Posts Tagged ‘TLS

SSL/TLS Cipher Suites

A cipher suite combines four kinds of security features, and is given a name in the SSL protocol specification. Before data flows over a SSL connection, both ends attempt to negotiate a cipher suite. This lets them establish an appropriate quality of protection for their communications, within the constraints of the particular mechanism combinations which are available. The features associated with a cipher suite are:

A given implementation of SSL will support a particular set of cipher suites, and some subset of those will be enabled by default. Applications have a limited degree of control over the cipher suites that are used on their connections; they can enable or disable any of the supported cipher suites, but cannot change the cipher suites that are available.

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Transport Layer Security Protocol

TLS (Transport Layer Security) was released in response to the Internet community’s demands for a standardized protocol. The IETF provided a venue for the new protocol to be openly discussed, and encouraged developers to provide their input to the protocol.

The TLS protocol was released in January 1999 to create a standard for private communications. The protocol “allows client/server applications to communicate in a way that is designed to prevent eavesdropping,tampering or message forgery.” According to the protocol’s creators, the goals of the TLS protocol are cryptographic security, interoperability, extensibility, and relative efficiency.These goals are achieved through implementation of the TLS protocol on two levels: the TLS Record protocol and the TLS Handshake protocol.

TLS Record Protocol

The TLS Record protocol negotiates a private, reliable connection between the client and the server. Though the Record protocol can be used without encryption, it uses symmetric cryptography keys, to ensure a private connection. This connection is secured through the use of hash functions generated by using a Message Authentication Code.

TLS Handshake Protocol

The TLS Handshake protocol allows authenticated communication to commence between the server and client. This protocol allows the client and server to speak the same language, allowing them to agree upon an encryption algorithm and encryption keys before the selected application protocol begins to send data. Using the same handshake protocol procedure as SSL, TLS provides for authentication of the server, and optionally, the client.

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Use of SOAP over HTTP

Since the SOAP binding requires that conformant applications support HTTP over TLS/SSL with a number of different bilateral authentication methods such as Basic over server-side SSL and certificate-backed authentication over server-side SSL, these methods are always available to mitigate threats in cases where other lower-level systems are not available and the above listed attacks are considered significant threats.

This does not mean that use of HTTP over TLS with some form of bilateral authentication is mandatory. If an acceptable level of protection from the various risks can be arrived at through other means (for example, by an IPsec tunnel), full TLS with certificates is not required. However, in the majority of cases for SOAP over HTTP, using HTTP over TLS with bilateral authentication will be the appropriate choice.

The HTTP Authentication RFC describes possible attacks in the HTTP environment when basic or message-digest authentication schemes are used. Note, however, that the use of transport-level security (such as the SSL or TLS protocols under HTTP)only provides confidentiality and/or integrity and/or authentication for “one hop”. For models where there may be intermediaries, or the assertions in question need to live over more than one hop, the use of  HTTP with TLS/SSL does not provide adequate security.

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