1 files changed, 838 insertions, 0 deletions

diff --git a/src/nostr.cpp b/src/nostr.cpp
new file mode 100644
index 0000000..8e2a07d
--- /dev/null
+++ b/src/nostr.cpp
@@ -0,0 +1,838 @@
+// Copyright (c) 2026 Bitflash developers
+// Distributed under the MIT/X11 software license.
+//
+// Peer discovery over Nostr relays. See nostr.h.
+
+#include "headers.h"
+#include <openssl/ssl.h>
+#include <openssl/err.h>
+// We link libsecp256k1 statically (without this the header assumes DLL import)
+#define SECP256K1_STATIC
+#include <secp256k1.h>
+#include <secp256k1_schnorrsig.h>
+#include <secp256k1_extrakeys.h>
+
+// util.h redefines snprintf as a macro (2009 MSVC compat); this breaks
+// nlohmann/json, which calls std::snprintf. Undo the macro just here.
+#ifdef snprintf
+#undef snprintf
+#endif
+#include <nlohmann/json.hpp>
+
+#include "btfaddr.h"
+#include "btfchan.h"
+
+using json = nlohmann::json;
+
+// Bitflash rendezvous descriptor: parameterized-replaceable Nostr event so each
+// node keeps exactly one current descriptor (keyed by author pubkey).
+static const int   BTF_DESC_KIND = 38501;
+// "-2" scopes the 2026 stable relaunch: new nodes discover only each other, and
+// the abandoned test .btf descriptors lingering on the relays become invisible.
+static const char* BTF_DESC_DTAG = "btf-descriptor-2";
+
+// Nostr network/scope for Bitflash. Events are replaceable (NIP-78).
+static const int   NOSTR_KIND   = 30078;
+static const char* NOSTR_DTAG   = "bitflash-mainnet-2";
+
+// Anonymous auto-discovery: how many peers to keep connected via .btf rendezvous
+// before we stop dialing more, and how many new dials to attempt per cycle.
+static const unsigned int BTF_TARGET_CONN   = 8;
+static const int          BTF_DIALS_PER_PASS = 4;
+
+// Other nodes' .btf addresses learned from their descriptors on the relays.
+static set<string> g_btfPeers;
+static CCriticalSection cs_btfPeers;
+
+// Public discovery relays. Tunable.
+const char* pszNostrRelays[] = {
+    "wss://relay.damus.io",
+    "wss://nos.lol",
+    "wss://relay.nostr.band",
+    "wss://relay.snort.social",
+};
+const int nNostrRelays = ARRAYLEN(pszNostrRelays);
+
+// Rendezvous meeting relay this node registers at (ThreadBtfAccept in net.cpp)
+// and advertises in its .btf descriptor. Seed default; /rvrelay overrides.
+string strBtfMeetingRelay = "90.156.222.107:8434";
+
+
+//
+// Utilities
+//
+static string HexEncode(const unsigned char* p, size_t n)
+{
+    static const char* h = "0123456789abcdef";
+    string s;
+    s.reserve(n * 2);
+    for (size_t i = 0; i < n; i++)
+    {
+        s += h[p[i] >> 4];
+        s += h[p[i] & 0xf];
+    }
+    return s;
+}
+
+static bool HexDecode(const string& s, unsigned char* out, size_t n)
+{
+    if (s.size() != n * 2)
+        return false;
+    for (size_t i = 0; i < n; i++)
+    {
+        unsigned int b;
+        if (sscanf(s.c_str() + i * 2, "%2x", &b) != 1)
+            return false;
+        out[i] = (unsigned char)b;
+    }
+    return true;
+}
+
+static string Base64Encode(const unsigned char* p, size_t n)
+{
+    static const char* tbl = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+    string s;
+    for (size_t i = 0; i < n; i += 3)
+    {
+        unsigned int b = p[i] << 16;
+        if (i + 1 < n) b |= p[i + 1] << 8;
+        if (i + 2 < n) b |= p[i + 2];
+        s += tbl[(b >> 18) & 0x3f];
+        s += tbl[(b >> 12) & 0x3f];
+        s += (i + 1 < n) ? tbl[(b >> 6) & 0x3f] : '=';
+        s += (i + 2 < n) ? tbl[b & 0x3f] : '=';
+    }
+    return s;
+}
+
+
+//
+// Node Nostr key -- secp256k1 x-only (BIP340), persisted in <appdir>/nostr.key
+//
+class CNostrKey
+{
+public:
+    secp256k1_context* ctx;
+    secp256k1_keypair  keypair;
+    unsigned char      seckey[32];   // node's secp256k1 secret (for descriptor signing)
+    unsigned char      xonly[32];    // node's x-only pubkey (also its .btf identity)
+    unsigned char      enc_pk[32];   // node's x25519 public key (echan `enc` field)
+    unsigned char      enc_sk[32];   // node's x25519 secret key
+    bool               fValid;
+
+    CNostrKey() : ctx(NULL), fValid(false) {}
+
+    ~CNostrKey()
+    {
+        if (ctx) secp256k1_context_destroy(ctx);
+    }
+
+    // Load or generate a 32-byte key persisted as hex in <appdir>/<name>.
