Cipher suite – Wikipedia

Set of algorithm that help secure a network association
A cipher suite is a set of algorithm that help secure a network association. Suites typically use Transport Layer Security ( TLS ) or its now-deprecated harbinger Secure Socket Layer ( SSL ). The set of algorithm that code suites normally contain include : a key exchange algorithm, a bulge encoding algorithm, and a message authentication code ( MAC ) algorithm. [ 1 ] The key exchange algorithm is used to exchange a key between two devices. This key is used to encrypt and decrypt the messages being sent between two machines. The bulk encoding algorithm is used to encrypt the data being sent. The MAC algorithm provides data integrity checks to ensure that the data sent does not change in transit. In addition, zero suites can include signatures and an authentication algorithm to help authenticate the waiter and or node. overall, there are hundreds of different cipher suites that contain different combinations of these algorithms. Some cipher suites offer better security than others.

The structure and function of the zero cortege concept are defined in the TLS standard document. [ 2 ] TLS 1.2 is the most prevailing interpretation of TLS. The future version of TLS ( TLS 1.3 ) includes extra requirements to cipher suites. TLS 1.3 was only recently standardised and is not yet widely used. Cipher suites defined for TLS 1.2 can not be used in TLS 1.3, and vice versa, unless differently stated in their definition. A address list of named cipher suites is provided in the TLS Cipher Suite Registry. [ 3 ]

history [edit ]

The practice of ciphers has been a partially of the Secure Socket Layer ( SSL ) theodolite protocol since its creation. SSL has been succeeded by TLS for most uses. however, the identify Cipher Suite was not used in the original draft of SSL. rather the ability for a customer and a server to choose from a belittled set of ciphers to secure their connection was called Cipher-Choice. [ 4 ] [ 5 ] It was not until SSL v3 ( the last translation of SSL ) that the name Cipher Suite was used. [ 6 ] Every version of TLS since has used Cipher Suite in its calibration. The concept and aim of a Cipher Suite has not changed since the term was first coined. It has and still is used as a structure describing the algorithm that a machine supports in decree for two machines to decide which algorithm to use to secure their connection. What has changed is the versions of the algorithm that are supported in the cipher suites. Each interpretation of TLS has added support for stronger versions of the algorithm and removed support for versions of the algorithm that have been identified as insecure. TLS 1.3 marks a variety in how cipher suites are coordinated between machines. The cipher suite chosen for two communicating machines to use is determined by the handshake process. Modifications were done in TLS 1.3 to the handshake process to cut down on the numeral of messages needed to be sent. This allows for less serve, less packet traffic and more efficiency compared to previous versions of TLS .

Naming schema [edit ]

Each cipher suite has a singular diagnose that is used to identify it and to describe the algorithmic contents of it. Each segment in a cipher suite diagnose stands for a unlike algorithm or protocol. An model of a nothing suite name : TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 The meaning of this name is :

  • TLS defines the protocol that this cipher suite is for; it will usually be TLS.
  • ECDHE indicates the key exchange algorithm being used.
  • RSA authentication mechanism during the handshake.
  • AES session cipher.
  • 128 session encryption key size (bits) for cipher.
  • GCM type of encryption (cipher-block dependency and additional options).
  • SHA (SHA2)hash function. For a digest of 256 and higher. Signature mechanism. Indicates the message authentication algorithm which is used to authenticate a message.
  • 256 Digest size (bits).

Full handshake : coordinate nothing suites [edit ]

To use zero suites, the node and the waiter must agree on the specific cipher cortege that is going to be used in exchanging messages. Both the client and the server must support the agreed upon cipher cortege. If the customer and server do not agree on a cipher cortege, no connection will be made. [ 7 ] This excerpt process occurs during the TLS Handshake Protocol. TLS 1.3 includes a TLS Handshake Protocol that differs compared to past and the current interpretation of TLS/SSL. After coordinating which cipher suite to use, the server and the node still have the ability to change the organize ciphers by using the ChangeCipherSpec protocol in the current handshake or in a new handshake. To test which TLS ciphers a waiter supports, an SSL/TLS Scanner may be used. [ 1 ]

TLS 1.0–1.2 handshake [edit ]

ocular representation of how a customer and server engage on TLS 1.2 organize which cipher suite to use This customer starts the serve by sending a clientHello message to the server that includes the interpretation of TLS being used and a list of cipher suites in the ordain of the node ‘s preference. In response, the waiter sends a serverHello message that includes the choose calculate suite and the seance ID. Next the server sends a digital security to verify its identity to the customer. The server may besides request a node ‘s digital certificate if needed. If the client and server are not using pre-shared keys, the node then sends an code message to the server that enables the node and the waiter to compute which secret key will be used during exchanges. After successfully verifying the authentication of the server and, if needed, exchanging the unavowed key, the customer sends a finished message to signal that it is done with the handshake work. After receiving this message, the waiter sends a finished message that confirms that the handshake is arrant. nowadays the client and the server are in agreement on which cipher suite to use to communicate with each other .
ocular representation of how a client and server operating on TLS 1.3 coordinate which cipher suite to use

TLS 1.3 handshake [edit ]

If two machines are corresponding over TLS 1.3, they coordinate which cipher suite to use by using the TLS 1.3 Handshake Protocol. The handshake in TLS 1.3 was condensed to only one attack tripper compared to the two round off trips required in previous versions of TLS/SSL. first gear the customer sends a clientHello message to the server that contains a number of support ciphers in order of the client ‘s predilection and makes a guess on what keystone algorithm is being used so that it can send a hidden key to share if needed. By making a think on what key algorithm that is being used it eliminates a rung slip. After receiving the clientHello, the waiter sends a serverHello with its key, a certificate, the choose cipher suite and the finished message. After the node receives the server ‘s finished message it now is coordinated with the server on which cipher suite to use. [ 8 ]

