Your friend is describing "poor man's copyright" or an "inventor's notebook," except done incorrectly. First, "poor man's copyright" is the wrongly-held belief

Your friend is describing "poor man's copyright" or an "inventor's notebook," except done incorrectly. First, "poor man's copyright" is the wrongly-held belief that you can mail yourself something, and the official postal service postmark will be proof enough that you wrote it when you said you did. This is not true, and will not hold up in a court of law. A much more easily forgeable email would hold up even less than not-at-all. Second, a patent, by definition, is a set of protections conferred in exchange for public disclosure. An actual patent requires enough detail that someone with a general understanding of whatever domain the patent is under could build your device, replicate your process, etc. In fact, publicly publishing not only the idea, but also the implementation, is the only defense against someone else filing a patent for it, as that establishes prior art. For paper publication, that means notarized copies of your "inventor's notebook:" http://en.wikipedia.org/wiki/Inventor%27s_notebook http://en.wikipedia.org/wiki/Inventor%27s_notebook You can also file for a patent and then abandon your application. Online publication is dicier unless you can get external proof that your publication dates are what you said they were (archive.org records, perhaps? other blogs citing you?). Because the US is the only(?) "first to invent" country (everyone else is first-to-file), you can more easily contest a patent by demonstrating that you were actively reducing it to practice (that replicable amount of detail again) before the filer was. Otherwise, you'd have to demonstrate that it was unpatentable instead: http://en.wikipedia.org/wiki/First_to_file_and_first_to_invent http://en.wikipedia.org/wiki/First_to_file_and_first_to_inve...