+    static void LoadOrGenSecp(secp256k1_context* ctx, const string& file, unsigned char sk[32])
+    {
+        FILE* f = fopen(file.c_str(), "rb");
+        string strHex;
+        if (f) { char buf[65] = {0}; fread(buf, 1, 64, f); fclose(f); strHex = buf; }
+        if (!HexDecode(strHex, sk, 32) || !secp256k1_ec_seckey_verify(ctx, sk))
+        {
+            do { RAND_bytes(sk, sizeof(unsigned char) * 32); } while (!secp256k1_ec_seckey_verify(ctx, sk));
+            FILE* fw = fopen(file.c_str(), "wb");
+            if (fw) { string h = HexEncode(sk, 32); fwrite(h.c_str(), 1, h.size(), fw); fclose(fw); }
+        }
+    }
+
+    bool Init()
+    {
+        ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
+        if (!ctx)
+            return false;
+        unsigned char seed[32];
+        RAND_bytes(seed, sizeof(seed));
+        secp256k1_context_randomize(ctx, seed);
+
+        LoadOrGenSecp(ctx, GetAppDir() + "/nostr.key", seckey);
+
+        if (!secp256k1_keypair_create(ctx, &keypair, seckey))
+            return false;
+        secp256k1_xonly_pubkey xpub;
+        if (!secp256k1_keypair_xonly_pub(ctx, &xpub, NULL, &keypair))
+            return false;
+        secp256k1_xonly_pubkey_serialize(ctx, xonly, &xpub);
+
+        // x25519 encryption keypair for the end-to-end channel, persisted separately.
+        btf::ChanInit();
+        string strEncFile = GetAppDir() + "/btf_enc.key";
+        FILE* fe = fopen(strEncFile.c_str(), "rb");
+        bool fLoaded = false;
+        if (fe)
+        {
+            char buf[65] = {0};
+            if (fread(buf, 1, 64, fe) == 64 && HexDecode(string(buf), enc_sk, 32))
+                fLoaded = true;
+            fclose(fe);
+        }
+        if (fLoaded)
+        {
+            // Derive the public key from the stored secret (stable identity).
+            btf::ChanPublicFromSecret(enc_pk, enc_sk);
+        }
+        else
+        {
+            btf::ChanKeypair(enc_pk, enc_sk);
+            FILE* few = fopen(strEncFile.c_str(), "wb");
+            if (few) { string h = HexEncode(enc_sk, 32); fwrite(h.c_str(), 1, h.size(), few); fclose(few); }
+        }
+
+        fValid = true;
+        return true;
+    }
+
+    string PubKeyHex() const { return HexEncode(xonly, 32); }
+    string EncPubHex() const { return HexEncode(enc_pk, 32); }
+    string BtfAddress() const { return btf::Address(xonly); }
+
+    bool SignId(const unsigned char id[32], string& sigHexOut)
+    {
+        unsigned char sig[64];
+        unsigned char aux[32];
+        RAND_bytes(aux, sizeof(aux));
+        if (!secp256k1_schnorrsig_sign32(ctx, sig, id, &keypair, aux))
+            return false;
+        sigHexOut = HexEncode(sig, 64);
+        return true;
+    }
+};
+
+// The node's single Nostr/.btf identity, shared by the seeding thread here and
+// the rendezvous transport in net.cpp. Lazily initialized under a lock; the
+// secp256k1 context is immutable after Init, so concurrent use is safe.
