Add the hardware signer compatibility (secp256r1)

[remiroyc]

Problem

The Bravos wallets use secure enclave and NIST-P256 elliptic curve (secp256r1) to sign messages. We must implement this signer in Cairo to verify the order proof and be filly compatible with this kind of wallets.

Feature request

The task here is to add a variant to the SignerValidator enum to support this: https://github.com/starkware-libs/cairo/blob/v2.3.1/corelib/src/starknet/secp256r1.cairo

impl SignerValidator of SignatureChecker {
    fn verify(hash: felt252, signer: Signer) -> felt252 {
        match signer {
            Signer::WEIERSTRESS_STARKNET(sign_info) => {
                let is_valid = ecdsa::check_ecdsa_signature(
                    hash, sign_info.user_pubkey, sign_info.user_sig_r, sign_info.user_sig_s
                );
                assert(is_valid, 'INVALID_SIGNATURE');
                sign_info.user_pubkey
            }
        }
    }
}

#[derive(Serde, Copy, Drop)]
enum Signer {
    WEIERSTRESS_STARKNET: SignInfo,
}

Links

https://braavos.app/hardware-signer-2fa-security-crypto-smart-contract-wallets/