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proprietary APIs are also used by vendors to safeguard their technical investments. Even within these closed environments, APIs provide a major technical and business benefit for those vendors licensed to develop products using that API. For example, Novell was one of the first network operating system vendors to make extensive use of an API to support a wide range of add-on products.  Under its approach, a "netware" loadable module (NLM) can be developed by a third-party developer and incorporated into an operational system by the user. The use of a proprietary API allows vendors to maintain the quality of third party products, to provide a basis for the development of niche products, and to maintain a competitive advantage. In Novell's case, the development of NLMs for major database products has boosted its sales in that competitive server market.

Perhaps the most common API today is Microsoft's object linking and embedding (OLE) software technology, which provides general-purpose sockets for modules that can undertake many different functions. For example, an OLE socket can provide the user with the capability to insert a module for file encryption or for file compression. Thus, although it might be possible to use government regulations to prevent the widespread use of sockets for encryption, it would be difficult to dampen the spread of a general-purpose socket that has many uses. OLE interfaces could plausibly support some level of encryption capability; however, since OLE interfaces are not specifically designed for security, they may have weaknesses that render them unsuitable for security-specific applications.

A cryptographic applications programming interface (CAPI) is an API specifically designed to support the introduction of cryptographic functions into products. It is not necessary to actually provide the cryptographic functions when the system is initially sold. Users would then be able to incorporate the cryptographic add-ons of their choice. Technically, a CAPI would provide an interface to a set of cryptographic services; it would usually include authentication, digital signature generation, random number generation, and stream or block mode encryption. Although there are some technical problems specific to CAPIs, most notably those associated with ensuring the integrity of the security processing, they exhibit, for the most part, the same advantages as any other API. That is, there are strong technical and business reasons for incorporating a CAPI into open systems.

CAPIs would enable applications developers to take for granted the existence of cryptographic functionality and not have to provide for such functionality themselves. Moreover, by separating the cryptography from the baseline product, major system vendors will be able to make changes

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