+static CNostrKey g_nostrKey;
+static CCriticalSection cs_nostrKey;
+
+static bool EnsureNostrKey()
+{
+    CRITICAL_BLOCK(cs_nostrKey)
+        if (!g_nostrKey.fValid)
+            g_nostrKey.Init();
+    return g_nostrKey.fValid;
+}
+
+bool BtfGetIdentity(unsigned char pubkey[32], unsigned char enc_sk[32])
+{
+    if (!EnsureNostrKey())
+        return false;
+    memcpy(pubkey, g_nostrKey.xonly, 32);
+    memcpy(enc_sk, g_nostrKey.enc_sk, 32);
+    return true;
+}
+
+std::string BtfLocalAddress()
+{
+    if (!EnsureNostrKey())
+        return "";
+    return g_nostrKey.BtfAddress();
+}
+
+
+// Build and sign a Nostr event (NIP-01). Returns the event JSON.
+static bool BuildSignedEvent(CNostrKey& key, int kind, const json& tags,
+                             const string& content, json& eventOut)
+{
+    int64 created = GetTime();
+    // Canonical serialization for the id: [0,pubkey,created_at,kind,tags,content]
+    json ser = json::array({ 0, key.PubKeyHex(), created, kind, tags, content });
+    string s = ser.dump();
+
+    unsigned char id[32];
+    SHA256((const unsigned char*)s.data(), s.size(), id);
+
+    string sigHex;
+    if (!key.SignId(id, sigHex))
+        return false;
+
+    eventOut = json::object();
+    eventOut["id"]         = HexEncode(id, 32);
+    eventOut["pubkey"]     = key.PubKeyHex();
+    eventOut["created_at"] = created;
+    eventOut["kind"]       = kind;
+    eventOut["tags"]       = tags;
+    eventOut["content"]    = content;
+    eventOut["sig"]        = sigHex;
+    return true;
+}
+
+
+//
+// Minimal WebSocket client over TLS (wss) or TCP (ws), blocking with timeout.
+//
+class CWebSocket
+{
+public:
+    SOCKET     hSocket;
+    SSL_CTX*   sslctx;
+    SSL*       ssl;
+    bool       fTls;
+    string     recvbuf;
+
+    CWebSocket() : hSocket(INVALID_SOCKET), sslctx(NULL), ssl(NULL), fTls(false) {}
+    ~CWebSocket() { Close(); }
+
+    void Close()
+    {
+        if (ssl)    { SSL_shutdown(ssl); SSL_free(ssl); ssl = NULL; }
+        if (sslctx) { SSL_CTX_free(sslctx); sslctx = NULL; }
+        if (hSocket != INVALID_SOCKET) { closesocket(hSocket); hSocket = INVALID_SOCKET; }
+    }
+
+    int RawRead(char* buf, int len)
+    {
+        if (fTls) return SSL_read(ssl, buf, len);
+        return recv(hSocket, buf, len, 0);
+    }
+
+    bool RawWrite(const char* buf, int len)
+    {
+        int off = 0;
+        while (off < len)
+        {
+            int n = fTls ? SSL_write(ssl, buf + off, len - off)
+                         : send(hSocket, buf + off, len - off, 0);
+            if (n <= 0) return false;
+            off += n;
+        }
+        return true;
+    }
+
+    // Connect and perform the WebSocket handshake. url = wss://host[:port]/path
+    bool Connect(const string& url, int timeoutSec)
+    {
+        string u = url;
+        int port = 443;
+        fTls = true;
+        if (u.compare(0, 6, "wss://") == 0) { u = u.substr(6); fTls = true; port = 443; }
+        else if (u.compare(0, 5, "ws://") == 0) { u = u.substr(5); fTls = false; port = 80; }
+        else return false;
+
+        string host, path = "/";
+        size_t slash = u.find('/');
+        if (slash != string::npos) { host = u.substr(0, slash); path = u.substr(slash); }
+        else host = u;
+        size_t colon = host.find(':');
+        if (colon != string::npos) { port = atoi(host.substr(colon + 1).c_str()); host = host.substr(0, colon); }
+
+        // Resolve and connect (TCP)
+        struct addrinfo hints, *res = NULL;
+        memset(&hints, 0, sizeof(hints));
+        hints.ai_family = AF_INET;
+        hints.ai_socktype = SOCK_STREAM;
+        char portstr[16]; sprintf(portstr, "%d", port);
