I know that the topic of random number has been discussed tremendous amount of times already but I have one small question.

I need to get a pseudo random number (not ungamealbe), as simply as possible. The problem is that I need the number to be either 1 or 0 and I want the value to be able to be odd or even in every loop iteration.

If I use something like:

while(x < 10) {
uint randomNumberBetween0And1 = uint(keccak256(abi.encodePacked(block.difficulty, now))) % 2;

this value will be either 10 times 0 (0 in each iteration because random number is even) or 10 x 1 (because random number will be odd every single time). How can I make the random differ between the iterations?

  • 1
    Hi there. If I'm understanding your question correctly, you could use the x variable as a nonce (as well as a loop counter), and incorporate it into what you pass to the keccak() call. Oct 8, 2018 at 17:57
  • Hey, thanks for anwser. In my case it's actually a while(true) kind of loop so I don't have x. Is there any way without the counter?
    – lemme
    Oct 8, 2018 at 18:27
  • 1
    just replace x<10 with true, but don't forget a break. However, you'll have to keep the counter, but that shouldn't be a problem?
    – ivicaa
    Oct 8, 2018 at 18:29

1 Answer 1


Try this:

while(x < 10) {
    uint rnd = uint(keccak256(block.difficulty, now, x)) & uint(0x1);

or if you have a while(true) as you wrote above:

uint x = 0;
while(true) {
    uint rnd = uint(keccak256(block.difficulty, now, x++)) & uint(0x1);

    ...YOUR CODE HERE hopefully with a condition for break...

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