A pure Solidity implementation of elliptic curve secp256r1 / prime256v1 / p256.

The main purpose of this contract is verification of ECDSA signatures based on curve secp256r1 / prime256v1 / p256. To verify a signature, use the function

function validateSignature(bytes32 message, uint[2] memory rs, uint[2] memory Q) public pure
    returns (bool)

where

• bytes32 message is the hash of the signed message
• uint[2] rs contains the signature
• uint[2] Q contains the coordinates of the public key

The function returns true for valid signatures, false otherwise.

Notes:

• To disambiguate public keys when verifying signatures, activate condition rs[1] > lowSmax in validateSignature().
• To run the tests, first install the node packages (npm install) and then run truffle test.
• Verifying signatures is costly (!) in terms of gas.

• Tested with Solidity 0.5.0 and Truffle v5.0.1.
• Some newer versions of web3.js cause issues due to improper handling of bigNumber objects.
• Some components of the contract are based on code written by Andreas Olofsson, Alexander Vlasov (https://github.com/BANKEX/CurveArithmetics), and Avi Asayag (https://github.com/orbs-network/elliptic-curve-solidity).
• Versions of the contract have been deployed on the main Ethereum network (https://etherscan.io/address/0xf471789937856d80e589f5996cf8b0511ddd9de4) as well as the Ropsten test network (https://ropsten.etherscan.io/address/0x8025532f39e089d8bb3ed783ccdd974ee8c3948f).