+        if (getaddrinfo(host.c_str(), portstr, &hints, &res) != 0 || !res)
+            return error("Nostr: getaddrinfo %s failed", host.c_str());
+        hSocket = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
+        if (hSocket == INVALID_SOCKET) { freeaddrinfo(res); return false; }
+
+        // Socket receive/send timeout: Windows takes a DWORD of milliseconds;
+        // POSIX takes a struct timeval.
+#ifdef _WIN32
+        DWORD tv = timeoutSec * 1000;
+        setsockopt(hSocket, SOL_SOCKET, SO_RCVTIMEO, (char*)&tv, sizeof(tv));
+        setsockopt(hSocket, SOL_SOCKET, SO_SNDTIMEO, (char*)&tv, sizeof(tv));
+#else
+        struct timeval tv;
+        tv.tv_sec = timeoutSec;
+        tv.tv_usec = 0;
+        setsockopt(hSocket, SOL_SOCKET, SO_RCVTIMEO, (char*)&tv, sizeof(tv));
+        setsockopt(hSocket, SOL_SOCKET, SO_SNDTIMEO, (char*)&tv, sizeof(tv));
+#endif
+
+        if (connect(hSocket, res->ai_addr, (int)res->ai_addrlen) != 0)
+        {
+            freeaddrinfo(res);
+            return error("Nostr: connect %s:%d failed", host.c_str(), port);
+        }
+        freeaddrinfo(res);
+
+        // TLS
+        if (fTls)
+        {
+            sslctx = SSL_CTX_new(TLS_client_method());
+            if (!sslctx) return false;
+            ssl = SSL_new(sslctx);
+            SSL_set_fd(ssl, (int)hSocket);
+            SSL_set_tlsext_host_name(ssl, host.c_str());  // SNI
+            if (SSL_connect(ssl) != 1)
+                return error("Nostr: TLS handshake with %s failed", host.c_str());
+        }
+
+        // WebSocket handshake (HTTP Upgrade)
+        unsigned char keybytes[16];
+        RAND_bytes(keybytes, sizeof(keybytes));
+        string wskey = Base64Encode(keybytes, sizeof(keybytes));
+        string req =
+            "GET " + path + " HTTP/1.1\r\n"
+            "Host: " + host + "\r\n"
+            "Upgrade: websocket\r\n"
+            "Connection: Upgrade\r\n"
+            "Sec-WebSocket-Key: " + wskey + "\r\n"
+            "Sec-WebSocket-Version: 13\r\n\r\n";
+        if (!RawWrite(req.data(), (int)req.size()))
+            return false;
+
+        // Read the handshake response until \r\n\r\n
+        string resp;
+        char c;
+        while (resp.find("\r\n\r\n") == string::npos)
+        {
+            int n = RawRead(&c, 1);
+            if (n <= 0) return error("Nostr: no handshake response from %s", host.c_str());
+            resp += c;
+            if (resp.size() > 4096) break;
+        }
+        if (resp.find(" 101 ") == string::npos)
+            return error("Nostr: handshake refused by %s", host.c_str());
+        return true;
+    }
+
+    // Send a text message (masked frame, as required by the protocol)
+    bool SendText(const string& msg)
+    {
+        string frame;
+        frame += (char)0x81; // FIN + opcode texto
+        size_t len = msg.size();
+        if (len < 126)
+            frame += (char)(0x80 | len);
+        else if (len <= 0xffff)
+        {
+            frame += (char)(0x80 | 126);
+            frame += (char)((len >> 8) & 0xff);
+            frame += (char)(len & 0xff);
+        }
+        else
+        {
+            frame += (char)(0x80 | 127);
+            for (int i = 7; i >= 0; i--) frame += (char)((len >> (8 * i)) & 0xff);
+        }
+        unsigned char mask[4];
+        RAND_bytes(mask, 4);
+        frame.append((char*)mask, 4);
+        string masked = msg;
+        for (size_t i = 0; i < masked.size(); i++)
+            masked[i] ^= mask[i & 3];
+        frame += masked;
+        return RawWrite(frame.data(), (int)frame.size());
+    }
+
+    // Receive the next complete text message. Returns false on error/timeout.
