A cryptographic protocol is an abstract or concrete protocol that performs a security-related function and applies cryptographic methods. The most widely used cryptographic protocols are protocols for secure application-level data transport. A cryptographic protocol of this kind usually incorporates at least some of these aspects:
Symmetric encryption and message authentication material construction
Secured application-level data transport
Non-repudiation methods
For example, Transport Layer Security (TLS) is a cryptographic protocol that is used to secure web (HTTP) connections. It has an entity authentication mechanism, based on the X.509 system; a key setup phase, where a symmetric encryption key is formed by employing public-key cryptography; and an application-level data transport function. These three aspects have important interconnections. Standard TLS does not have non-repudiation support.
There are other types of cryptographic protocols as well, and even the term itself has various different readings. For instance, TLS employs what is known as the Diffie-Hellman key exchange, an although only a part of TLS per se, it can be also seen as a complete cryptographic protocol of its own right.
Cryptographic protocols can sometimes be verified formally on an abstract level.
A security protocol (or cryptographicprotocol) is an abstract or concrete protocol that performs a security-related function and applies cryptographic methods.
Cryptographicprotocols are widely used for secure application-level data transport.
There are other types of cryptographicprotocols as well, and even the term itself has various different readings; Cryptographic application protocols often use one or more underlying key agreement methods, which are also sometimes themselves referred to as "cryptographicprotocols".
After the discovery of flaws in a protocol, the flaws are often corrected or approaches are being adopted to avoid using the reasoning of the flawed protocols [4].
In the case of protocolauthentication, FDR is used to test whether the protocol correctly achieves authentication and discover a specific kind of attack of the protocol: this is the case where an intruder is masquerading as another one within a protocol run.
The NRL Protocol Analyzer has been used successfully to locate a series of previously unknown flaws in a number of protocols [45] [46], and to demonstrate flaws that were already known in the literature [47].