Cryptography works on many levels. On one level you have algorithms, such as symmetric block ciphers and public-key algorithms. Building upon these you obtain protocols, and building upon protocols you find applications (or other protocols).
It is not sufficient to study the security of the underlying algorithms alone, as a weakness on a higher-level protocol (or application) can render the application insecure regardless of how good the underlying cryptographic algorithms are. A simple example is a protocol that leaks information about the key being used to encrypt the communication channel. Irrespective of how good the encryption algorithms are, they are rendered insecure if the overlying protocol reveals information on the keys used in encryption.
The analysis of protocols is often difficult because the applications that implement such protocols may lead to further problems. Thus a good protocol is not enough, you must also have a good and robust implementation.
In the following, several well-known protocols and standards are mentioned.
- Domain Name Server Security (DNSSEC).
This is a protocol for secure distributed name services. It is defined in RFC 3007 and RFC 3008. - Generic Security Services API (GSSAPI)
GSSAPI provides an authentication, key exchange, and encryption interface to different cryptographic algorithms and systems. It is defined in RFC 2743. - Secure Socket Layer (SSL) / Transport Layer Security (TLS)
SSL is one of the two protocols for secure WWW connections (the other is SHTTP). WWW security has become important as increasing amounts of sensitive information, such as credit card numbers, are being transmitted over the Internet.
SSL was originally developed by Netscape in 1994 as an open protocol standard. The internet draft of the SSL Protocol 3.0 can be found here. In 1996, SSL development became the responsibility of the Internet Engineering Task Force (IETF) and it renamed SSL to TLS (Transport Layer Security). However, TLS 1.0 differs very little from SSL 3.0. Extensions for TLS are described in RFC 3546. - Secure Hypertext Transfer Protocol (SHTTP)
This is another protocol for providing more security for WWW transactions. In many ways it is more flexible than SSL, but due to Netscape's original dominance in the marketplace SSL/TLS is in a very strong position. SHTTP is defined in RFC 2660. - E-Mail security and related services
- OpenPGP is a standardization of what Phil Zimmermann's PGP already did for many years. But now that it is a standard, different implementations come into existence.
- Secure-MIME (S/MIME) is an alternative for the OpenPGP standard maintained by the IETF working group S/MIME.
- OpenPGP is a standardization of what Phil Zimmermann's PGP already did for many years. But now that it is a standard, different implementations come into existence.
- Public Key Encryption Standards (PKCS)
These standards are developed at RSA Data Security and define safe ways to use RSA. The PKCS documents published by RSA Laboratories are available at their web site. - IEEE P1363: Standard Specifications for Public-Key Cryptography
A (upcoming) standard for public key cryptography. Consists of several public key algorithms for encryption and digital signatures. Has a very thorough annex that goes through all necessary implementation details. See more at their homepage. - Publius Censor-Resistent Publishing Protocol
This is a very advanced system allowing a group of authors and readers to share documents on a set of web servers so that (1) no author or reader has to reveal his/her identity, (2) documents are certified to come from a certain (pseudonymous) author, (3) documents cannot be removed or modified (censored) unless a large amount of the involved web servers are compromised. Technical reports, software, and links to related projects can be found on their homepage. - Secure Shell
The Secure Shell version 2 protocol is developed by the IETF working group SecSh. This protocol is versatile for the needs of the Internet, and is currently used in the SSH Tectia software. The protocol is used to secure terminal sessions and arbitrary TCP connections. The Secure Shell v2 protocol is based on its predecessor Secure Shell v1 developed by Tatu Ylönen. The protocol specifications (RFCs 4250 to 4256) can be found from the IETF. - IPSec
While all the above protocols operate on the application layer of the internet, allowing particular programs to communicate on a secure channel in an inherently insecure network, IPSec attempts to make the internet secure in its essence, the internet protocol (IP). The IPSec protocols are defined in RFC 2401.