+    bool RecvText(string& out)
+    {
+        out.clear();
+        for (;;)
+        {
+            unsigned char hdr[2];
+            if (!ReadN((char*)hdr, 2)) return false;
+            bool fin = hdr[0] & 0x80;
+            int opcode = hdr[0] & 0x0f;
+            bool masked = hdr[1] & 0x80;
+            uint64 len = hdr[1] & 0x7f;
+            if (len == 126)
+            {
+                unsigned char e[2];
+                if (!ReadN((char*)e, 2)) return false;
+                len = (e[0] << 8) | e[1];
+            }
+            else if (len == 127)
+            {
+                unsigned char e[8];
+                if (!ReadN((char*)e, 8)) return false;
+                len = 0;
+                for (int i = 0; i < 8; i++) len = (len << 8) | e[i];
+            }
+            unsigned char mask[4] = {0,0,0,0};
+            if (masked && !ReadN((char*)mask, 4)) return false;
+
+            string payload;
+            payload.resize((size_t)len);
+            if (len && !ReadN(&payload[0], (int)len)) return false;
+            if (masked)
+                for (size_t i = 0; i < payload.size(); i++)
+                    payload[i] ^= mask[i & 3];
+
+            if (opcode == 0x8) return false;                 // close
+            if (opcode == 0x9) { SendPong(payload); continue; } // ping
+            if (opcode == 0xA) continue;                      // pong
+            out += payload;                                   // text/continuation
+            if (fin) return true;
+        }
+    }
+
+private:
+    bool ReadN(char* buf, int n)
+    {
+        int off = 0;
+        while (off < n)
+        {
+            int r = RawRead(buf + off, n - off);
+            if (r <= 0) return false;
+            off += r;
+        }
+        return true;
+    }
+
+    void SendPong(const string& payload)
+    {
+        string frame;
+        frame += (char)0x8A;
+        frame += (char)(0x80 | (payload.size() & 0x7f));
+        unsigned char mask[4]; RAND_bytes(mask, 4);
+        frame.append((char*)mask, 4);
+        string m = payload;
+        for (size_t i = 0; i < m.size(); i++) m[i] ^= mask[i & 3];
+        frame += m;
+        RawWrite(frame.data(), (int)frame.size());
+    }
+};
+
+
+// Handle a received event: extract "ip:port" and register the address.
+static void HandlePeerEvent(const json& ev)
+{
+    if (!ev.contains("content")) return;
+    string content = ev["content"].get<string>();
+    // expected content: "ip:port"
+    CAddress addr(content.c_str());
+    if (addr.ip == 0 || addr.ip == INADDR_NONE)
+        return;
+    if (addr.ip == addrLocalHost.ip && addr.port == addrLocalHost.port)
+        return; // not ourselves (same ip:port)
+    // Peer received from the relay (before AddAddress's routability filter).
