Passkey Support

[JeffreyDoyle]

No description provided.

[lmcmz]

Flow Protocol, including access node API and client SDKs must be updated to support sending, receiving and verifying transactions signatures using data that conforms to the Passkey specification.

Passkey signatures are performed by signing a payload which includes challenge, rpId to generate a signature (part of an "Public Key Credential" see here). Under Authenticator Assertion Response Object (see here), there are authenticatorData, clientDataJSON, userHandle and signature. To reconstruct the signed message, clientDataJSON and authenticatorData are SHA256 Hashed and combined as the actual signing payload. The ClientDataJSON has a variable length of challenge which can be used to include the existing Flow transaction encoding. Flow SDKs and Access Node API will need to be updated to support receiving both existing transaction payloads, along with clientDataJSON and authenticatorData to both support the existing signature format and that of the new Passkey standard.

Here is the example code to reconstruct signed message:

Data reconstructSignedMessage(const Data& authenticatorData, const Data& clientDataJSON) {
    const auto& clientHash = Hash::sha256(clientDataJSON);
    Data message;
    append(message, authenticatorData);
    append(message, clientHash);
    return Hash::sha256(message);
}

[KshitijChaudhary666]

Hi @JeffreyDoyle - This FLIP is not reflected on FLIP project tracker. Can you pls follow the process outlined in https://github.com/onflow/flips? Specifically the following would help show the FLIP on the project tracker-

• Create an issue by using one of the FLIP issue templates based on the type of the FLIP - application, governance, cadence or protocol
• The title of the issue should be the title of your FLIP, e.g., "Dynamic Inclusion fees". Submit the issue. Note the issue number that gets assigned
• Use the issue number generated in step 2 as the FLIP number on this PR. And mention the FLIP issue by copying the GitHub URL or the issue in the comment section here

Thank you!