"It is in fact possible under certain circumstances to obtain an export license for software invoking cryptographic functions through an API. For example, Microsoft's implementation of the Microsoft Cryptographic API (CryptoAPI) specification was approved for export from the US, even though it implements an API by which third parties, including third parties outside the US, can add separate modules ("Cryptographic Service Providers" or CSPs) implementing cryptographic functionality. This export approval was presumably made possible because a) the CryptoAPI implementation requires third party CSPs to be digitally signed by Microsoft and rejects attempts to call CSPs not so signed; b) through this signing process Microsoft can ensure compliance with the relevant US export control regulations (e.g., they presumably would not sign a CSP developed outside the US that implements strong cryptography); and c) Microsoft's CryptoAPI implementation is available only in executable form, and thus is presumed to be reasonably resistant to user tampering to disable the CSP digital signature check."Microsoft stated that the second key is present as a backup to guard against the possibility of losing the primary secret key. Fernandes doubts this explanation, pointing out that the generally accepted way to guard against loss of a secret key is secret splitting, which would divide the key into several different parts, which would then be distributed throughout senior management. He stated that this would be far more robust than using two keys; if the second key is also lost, Microsoft would need to patch or upgrade every copy of Windows in the world, as well as every cryptographic module it had ever signed.