+    printf("Nostr: peer received from relay: %s\n", addr.ToStringIPPort().c_str());
+    CAddrDB addrdb;
+    if (AddAddress(addrdb, addr))
+        printf("Nostr: new peer added %s\n", addr.ToStringIPPort().c_str());
+}
+
+
+// Publish this node's self-certifying `.btf` descriptor: "reach me (this key)
+// via <meeting_node>, encrypting to my x25519 key <enc>". Signed by the node
+// key so only the address's owner can publish it (no hijacking).
+static void PublishDescriptor(CWebSocket& ws, CNostrKey& key)
+{
+    // meeting_node is the rendezvous relay this node's hidden service
+    // (ThreadBtfAccept in net.cpp) is registered at -- where clients dial us.
+    string meeting_node = strBtfMeetingRelay.empty() ? "rendezvous-pending"
+                                                     : strBtfMeetingRelay;
+    string desc = btf::SignDescriptor(key.ctx, key.seckey, key.EncPubHex(),
+                                      meeting_node, (uint64_t)GetTime());
+    if (desc.empty())
+        return;
+    json tags = json::array({ json::array({ "d", BTF_DESC_DTAG }) });
+    json ev;
+    if (BuildSignedEvent(key, BTF_DESC_KIND, tags, desc, ev))
+    {
+        json pub = json::array({ "EVENT", ev });
+        ws.SendText(pub.dump());
+    }
+}
+
+// Resolve a `.btf` address via a relay: fetch the descriptor published by that
+// address's key and verify it self-certifies under the decoded pubkey.
+static bool ResolveDescriptor(CWebSocket& ws, void* ctx, const string& btfAddr,
+                              btf::Descriptor& out)
+{
+    unsigned char pk[32];
+    if (!btf::ParseAddress(btfAddr, pk))
+        return false;
+    json filter = json::object();
+    filter["authors"] = json::array({ HexEncode(pk, 32) });
+    filter["kinds"]   = json::array({ BTF_DESC_KIND });
+    filter["limit"]   = 1;
+    json req = json::array({ "REQ", "btf-resolve", filter });
+    if (!ws.SendText(req.dump()))
+        return false;
+    for (;;)
+    {
+        string msg;
+        if (!ws.RecvText(msg))
+            break;
+        json j;
+        try { j = json::parse(msg); } catch (...) { continue; }
+        if (!j.is_array() || j.empty()) continue;
+        string t = j[0].get<string>();
+        if (t == "EVENT" && j.size() >= 3)
+        {
+            const json& ev = j[2];
+            if (ev.contains("content") &&
+                btf::VerifyDescriptor(ctx, ev["content"].get<string>(), pk, out))
+                return true;
+        }
+        else if (t == "EOSE")
+            break;
+    }
+    return false;
+}
+
+// Resolve a `.btf` address into its rendezvous coordinates by querying the
+// public discovery relays for the owner's self-certified descriptor. Used by
+// ConnectNodeBtf in net.cpp.
+bool BtfResolve(const std::string& btfAddr, std::string& meetingHostPort,
+                unsigned char enc_pub[32])
+{
+    if (!EnsureNostrKey())
+        return false;
+    for (int i = 0; i < nNostrRelays && !fShutdown; i++)
+    {
+        try
+        {
+            CWebSocket ws;
+            if (!ws.Connect(pszNostrRelays[i], 10))
+                continue;
+            btf::Descriptor d;
+            if (!ResolveDescriptor(ws, g_nostrKey.ctx, btfAddr, d))
+                continue;
+            if (d.meeting_node.empty() || d.meeting_node == "rendezvous-pending")
+                continue; // descriptor predates the owner's relay config
+            if (!HexDecode(d.enc, enc_pub, 32))
+                continue;
+            meetingHostPort = d.meeting_node;
+            return true;
+        }
+        CATCH_PRINT_EXCEPTION("BtfResolve")
+    }
+    return false;
+}
+
+
+// Connect to a relay: publish our address and collect the others'.
