src/get_file_hash_core/src/frost_mailbox_logic.rs on Nostr: #![cfg(feature = "nostr")] use frost_secp256k1_tr as frost; use ...

#![cfg(feature = "nostr")]

use frost_secp256k1_tr as frost;
use frost::keys::PublicKeyPackage;
use frost::round2::SignatureShare;
use frost::SigningPackage;
use hex;
use rand::thread_rng;
use std::collections::BTreeMap;
use sha2::Sha256;
use serde_json;
use sha2::Digest;

pub fn process_relay_share(
relay_payload_hex: &str,
signer_id_u16: u16,
_signing_package: &SigningPackage,
_pubkey_package: &PublicKeyPackage,
) -> Result<(), Box<dyn std::error::Error>> {
// In a real scenario, this function would deserialize the share, perform
// individual verification, and store it for aggregation.
// For this example, we'll just acknowledge receipt.
let _share_bytes = hex::decode(relay_payload_hex)?;
let _share = SignatureShare::deserialize(&_share_bytes)?;
let _identifier = frost::Identifier::try_from(signer_id_u16)?;

println!("✅ Share from Signer {} processed (simplified).", signer_id_u16);
Ok(())
}

pub fn simulate_frost_mailbox_coordinator() -> Result<(), Box<dyn std::error::Error>> {
let mut rng = thread_rng();
let (max_signers, min_signers) = (2, 2);

let (shares, pubkey_package) = frost::keys::generate_with_dealer(
max_signers,
min_signers,
frost::keys::IdentifierList::Default,
&mut rng,
)?;

let signer1_id = frost::Identifier::try_from(1 as u16)?;
let key_package1: frost::keys::KeyPackage = shares[&signer1_id].clone().try_into()?;
let signer2_id = frost::Identifier::try_from(2 as u16)?;
let key_package2: frost::keys::KeyPackage = shares[&signer2_id].clone().try_into()?;

let message = b"BIP-64MOD: Anchor Data Proposal v1";

let (nonces1, comms1) = frost::round1::commit(key_package1.signing_share(), &mut rng);
let (nonces2, comms2) = frost::round1::commit(key_package2.signing_share(), &mut rng);

let mut session_commitments = BTreeMap::new();
session_commitments.insert(signer1_id, comms1);
session_commitments.insert(signer2_id, comms2);

let signing_package = frost::SigningPackage::new(session_commitments.clone(), message);

let share1 = frost::round2::sign(&signing_package, &nonces1, &key_package1)?;
let share1_hex = hex::encode(share1.serialize());

let share2 = frost::round2::sign(&signing_package, &nonces2, &key_package2)?;
let share2_hex = hex::encode(share2.serialize());

println!("Coordinator listening for Nostr events (simulated)...");

process_relay_share(&share1_hex, 1_u16, &signing_package, &pubkey_package)?;
process_relay_share(&share2_hex, 2_u16, &signing_package, &pubkey_package)?;
println!("All required shares processed. Coordinator would now aggregate.");

Ok(())
}

/// Simulates a Signer producing a FROST signature share and preparing a Nostr event
/// to be sent to a coordinator via a "mailbox" relay.
///
/// In a real ROAST setup, signers would generate their share and post it
/// encrypted (e.g., using NIP-44) to a coordinator's "mailbox" on a Nostr relay.
/// This function demonstrates the creation of the signature share and the
/// construction of a *simplified* Nostr event JSON.
///
/// # Arguments
///
/// * `_identifier` - The FROST identifier of the signer. (Currently unused in this specific function body).
/// * `signing_package` - The FROST signing package received from the coordinator.
/// * `nonces` - The signer's nonces generated in Round 1.
/// * `key_package` - The signer's FROST key package.
/// * `coordinator_pubkey` - The hex-encoded public key of the ROAST coordinator,
/// used to tag the Nostr event.
///
/// # Returns
///
/// A `Result` containing the JSON string of the Nostr event if successful,
/// or a `Box<dyn std::error::Error>` if an error occurs.
pub fn create_signer_event(
_identifier: frost::Identifier,
signing_package: &frost::SigningPackage,
nonces: &frost::round1::SigningNonces,
key_package: &frost::keys::KeyPackage,
coordinator_pubkey: &str, // The Hex pubkey of the ROAST coordinator
) -> Result<String, Box<dyn std::error::Error>> {

// 1. Generate the partial signature share (Round 2 of FROST)
// This share is the core cryptographic output from the signer.
let share = frost::round2::sign(signing_package, nonces, key_package)?;
let share_bytes = share.serialize();
let share_hex = hex::encode(share_bytes);

// 2. Create a Session ID to tag the event
// This ID is derived from the signing package hash, allowing the coordinator
// to correlate shares belonging to the same signing session.
let mut hasher = Sha256::new();
hasher.update(signing_package.serialize()?);
let session_id = hex::encode(hasher.finalize());

