RanDAOs

RanDAO Simple

Don't generate random number, let's brute force it.

Idea

• Host think about a number, he will describe the number and ask Challengers to guess the result.
• Host take result from Challengers and remove previous description to make new description.
• Another Challengers will try to guess new result.
• Host pick 5 best results and combine them by using XOR operator.

Proof of Work & Zero-knowledge Proof

Create fingerprint

Blockhash is computed by miners and they have no idea what is it, until block has been found.

Host pick 128 bits from blockhash to create Fingerprint:

let Fingerprint = uint128(block.blockhash(block.number - 1))

All of above make sure that no one know about the Fingerprint before new block found.

Difficulty calculation

Difficulty was calculated by.

/*
Power shift left 16 bits OR with FINGERPRINT_LEN - Difference
The number with higher difference is a worst value.
FINGERPRINT_LEN equal to 128 bits
*/
let Difficulty = Power << 16 |FINGERPRINT_LEN - Difference 

It's mean Power is more effect to Difficulty value.

Process

Host create a campaign for anyone to submit answers.

RequireDifference & RequirePower is the requisites to the contributor submission effective ( accepted).

let Result = sha3(sha3(sha3(sha3(sha3(....sha3(Fingerprint + Key)))))) // Sha3 Power times

Challengers need to brute force Key and Power values.

Pick 128 bits from Result as a Snapshot:

set Snapshot = uint128(Result)

Compare Snapshot and current Fingerprint:

BitCompare(Snapshot, Fingerprint) <= RequireDiffrence && Power > RequirePower // Key and Power are accepted if following conditions are satisfy.

BitCompare() is the operation that comparing how many difference bits?.

We are try to find a half collision (the half-same numbers).

Challenger success to submit his submission

Challengers are need to deposit 10% of prize pool.

Fingerprint will be changed, after his submission is accepted.

let Fingerprint = Key >> FINGERPRINT_LEN // Remove old Fingerprint from new Fingerprint, last 128 bits

Difficulty will be increased to new Difficulty of submission.

let Difficulty = DifficultyCalculate(Power, difference)

No one able to predict because of the new Fingerprint is dependent on the results of previous calculations.

End

Pick 5 Keys from all contributors having highest Difficulty (which have geater Power and lower Difference bits): Keys[]

let Random = Keys[0] ^ Keys[1] ^ Keys[2] ^ Keys[3] ^ Keys[4] ^ Keys[5];
Random = Random >> FINGERPRINT_LEN;

Remove 128 bits of Fingerprint from Random, that will be the final result.