+static bool SeedFromRelay(CNostrKey& key, const string& relay)
+{
+    CWebSocket ws;
+    if (!ws.Connect(relay, 10))
+        return false;
+    printf("Nostr: connected to %s\n", relay.c_str());
+
+    // Publish our announcement (replaceable event with our ip:port)
+    if (addrLocalHost.ip != 0)
+    {
+        json tags = json::array({
+            json::array({ "d", NOSTR_DTAG }),
+            json::array({ "t", NOSTR_DTAG })
+        });
+        json ev;
+        if (BuildSignedEvent(key, NOSTR_KIND, tags, addrLocalHost.ToStringIPPort(), ev))
+        {
+            json pub = json::array({ "EVENT", ev });
+            ws.SendText(pub.dump());
+        }
+    }
+
+    // Publish our self-certifying .btf descriptor (rendezvous discovery)
+    PublishDescriptor(ws, key);
+
+    // Subscribe to receive the announcements of other nodes
+    json filter = json::object();
+    filter["kinds"] = json::array({ NOSTR_KIND });
+    filter["#d"]    = json::array({ NOSTR_DTAG });
+    filter["limit"] = 500;
+    json req = json::array({ "REQ", "bf-sub", filter });
+    if (!ws.SendText(req.dump()))
+        return false;
+
+    // Read responses until EOSE (end of stored events) or timeout
+    int nEvents = 0;
+    for (;;)
+    {
+        string msg;
+        if (!ws.RecvText(msg))
+            break; // timeout or closed connection
+        json j;
+        try { j = json::parse(msg); } catch (...) { continue; }
+        if (!j.is_array() || j.empty()) continue;
+        string type = j[0].get<string>();
+        if (type == "EVENT" && j.size() >= 3)
+        {
+            HandlePeerEvent(j[2]);
+            if (++nEvents > 1000) break;
+        }
+        else if (type == "EOSE")
+        {
+            // We received all stored events; close this relay.
+            break;
+        }
+        else if (type == "NOTICE" || type == "OK" || type == "CLOSED")
+        {
+            // informational
+        }
+    }
+    printf("Nostr: %s returned %d events\n", relay.c_str(), nEvents);
+
+    // Discover other nodes' .btf descriptors so we can auto-connect anonymously
+    // (no manual /connectbtf). Each node publishes one addressable descriptor
+    // (kind 38501, d-tag btf-descriptor); we learn every peer's .btf address by
+    // deriving it from the event author. Reachability is verified later, when
+    // the rendezvous tunnel boxes to that key's static x25519 key.
+    ws.SendText(json::array({ "CLOSE", "bf-sub" }).dump());
+    {
+        json dfilter = json::object();
+        dfilter["kinds"] = json::array({ BTF_DESC_KIND });
+        dfilter["#d"]    = json::array({ BTF_DESC_DTAG });
+        dfilter["limit"] = 200;
+        json dreq = json::array({ "REQ", "btf-disc", dfilter });
+        int nPeers = 0;
+        if (ws.SendText(dreq.dump()))
+        {
+            for (;;)
+            {
+                string msg;
+                if (!ws.RecvText(msg))
+                    break;
+                json j;
+                try { j = json::parse(msg); } catch (...) { continue; }
+                if (!j.is_array() || j.empty()) continue;
+                string type = j[0].get<string>();
+                if (type == "EVENT" && j.size() >= 3)
+                {
+                    const json& ev = j[2];
+                    if (!ev.contains("pubkey") || !ev.contains("kind")) continue;
+                    if (ev["kind"].get<int>() != BTF_DESC_KIND) continue;
+                    unsigned char pkb[32];
+                    if (!HexDecode(ev["pubkey"].get<string>(), pkb, 32)) continue;
+                    if (memcmp(pkb, key.xonly, 32) == 0) continue; // not ourselves
+                    string peerAddr = btf::Address(pkb);
+                    bool fNew = false;
+                    CRITICAL_BLOCK(cs_btfPeers)
+                        fNew = g_btfPeers.insert(peerAddr).second;
+                    if (fNew)
+                        printf("Nostr: discovered .btf peer %s\n", peerAddr.c_str());
+                    if (++nPeers > 500) break;
+                }
+                else if (type == "EOSE")
+                    break;
+            }
+        }
+    }
+    return true;
+}
+
+
+// Per-peer backoff: don't redial a .btf that just failed until this time. Keeps
+// dead/stale descriptors (e.g. abandoned test identities that linger on the
+// relays) from consuming the whole per-pass dial budget and starving the live
+// peers. Backoff grows on repeated failures, capped.
