Bitcoin utilizes a proof-of-work mechanism to assure against double-spending, as well as providing an example opensource implementation. However, some countries allow software patents, which could mean that one person/company has the ability to suddenly prevent the legal use of Satoshi Nakamoto's Bitcoin algorithms.

Are these Bitcoin algorithms complex enough to qualify for being patentable, and if so, in what countries might such patents be granted? Does this pose a significant legal risk for users of Bitcoin?