// 3. Construct the Nostr Event JSON (Simplified)
// This JSON represents the event that a signer would post to a relay.
// In a production ROAST system, the 'content' field (the signature share)
// would be encrypted for the coordinator using NIP-44.
let event = serde_json::json!({
"kind": 4, // Example: Using Kind 4 (Private Message), though custom Kinds could be used for Sovereign Stack.
"pubkey": hex::encode(key_package.verifying_key().serialize()?.as_slice()), // Signer's public key
"created_at": 1712050000, // Example timestamp
"tags": [
["p", coordinator_pubkey], // 'p' tag: Directs the event to the coordinator.
["i", session_id], // 'i' tag: Provides a session identifier for filtering/requests.
["t", "frost-signature-share"] // 't' tag: A searchable label for the event type.
],
"content": share_hex, // The actual signature share (would be encrypted in production).
"id": "...", // Event ID (filled by relay upon publishing)
"sig": "..." // Event signature (filled by relay upon publishing)
});

Ok(event.to_string())
}

pub fn simulate_frost_mailbox_post_signer() -> Result<(), Box<dyn std::error::Error>> {
use rand::thread_rng;
use std::collections::BTreeMap;
use frost_secp256k1_tr as frost;

// This example simulates a single signer's role in a ROAST mailbox post workflow.
// The general workflow is:
// 1. Coordinator sends a request for signatures (e.g., on a BIP-64MOD proposal).
// 2. Signers receive the proposal, perform local verification.
// 3. Each signer generates their signature share and posts it (encrypted) to a
// Nostr relay, targeting the coordinator's mailbox.
// 4. The coordinator collects enough shares to aggregate the final signature.

let mut rng = thread_rng();
// For this example, we simulate a 2-of-2 threshold for simplicity.
let (max_signers, min_signers) = (2, 2);

////////////////////////////////////////////////////////////////////////////
// 1. Key Generation (Simulated Trusted Dealer)
////////////////////////////////////////////////////////////////////////////
// In a real distributed setup, this would be DKG. Here, a "trusted dealer"
// generates the shares and public key package.
let (shares, _pubkey_package) = frost::keys::generate_with_dealer(
max_signers,
min_signers,
frost::keys::IdentifierList::Default,
&mut rng,
)?;

// For a 2-of-2 scheme, we have two signers. Let's pick signer 1.
let signer1_id = frost::Identifier::try_from(1 as u16)?;
let key_package1: frost::keys::KeyPackage = shares[&signer1_id].clone().try_into()?;

let signer2_id = frost::Identifier::try_from(2 as u16)?;
let key_package2: frost::keys::KeyPackage = shares[&signer2_id].clone().try_into()?;

// The message that is to be signed (e.g., a hash of a Git commit or a Nostr event ID).
let message = b"This is a test message for ROAST mailbox post.";

////////////////////////////////////////////////////////////////////////////
// 2. Round 1: Commitment Phase (Signer's role)
////////////////////////////////////////////////////////////////////////////
// Each signer generates nonces and commitments.
let (nonces1, comms1) = frost::round1::commit(key_package1.signing_share(), &mut rng);
let (nonces2, comms2) = frost::round1::commit(key_package2.signing_share(), &mut rng);

// The coordinator collects these commitments. Here, we simulate by putting them in a BTreeMap.
let mut session_commitments = BTreeMap::new();
session_commitments.insert(signer1_id, comms1);
session_commitments.insert(signer2_id, comms2);

////////////////////////////////////////////////////////////////////////////
// 3. Signing Package Creation (Coordinator's role, simulated for context)
////////////////////////////////////////////////////////////////////////////
// The coordinator combines the collected commitments and the message to be signed
// into a signing package, which is then sent back to the signers.
let signing_package = frost::SigningPackage::new(session_commitments, message);

// Dummy coordinator public key. In a real scenario, this would be the
// actual public key of the ROAST coordinator, used for event tagging
// and encryption (NIP-44).
let coordinator_pubkey_hex = "0000000000000000000000000000000000000000000000000000000000000001";

////////////////////////////////////////////////////////////////////////////
// 4. Create the Signer Event (Signer's role)
////////////////////////////////////////////////////////////////////////////
// We demonstrate for signer 1. Signer 2 would perform a similar action.
let event_json_signer1 = create_signer_event(
signer1_id,
&signing_package,
&nonces1,
&key_package1,
coordinator_pubkey_hex,
)?;

println!("Generated Nostr Event for Signer 1 Mailbox Post:
{}", event_json_signer1);

// Similarly, Signer 2 would generate their event:
let event_json_signer2 = create_signer_event(
signer2_id,
&signing_package,
&nonces2,
&key_package2,
coordinator_pubkey_hex,
)?;
println!("Generated Nostr Event for Signer 2 Mailbox Post:
{}", event_json_signer2);

Ok(())
}