RC5 RSA Data Security's RC5 symmetric block cipher. Now an open standard and part of the Apache XML Project. X.500 Directory Services X.500 directory standards provide the basis for constructing multi-purpose distributed directory services by interconnecting computer systems belonging to service organizations, on a potentially global scale. The standard includes full specifications for data items required for X.500 to support the distribution of public key certificates together with a high level description of the surrounding management procedures. This is in the part of the standard designated X.509.
Directories are special purpose databases usually containing typed information.
They are distinguished from name services by their ability to search for, as well as retrieve, named information. Directory services are not suited to provide transaction-based services requiring huge number of updates. Nor should it be used for file storage, it is more sensible to store a pointer to a file in a directory rather than the file itself. A certificate is a collection of information to which a digital signature has been affixed by some authority that is recognised and trusted by some community of certificate users. In short, it confirms the entity is who or what it claims to be, and that the enclosed public key is theirs too.