Bitcoin Forum

Lots of interesting ideas are proposed using a publicly available source of random bits that everyone has access to. People have proposed using sunspots, etc. (See for example: Cryptography from Sunspots (http://www.cs.cornell.edu/~rafael/papers/cps07.pdf))

The requirement is that everyone should have access to a constant source of random stream of bits
There should be no disagreement on the bits selected. For instance I can say select bits from "now" to next 10 secs and everyone should have the same set of bits. Furthermore, I should not be able to predict the bits
 
Can we use the blockchain as a source of random bits?

The purpose of randomness (entropy) in cryptography is unpredictability. If everyone uses the same stream of random bits, then it is not secure because it is predictable. It's like always setting the seed of a PRNG to 0.

How about a lottery based on the bits a month from now at an exact time? Everybody can verify the validity of the lottery, without having to trust the lottery hoster. Sounds quite interesting to me.

Agree, blockchain is not as big as it would need to be to get random number from it.

If you want the same number of bits at any given time, then that's not really randomness. That's predefined, pretty much like a constant.

I'm thinking of using future blocks as a source of unpredictable randomness. Existing blocks are obviously not random anymore. Please browse through the paper "cryptography using sunspots" in the OP to understand what I'm getting at.