What is transport Layer Security?
Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL) are cryptographic protocols that allow secure communication and data integrity over TCP / IP, for example, the Internet. TLS and SSL encrypt the communication from source to destination (end-to-end) on the transport layer.
Different versions of the protocol are widely used in applications such as browsing, e-mail, instant messaging and Voice over IP.
TLS is an IETF standard protocol that, in its latest version, is defined in RFC 5246, developed on the basis of the previous SSL protocol from Netscape Corporation.
The TLS protocol allows client / server applications to communicate over a network so as to prevent the ‘tampering’ (tampering) of data, tampering and interception.
Typical use of a browser by the end user, authentication, TLS is unilateral: only the server is authenticated (the client knows the identity of the server), but not vice-versa (the client remains anonymous and authenticated) . The authentication server is very useful for navigation software and the user.
The browser validates the server certificate by checking the digital signature server certificate check that this is valid and recognized by a known certificate authority using public key cryptography. After this authentication, the browser indicates a secure connection usually show a padlock icon in the lower right.
This authentication, however, is not sufficient to ensure that the site with which you connected is the one required. To be sure it is necessary to analyze the contents of the certificate and checking the certification chain. Sites that want to trick you can not use a certificate of the site that wants to act because they have the ability to encrypt a valid certificate, which includes the address, so that it is valid to the destination.
Only the CA can generate valid certificates embedded with a URL so that the comparison between apparent and that the URL contained in the certificate can certainly provide a method for identification of the site. Very often this mechanism is not known to internet users and is the cause of various frauds due, however, to an incorrect use of the browser not to a weakness of the TLS protocol.
The TLS protocol also allows bilateral authentication, typically used in business applications, in which both parties are authenticated securely exchanging certificates. This authentication (defined Mutual authentication) requires that the client has its own digital certificate which is very unlikely in a normal scenario.
In the absence of bilateral authentication you can use the TLS-PSK or Secure Remote Password (SSP) to ensure secure authentication without a certificate.
TLS Protocol Phases
The operation of the TLS protocol can be divided into three main phases:
- Negotiation between the parties of the algorithm used
- Key Exchange and Authentication
- Symmetric encryption and message authentication
In the first phase, the client and server negotiate the encryption protocol to be used for the secure communication protocol for key exchange and authentication algorithm and the Message Authentication Code (MAC). The algorithm for key exchange and one for authentication, public key algorithms are normally or, as in the case of TLS-PSK, using a pre-shared key (Pre-Shared Key). Message authentication is guaranteed by a hash algorithm that uses an HMAC construct for TLS pseudo-random function or a non-standard SSL.
Protocols used Within A Session
‘Within a session’ typically uses the following protocols:
- For key exchange: RSA, ECDH, SRP, PSK
- For authentication: RSA, DSA, ecdsa
- Symmetric Encryption: RC4, Triple DES, AES, IDEA, DES, or Camellia. In older versions of SSL protocol was also used RC2.
- For cryptographic hash functions: TLS are used in HMAC-MD5 or HMAC-SHA and MD5 and SHA in SSL. In older versions of SSL were also used MD2 and MD4.
Early implementations of SSL were limited to symmetric key encryption to 40 bits because of the restrictions imposed by the U.S. government on the export of cryptographic technology. The limitation of 40-bit key size was explicitly set to make the cipher weak enough that they can be forced (through the use of brute force search techniques) by the judicial authorities who wish to decipher the encrypted traffic, but strong enough to attack by entities with fewer financial resources.
After several years of public controversy, its causes and the admission by the U.S. government to market availability of encryption products for ‘better’ (both within and outside the United States), some aspects of restrictions have been finally modified. Modern implementations using symmetric encryption keys to a 128 (or more) bits.
Although currently a growing number of client and server products support TLS or SSL natively, there are still many products that do not support these protocols. In these cases it is possible to use products that provide SSL encryption on its own.
Study: From Wikipedia, the free encyclopedia. The text is available under the Creative Commons.
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Tags: Transport Layer Security