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Random Number Generation on VeChain
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| pragma solidity >=0.5.3 <=0.6.4; | |
| contract Extension { | |
| function blake2b256(bytes memory data) public view returns(bytes32); | |
| function blockID(uint num) public view returns(bytes32); | |
| function blockTotalScore(uint num) public view returns(uint64); | |
| function blockTime(uint num) public view returns(uint); | |
| function blockSigner(uint num) public view returns(address); | |
| function totalSupply() public view returns(uint256); | |
| function txProvedWork() public view returns(uint256); | |
| function txID() public view returns(bytes32); | |
| function txBlockRef() public view returns(bytes8); | |
| function txExpiration() public view returns(uint); | |
| } | |
| // bytes 32 = uint 256 | |
| // address = bytes 20 = uint 160 | |
| contract VeChainRandom { | |
| event RandomNumber(uint number); | |
| Extension en; | |
| // Get a random number | |
| // from a give block number | |
| function _getRandomNumber(uint top, uint _blockNumber) public returns (uint) { // get a number from [1, top] | |
| require(top > 1, "top > 1 required"); | |
| address extension_native = 0x0000000000000000000000457874656E73696F6e; | |
| en = Extension(extension_native); | |
| uint counter = 5; // How many previous blocks to take into consideration? | |
| uint256 s; | |
| for (uint i = 1; i < counter; i++) { | |
| uint256 s1 = uint256(en.blockSigner( (_blockNumber - i) )); | |
| s = s ^ (s1); | |
| uint256 s2 = uint256(en.blockID( (_blockNumber - i) )); | |
| s = s ^ (s2); | |
| } | |
| uint result = (s % top) + 1; | |
| emit RandomNumber(result); | |
| return result; | |
| } | |
| // Quickly get a random number | |
| // based on current block | |
| function quickRandomNumber(uint top) public returns (uint) { | |
| uint _blockNumber = block.number; | |
| return _getRandomNumber(top, _blockNumber); | |
| } | |
| } |
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