How to safely generate a random number

Re:How to safely generate a random number by tptacek on Tuesday February 25, 2014 @09:53PM (#7302534)

If SecureRandom was simply "pull bytes from urandom" on Linux and "pull bytes from CryptGenRandom" on Windows, I wouldn't care enough to argue. But it's not. It's not even "pull bytes from urandom" on Linux; depending on the specific details of your platform, it can be dramatically different than that.

I'm absolutely not recommending that people write their own version of SecureRandom; I'm advising the opposite. Avoid userspace CSPRNGs. Use the system CSPRNG.

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Re:How to safely generate a random number by weavejester on Wednesday February 26, 2014 @04:45AM (#7303907)

So I should write my own cross-platform interface to the system PRNG? Doesn't that strike you as more prone to error than relying on SecureRandom, which at least has the advantage of having many eyes on it.

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Re:How to safely generate a random number by tptacek on Wednesday February 26, 2014 @11:41AM (#7305946)

NO. Relying on SecureRandom is riskier than writing the 5-10 lines of code it takes to read from urandom. Prefer urandom to SecureRandom.

Look what "many eyes" did for the Harmony PRNG.

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Re:How to safely generate a random number by weavejester on Wednesday February 26, 2014 @05:15PM (#7308461)

And urandom is not cross-platform, so if I were going to write a cross-platform library, how would you suggest doing it? By writing an interface to urandom, then an interface to CryptGenRandom (doesn't that require an FFI?), and then manually going through all of the platforms Java can potentially execute on until I can be sure I've covered all my bases?

I'm pretty sure that's going to be more than 5-10 lines of code.

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