface used by Microsoft Windows systems to perform a variety of security related operations such as authentication....
 package. Delphi programmers may use a library called Indy.

Browser implementation

As of Presto
Presto (layout engine)

Presto is a layout engine for the Opera developed by Opera Software. After several public betas and technical previews, it was released on January 28, 2003 in Opera 7.0 for Windows; it is the browser's current layout engine....
 2.2, featured in Opera
Opera (web browser)

Opera is a web browser and Internet suite developed by the Opera Software company. Opera handles common Internet-related tasks such as displaying web sites, sending and receiving e-mail messages, managing contacts, IRC online chatting, downloading files via BitTorrent , and reading web feeds....
 10, Opera supports TLS 1.2 .

Standards

The current approved version is 1.2, which is specified in:
  • RFC 5246: “The Transport Layer Security (TLS) Protocol Version 1.2”.


The current standard obsoletes these former versions:
  • RFC 2246: “The TLS Protocol Version 1.0”.
  • RFC 4346: “The Transport Layer Security (TLS) Protocol Version 1.1”.


Other RFC
Request for Comments

In computer network engineering, a request for comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems....
s subsequently extended TLS, including:
  • RFC 2595: “Using TLS with IMAP, POP3 and ACAP”. Specifies an extension to the IMAP, POP3 and ACAP services that allow the server and client to use transport-layer security to provide private, authenticated communication over the Internet.
  • RFC 2712: “Addition of Kerberos Cipher Suites to Transport Layer Security (TLS)”. The 40-bit ciphersuites defined in this memo appear only for the purpose of documenting the fact that those ciphersuite codes have already been assigned.
  • RFC 2817: “Upgrading to TLS Within HTTP/1.1”, explains how to use the Upgrade mechanism in HTTP/1.1 to initiate Transport Layer Security (TLS) over an existing TCP connection. This allows unsecured and secured HTTP traffic to share the same well known port (in this case, http: at 80 rather than https: at 443).
  • RFC 2818: “HTTP Over TLS”, distinguishes secured traffic from insecure traffic by the use of a different 'server port'.
  • RFC 3207: “SMTP Service Extension for Secure SMTP over Transport Layer Security”. Specifies an extension to the SMTP service that allows an SMTP server and client to use transport-layer security to provide private, authenticated communication over the Internet.
  • RFC 3268: “AES Ciphersuites for TLS”. Adds Advanced Encryption Standard
    Advanced Encryption Standard

    In cryptography, the Advanced Encryption Standard is an encryption standard adopted by the Federal government of the United States. The standard comprises three block ciphers, AES-128, AES-192 and AES-256, adopted from a larger collection originally published as Rijndael. Each AES cipher has a 128 bit block size, with key sizes of 128...
     (AES) ciphersuites to the previously existing symmetric ciphers.
  • RFC 3546: “Transport Layer Security (TLS) Extensions”, adds a mechanism for negotiating protocol extensions during session initialisation and defines some extensions. Made obsolete by RFC 4366.
  • RFC 3749: “Transport Layer Security Protocol Compression Methods”, specifies the framework for compression methods and the DEFLATE
    DEFLATE

    Deflate is a lossless data compression algorithm that uses a combination of the LZ77 and LZ78 algorithm and Huffman coding. It was originally defined by Phil Katz for version 2 of his PKZIP archiving tool, and was later specified in RFC 1951....
     compression method.
  • RFC 3943: “Transport Layer Security (TLS) Protocol Compression Using Lempel-Ziv-Stac (LZS)”.
  • RFC 4132: “Addition of Camellia
    Camellia (cipher)

    In cryptography, Camellia is a block cipher that has been evaluated favorably by several organisations, including the European Union's NESSIE project , and the Japanese CRYPTREC project ....
     Cipher Suites to Transport Layer Security (TLS)”.
  • RFC 4162: “Addition of SEED
    Seed

    A seed is a small Plant embryogenesis plant enclosed in a covering called the seed coat, usually with some Food storage. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant....
     Cipher Suites to Transport Layer Security (TLS)”.
  • RFC 4217: “Securing FTP with TLS
    FTPS

