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pragma solidity ^0.4.24;
/**
* @title Elliptic curve signature operations
* @dev Based on https://gist.github.com/axic/5b33912c6f61ae6fd96d6c4a47afde6d
* TODO Remove this library once solidity supports passing a signature to ecrecover.
* See https://github.com/ethereum/solidity/issues/864
*/
library ECDSA {
/**
* @dev Recover signer address from a message by using their signature
* @param hash bytes32 message, the hash is the signed message. What is recovered is the signer address.
* @param signature bytes signature, the signature is generated using web3.eth.sign()
*/
function recover(bytes32 hash, bytes signature) internal pure returns (address) {
bytes32 r;
bytes32 s;
uint8 v;
// Check the signature length
if (signature.length != 65) {
return (address(0));
}
// Divide the signature in r, s and v variables
// ecrecover takes the signature parameters, and the only way to get them
// currently is to use assembly.
// solium-disable-next-line security/no-inline-assembly
assembly {
r := mload(add(signature, 0x20))
s := mload(add(signature, 0x40))
v := byte(0, mload(add(signature, 0x60)))
}
// Version of signature should be 27 or 28, but 0 and 1 are also possible versions
if (v < 27) {
v += 27;
}
// If the version is correct return the signer address
if (v != 27 && v != 28) {
return (address(0));
} else {
// solium-disable-next-line arg-overflow
return ecrecover(hash, v, r, s);
}
}
/**
* toEthSignedMessageHash
* @dev prefix a bytes32 value with "\x19Ethereum Signed Message:"
* and hash the result
*/
function toEthSignedMessageHash(bytes32 hash) internal pure returns (bytes32) {
// 32 is the length in bytes of hash,
// enforced by the type signature above
return keccak256(abi.encodePacked("\x19Ethereum Signed Message:\n32", hash));
}
}