Linked Questions
13 questions linked to/from When can BLOCKHASH be safely used for a random number? When would it be unsafe?
3
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1
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BlockHash used for random number generation [duplicate]
I am designing a lottery smart contract. A winning ticket number is drawn from a pool of tickets. In order to do this, I use the following code:
bytes32 blockhash = block.blockhash(block.number - 1);...
- 263
3
votes
1
answer
976
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Are future block hashes viable as an RNG? [duplicate]
Let's say I want to make a gambling contract. Anyone can call the createWager function to create a new bet to flip a coin. When they win, in order to collect the payment for the wager, they have to ...
- 33
3
votes
1
answer
477
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Risk of using BlockHash, other miners preventing attack. [duplicate]
When I read about the risk of using the blockhash as a random number it was explained to me the issue was that a miner can trow away the block if the block-hash is not in his advantage, and keeps ...
- 312
0
votes
1
answer
556
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Minereum Lucky Draw claims 100% Safe randomness on a smart contract without oracles, is it really possible? [duplicate]
Is the way Minereum Lucky Draw game works really safe 100% onchain RNG and verifiable on smart contract?
They claim yes but I would like to know expert technical answer for this, if so, isn't this a ...
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233
votes
20
answers
103k
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How can I securely generate a random number in my smart contract?
If I am writing a smart contract for some kind of (gambling) game, how can I generate a random number securely? What are the best practises and security trade-offs to be aware of?
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40
votes
3
answers
12k
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Can a contract safely rely on block.timestamp?
How safe is it to use block.timestamp as contract expiration time? If a miner provides an incorrect timestamp in a block header, how much can it be off before it is rejected by other nodes? Is there a ...
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5
votes
2
answers
3k
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Honest lottery winner generation - pseudo random number obtaining
Suppose I would like to organize a honest lottery and prevent cheating when we need to find a winner. I known problem of random number in the known network arises.
I would like to try the following ...
- 287
1
vote
1
answer
539
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Is this a safely design for a lottery smart contract? [closed]
I'm design a lottery smart contract. The lottery is like this:
the lottery will be drawed everyday;
24 hours of one day is split to active period(23 hours), freeze period(30 mins), and draw period(30 ...
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0
votes
2
answers
462
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How to generate randomness without external calls within a smart contract?
How can I generate a random number within the smart contract without external oracles. Maybe based on the block number or is there any other element that can be used for that?
2
votes
2
answers
171
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Where can I get feedback on how to improve my smart contract?
I built a fairly simple contract lottery that gives 20% of all proceedings to Give Directly, my favorite charity organization. I'd like to have someone who know what (s)he's doing to have a look at my ...
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2
votes
0
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248
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Can successive confirmation length blockhashes be used to generate an effective random number?
I've been trying to make a random number generator that doesn't need to be outsourced like Oraclize or break down at scale like RanDAO where n deposits gives 2^n possible manipulations for the random ...
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2
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0
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250
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How bad are future blockhashes as source of entropy exactly?
This is not a duplicate (see below)
Before you answer “bad, the miner can influence them”, please let me specify the question.
It’s clear that things like timestamp should not flow into a random ...
2
votes
1
answer
153
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Fair, barely malleable CSPRNG that can still be deterministic?
Just for fun, I wanted to start off making a test contract that generates ERC-20 tokens based off of prime length when in binary representation. I decided to use Rabin-Miller for the primality test, ...
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