How can we generate multiple random number in ethereum?

Question

I want my smart contract to return 7 or 8 UNIQUE random numbers ranging from 1 to 100 upon calling the contract. What can be the best approach to obtain suc

Answer 1

Like Raghav said, random numbers on the blockchain are hard. The public nature of the network makes it very hard to generate a number that cannot be pre-calculated.

With that said, one of the best solutions is to use an oracle that gets the random number from an external (read: non-blockchain based) source. Take a look at this guide. The Ethtroll Dapp is a good example of this, so take a look at the code here. They use Oraclize to get a random number from Random.org.

An issue with using an oracle is the centralization factor. If you set up your Dapp in the way I have described above, you are at the mercy of a rouge employee at two different centralized services—Oraclize and Random.org. Though it would be unlikely for someone to manipulate either of these sources, people will perform irrational acts for potential economic gain.