Supported algorithm [edit ]

In TLS 1.0–1.2 [edit ]

For more information about algorithm supported in TLS 1.0–1.2, attend besides : Transport Layer Security § Applications and adoption

TLS 1.3 [edit ]

In TLS 1.3, many bequest algorithms that were supported in early versions of TLS have been dropped in an feat to make the protocol more secure. [ 9 ] In addition, all encoding and authentication algorithms are combined in the authenticate encoding with associated data ( AEAD ) encoding algorithm. besides a hash algorithm must now be used in HMAC-based key derivation ( HKDF ). [ 10 ] All non-AEAD ciphers have been removed due to possible weaknesses or vulnerabilities and ciphers must use an ephemeral winder exchange algorithm so that new key pairs are generated for every exchange. [ 11 ]

DTLS with calculate suites [edit ]

Datagram Transport Layer Security ( DTLS ) is based on TLS, but is specifically used for UDP connections rather of TCP connections. Since DTLS is based on TLS it is able to use a majority of the cipher suites described for TLS. There are especial cases that must be considered when using TLS cipher suites with DTLS. DTLS does not support the stream nothing RC4 which means that no TLS code using RC4 can be used with DTLS. [ 12 ] To determine if a TLS nothing cortege is compatible with DTLS looking at its mention will not help. Each TLS cipher cortege will hush include the TLS identifier space in its diagnose. e.g. : TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256. alternatively, all TLS parameter registries now include the sag DTLS-OK to signal if a zero suite supports DTLS. [ 13 ]

Vulnerabilities [edit ]

A cipher cortege is equally batten as the algorithm that it contains. If the translation of encoding or authentication algorithm in a cipher suite have known vulnerabilities the calculate cortege and TLS connection may then vulnerable. Therefore, a common attack against TLS and cipher suites is known as a downgrade attack. A downgrade in TLS occurs when a modern client connects to bequest servers that are using older versions of TLS or SSL. When initiating a handshake, the modern node will offer the highest protocol that it supports. If the connection fails, it will automatically retry again with a lower protocol such as TLS 1.0 or SSL 3.0 until the handshake is successful with the waiter. The aim of downgrade is so that new versions of TLS are compatible with older versions. however, it is possible for an adversary to take advantage of this feature and make it therefore that a customer will automatically downgrade to a version of TLS or SSL that supports cipher suites with algorithm that are known for unaccented security and vulnerabilities. [ 14 ] This has resulted in attacks such as POODLE. One way to avoid this security defect is to disable the ability of a server or customer to be able to downgrade to SSL 3.0. The shortcoming with this sterilize is that it will make it so that some bequest hardware can not be accessed by newer hardware. If SSL 3.0 digest is needed for bequest hardware, there is an approved TLS_FALLBACK_SCSV nothing suite which verifies that downgrades are not triggered for malicious intentions. [ 15 ]

Cipher suites for restrain devices [edit ]

encoding, key exchange and authentication algorithms normally require a big amount of processing baron and memory. To provide security to constrained devices with limited processing world power, memory, and battery life sentence such as those powering the Internet of things there are specifically chosen cipher suites. Two examples include :
Each of these cipher suites has been implemented to run on devices with constraints in processing office and memory. They are both implemented in the open-sourced project TinyDTLS. The rationality that they are able to work on these constrained devices is because they can be implemented in a light-weight manner. Implementations of the pre-shared key cipher suite used only 1889 bytes of RAM and 38266 of brassy ROM which is very resource-conscious compared to most encoding and security algorithm. [ 17 ] This moo memory use is due to these cipher suites using test efficient algorithm that are dependable, but possibly not a secure as more resource-required algorithm ; exp : Using 128 bit encoding vs 256 bit encoding. In addition they use pre-shared key or raw public key which requires less memory space and processing power compared to using traditional public key infrastructure ( PKIX ). [ 18 ]

Programming references [edit ]

In programming, a cipher suite is referred to in both plural and non-plural forms. Each one has different definitions :

CipherSuite cipher_suites
a list of the cryptographic options supported by the client.[19] An example of how cipher_suites is usually used during the handshake process:
 struct  {
 ProtocolVersion  client_version ;
 random  random ;
 SessionID  session_id ;
 CipherSuite  cipher_suites < 2..2 ^ 16-2 > ;
 CompressionMethod  compression_methods < 1..2 ^ 8-1 > ;
 blue-ribbon  ( extensions_present )  {
 case  false :
 struct  { } ;
 lawsuit  true : 
 extension  extensions < 0..2 ^ 16-1 > ;
 } ;
 }  ClientHello ;
CipherSuite cipher_suite
the cipher suite selected by the server from the client’s cipher_suites.[20] An example of how cipher_suite is usually used during the handshake process:
 struct  {
 ProtocolVersion  server_version ;
 random  random ;
 SessionID  session_id ;
 CipherSuite  cipher_suite ;
 CompressionMethod  compression_method ;
 choice  ( extensions_present )  {
 encase  false :
 struct  { } ;
 sheath  true :
 extension  extensions < 0..2 ^ 16-1 > ;
 } ;
 }  ServerHello ;

See besides [edit ]

References [edit ]

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