random numbers and entropy

[stevenroose]

The ability to generate secure random numbers is extremely important when dealing with Bitcoin and has to be taken seriously. However, I've been pointed out that the Dart built-in random number generator is not very secure.

Also, I want to add the ability for developers to specify additional entropy sources for generating numbers, f.e. when they capture mouse movements from a user.

What I want to avoid is requiring that a random source is provided every time random number generation happens, so I've been thinking about providing a singleton class using which can be specified what entropy source will be used.

The cipher package provides some implementations of SRNG and entropy sources, so I'd probably use the interfaces from cipher.

In general, I'm no big fan of using singletons, that's why I put the idea here, maybe someone can come up with a different/better solution.