The application programming interface (API) serves as an interface to a range of plug-in encryption modules that allow encryption algorithms to be added in a fairly transparent manner, so that adding a new algorithm or replacing an existing software implementation with custom encryption hardware can be done without any trouble. The standardised API allows any of the algorithms and modes supported by cryptlib to be used with a minimum of coding effort. In addition the easy-to-use high-level routines allow for the exchange of encrypted or signed messages or the establishment of secure communications channels with a minimum of programming overhead. Language bindings are available for C / C++, C# / .NET, Delphi, Java, Python, and Visual Basic (VB).
	cryptlib has been written to be as foolproof as possible. On initialisation it performs extensive self-testing against test data from encryption standards documents, and the APIs check each parameter and function call for errors before any actions are performed, with error reporting down to the level of individual parameters. In addition logical errors such as, for example, a key exchange function being called in the wrong sequence, are checked for and identified.
	cryptlib comes with extensive documentation in the form of a 330-page user manual and a 420-page technical reference manual. The user manual is intended for everyday cryptlib use and contains detailed documentation on every aspect of cryptlib's functionality. In most cases the code needed to secure an application can be cut and pasted directly from the appropriate section of the manual, avoiding the need to learn yet another programming API. The user manual concludes with a reference section covering the various cryptlib API functions, constants, and data types.
	The technical reference manual covers the design and internals of cryptlib itself, including the cryptlib security model and security mechanisms that protect every part of cryptlib.s operation. In addition the technical manual provides a wealth of background information to help users understand the security foundations on which cryptlib is built.
	cryptlib is re-entrant and completely thread-safe, allowing it to be used with multithreaded applications on systems that support threads. Because it is thread-safe, lengthy cryptlib operations can be run in the background if required while other processing is performed in the foreground. In addition cryptlib itself is multithreaded so that computationally intensive internal operations take place in the background without impacting the performance of the calling application.
	Most of the core algorithms used in cryptlib have been implemented in assembly language in order to provide the maximum possible performance, and will take advantage of crypto hardware acceleration facilities present in some CPUs such as the Via C3 family. These routines provide an unprecedented level of performance, in most cases running faster than expensive, specialised encryption hardware designed to perform the same task. This means that cryptlib can be used for high-bandwidth applications such as video/audio encryption and online network and disk encryption without the need to resort to expensive, specialised encryption hardware.