This software is provided 'as-is', without any express or implied
warranty. In no event will Google be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, as long as the origin is not misrepresented.
original code is from http://android-developers.blogspot.jp/2013/08/some-securerandom-thoughts.html and license is as follows.
This software is provided 'as-is', without any express or implied warranty. In no event will Google be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, as long as the origin is not misrepresented.