Transport To bush-hammer Security

Transport To bush-hammer Security ( TLS ), in the past named Secure Socket To bush-hammer ( SSL ), is a protocol of security of the exchanges on Internet, developed originally by Netscape (SSL version 2 and SSL version 3). It was famous in Transport To bush-hammer Security (TLS) by IETF following the repurchase of the patent of Netscape by the IETF in 2001. The work group corresponding to the IETF allowed the creation of the RFC 2246 for the TLS and RFC 4347 for its equivalent in mode datagram, DTLS.

There is very little difference between SSL version 3 and TLS version 1 (which corresponds to version 3.1 of protocol SSL) making the two protocols noninter-operable, but TLS installed a mechanism of upward compatibility with SSL. Moreover, TLS differs from SSL for the generation of the symmetrical key . This generation is protected in TLS than in SSL v3 insofar as no stage of the algorithm rests solely on MD5 for which some weaknesses in Cryptanalyse appeared.

By abuse language, one speaks about SSL to indicate SSL or TLS indifferently.

SSL functions according to a mode Client-serveur. It provides four objectives of safety:

Presentation

With the development of Internet, many business firms propose online shoppings for the private individuals. The offer grows the every day, but the turnover released by the e-business (E-trade) remains still modest because the customer does not have yet a total confidence in the credit card payment. One in the ways of making safe this payment is to use protocols of authentification and coding such as SSL , but that does not exempt the tradesman to carefully take care of the card numbers banking sometimes stored on its waiters.

The quantified session is generally used at the time of the sending of the banking card number, but it can the being in other cases. Coding is carried out by at the same time an asymmetrical coding (which will allow an authentification) such as for example the algorithm RSA and at the same time by a symmetrical coding (which is lighter than an asymmetrical coding) and which will ensure the transmission of information (such as for example the OF the). One there assistant a Function of chopping as MD5 to make sure that the data are transmitted without being corrupted. SSL is used by the majority of the navigators. It is recognized that a transaction is protected when a key or a closed cadena is posted in a lower corner of the screen as in the bar of address, the address starts with https://..

Operation

In the pile of protocol TCP/IP, SSL is located between the applications layers (like HTTP, ftp, smtp, etc ) and lay down it transport TCP.
Son the most common use remains however in top of HTTP. Layer SSL is implemented by the application layer of the pile, which has two conséquences :
  • for all existing applications, it can exist an application using SSL. For example, application HTTPS corresponds to HTTP to the top of SSL  ;
  • an application SSL is seen allotting a new number of port by IANA. For example HTTPS is associated with port 443.

Navigators Web

The majority of the navigators Web manage perfectly SSLv2, SSLv3 & TLS v1.0 (this last not being activated by defect under Internet Explorer 6). However, it would seem that SSLv2 is decontaminated by defect in the next grinding of Internet Explorer (version 7), which would oblige with the majority of the salesmen on line to modify the configuration of their waiters (altogether tiny modifications), like points out it this article of ZDNet.fr. It would also seem that to date (March 2006), only the navigator Opera version 9 is able to fully manage version 1.1 of TLS.

Authentification of customer SSL by numerical certificate

In the majority of the cases, the user authenticates the waiter SSL on which it is connected. This authentification is carried out by the use of a numerical certificate X509 delivered by an authority of confidence (AC). But more and more of Web applications use now the authentification of the station customer by exploiting SSL. It is then possible to offer a mutual authentification between the customer and the waiter. The certificate customer can be stored in format software on the station customer or with the format hardware (Smart card, Token USB) to increase the safety of bond SSL. This solution makes it possible to offer mechanisms of strong Authentification

The diagram below gives an outline of the operation of the authentification customer SSL.

Attacks

In 2001, Serge Vaudenay discovers a Attaque by auxiliary channel against SSL. This attack benefits from a bad implementation of the filling which is used when the entries have a variable size. The Mode of coding CBC (cipher block chaining) consists in dividing the data into several of the same blocks cuts and quantifying them in a chained way (the preceding result is used during following coding). The attack of Vaudenay uses the response times of the waiters in the event of errors during the filling. With a little chance, it is possible to discover the last data which were sent and to recover them. The attack is however inoperative with a coding of the type RC4 and is valid only under certain conditions. It in spite of was very used successfully against certain “webmails” which send several times the same data. Following this attack, the standard was updated.

Texts of reference

The first formal text defining protocol TLS is the RFC 2246 published by the IETF in 1999.

Other texts followed on this protocole :

  • RFC 2712: Addition of the continuation Kerberos in TLS  ;
  • RFC 2817: Passage to TLS at a session HTTP 1.1  ;
  • RFC 2818: HTTP on TLS  ;
  • RFC 3268: Use of the system of coding AES for TLS.

See too

Related articles

External bonds

  • Introduction to SSL

  • Web site of OpenSSL
  • Technology VPN SSL vs IPSEC
  • a very good article on the authentification Customer SSL. Example with a server Apache

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