    FTPS is an extension to the commonly used File Transfer Protocol that adds support for the Transport Layer Security and the Secure Sockets Layer cryptographic protocols....
    ”.
  • RFC 4279: “Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)”, adds three sets of new ciphersuites for the TLS protocol to support authentication based on pre-shared keys.
  • RFC 4347: “Datagram Transport Layer Security
    Datagram Transport Layer Security

    In information technology, the Datagram Transport Layer Security protocol provides communications privacy for packet protocols. DTLS allows datagram-based applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery....
    ” specifies a TLS variant that works over datagram protocols (such as UDP).
  • RFC 4366: “Transport Layer Security (TLS) Extensions” describes both a set of specific extensions, and a generic extension mechanism.
  • RFC 4492: “Elliptic Curve Cryptography
    Elliptic curve cryptography

    Elliptic curve cryptography is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. The use of elliptic curves in cryptography was suggested independently by Neal Koblitz and Victor S....
     (ECC) Cipher Suites for Transport Layer Security (TLS)”.
  • RFC 4507: “Transport Layer Security (TLS) Session Resumption without Server-Side State”.
  • RFC 4680: “TLS Handshake Message for Supplemental Data”.
  • RFC 4681: “TLS User Mapping Extension”.
  • RFC 4785: “Pre-Shared Key (PSK) Ciphersuites with NULL Encryption for Transport Layer Security (TLS)”.


See also


  • Certificate authority
    Certificate authority

    In cryptography, a certificate authority or certification authority is an entity which issues Public key certificates for use by other parties....
  • Public key certificate
    Public key certificate

    In cryptography, a public key certificate is an electronic document which incorporates a digital signature to bind together a public key with an identity — information such as the name of a person or an organization, their address, and so forth....
  • Extended Validation Certificate
  • SSL acceleration
    SSL acceleration

    SSL acceleration is a method of offloading the processor-intensive public key encryption algorithms involved in Transport Layer Security transactions to a hardware accelerator....
  • Datagram Transport Layer Security
    Datagram Transport Layer Security

    In information technology, the Datagram Transport Layer Security protocol provides communications privacy for packet protocols. DTLS allows datagram-based applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery....
  • Multiplexed Transport Layer Security
    Multiplexed Transport Layer Security

    In information technology, the Transport Layer Security protocol provides connection security with mutual authentication, data confidentiality and integrity, key generation and distribution, and security parameters negotiation....
  • X.509
    X.509

    In cryptography, X.509 is an ITU-T standard for a public key infrastructure for single sign-on and Privilege Management Infrastructure . X.509 specifies, amongst other things, standard formats for public key certificates, certificate revocation lists, attribute certificates, and a certification path validation algorithm....
  • Virtual private network
    Virtual private network

    VPN which stands for Virtual Private Networks are used as secure extranets and Internets . It protects its network by using encryption, firewalls and other security strategies....
  • SEED
    Seed

    A seed is a small Plant embryogenesis plant enclosed in a covering called the seed coat, usually with some Food storage. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant....
  • Server gated cryptography
    Server gated cryptography

    Server Gated Cryptography was created in response to United States federal legislation on the export of cryptography in the 1990s.The legislation had limited encryption to weak algorithms and shorter key lengths if used in software outside of the United States....


Software

  • OpenSSL
    OpenSSL

    OpenSSL is an open source implementation of the Transport Layer Security protocols. The core library implements the basic cryptography functions and provides various utility functions....
    : a free implementation (BSD license with some extensions)
  • GnuTLS
    GnuTLS

    GnuTLS , the GNU Transport Layer Security Library, is a free software implementation of the Transport Layer Security protocols. Its purpose is to offer an application programming interface for applications to enable secure communication protocols over their network transport layer....
    : a free implementation (LGPL licensed)
  • JSSE: a Java
    Java (programming language)

    Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java ....
     implementation included in the Java Runtime Environment
  • Network Security Services
    Network Security Services

    In computing, Network Security Services comprises a set of Library designed to support cross-platform development of security-enabled client and server applications....
     (NSS): FIPS 140
    FIPS 140

    The Federal Information Processing Standard 140 are series of publications numbered 140 which are a United States government of the United States computer security standardization that specify requirements for cryptographic modules....
     validated open source library


Further reading




External links

  • (published 1994)
  • (published 1996)