+static map<string, int64> g_btfPeerBackoff;   // addr -> next-try time
+static map<string, int>   g_btfPeerFails;      // addr -> consecutive failures
+
+// Dial the .btf peers discovered on the relays, up to a target connection count.
+// Mirrors ThreadOpenConnections' ref handling: a kept connection holds one ref
+// (owned by fNetworkNode, released on disconnect); a redundant one is released.
+static void ConnectDiscoveredBtfPeers()
+{
+    vector<string> peers;
+    CRITICAL_BLOCK(cs_btfPeers)
+        peers.assign(g_btfPeers.begin(), g_btfPeers.end());
+
+    // Shuffle: the candidate set is sorted, so without this a handful of dead
+    // peers at the front would be retried every pass and the live peers further
+    // down the list would never be reached within the per-pass dial budget.
+    for (size_t i = peers.size(); i > 1; i--)
+        swap(peers[i - 1], peers[(size_t)GetRand(i)]);
+
+    int64 now = GetTime();
+    int nDials = 0;
+    foreach(const string& addr, peers)
+    {
+        if (fShutdown) break;
+        if (vNodes.size() >= BTF_TARGET_CONN) break;
+        if (nDials >= BTF_DIALS_PER_PASS) break;
+
+        // Skip peers still in backoff from a recent failure.
+        map<string, int64>::iterator bi = g_btfPeerBackoff.find(addr);
+        if (bi != g_btfPeerBackoff.end() && now < bi->second)
+            continue;
+
+        CNode* pnode = ConnectNodeBtf(addr);
+        if (pnode)
+        {
+            if (!pnode->fNetworkNode)
+                pnode->fNetworkNode = true; // keep the ref from ConnectNodeBtf
+            else
+                pnode->Release();           // already connected; drop the extra ref
+            g_btfPeerBackoff.erase(addr);   // reachable again
+            g_btfPeerFails.erase(addr);
+        }
+        else
+        {
+            // Exponential-ish backoff: 1,2,4,... minutes, capped at 30.
+            int n = ++g_btfPeerFails[addr];
+            int64 mins = 1;
+            for (int k = 1; k < n && mins < 30; k++) mins *= 2;
+            if (mins > 30) mins = 30;
+            g_btfPeerBackoff[addr] = now + mins * 60;
+            nDials++; // only count real (failed) dial attempts against the budget
+        }
+    }
+}
+
+
+void ThreadNostrSeed(void* parg)
+{
+    printf("ThreadNostrSeed started\n");
+
+    if (!EnsureNostrKey())
+    {
+        printf("Nostr: failed to initialize secp256k1 key\n");
+        return;
+    }
+    CNostrKey& key = g_nostrKey;
+    printf("Nostr: node pubkey = %s\n", key.PubKeyHex().c_str());
+    printf("Nostr: node .btf address = %s\n", key.BtfAddress().c_str());
+
+    // One-time self-test of the rendezvous: publish our descriptor to a relay,
+    // then resolve our OWN .btf address back and verify it self-certifies. Proves
+    // the .btf publish/resolve/verify chain works against real public relays.
+    for (int i = 0; i < nNostrRelays && !fShutdown; i++)
+    {
+        try
+        {
+            CWebSocket ws;
+            if (!ws.Connect(pszNostrRelays[i], 10)) continue;
+            PublishDescriptor(ws, key);
+            Sleep(700); // let the relay store the replaceable event
+            btf::Descriptor d;
+            if (ResolveDescriptor(ws, key.ctx, key.BtfAddress(), d))
+            {
+                printf("Nostr: .btf self-resolve OK via %s (meeting_node=%s, enc=%s...)\n",
+                       pszNostrRelays[i], d.meeting_node.c_str(), d.enc.substr(0, 16).c_str());
+                break;
+            }
+        }
+        CATCH_PRINT_EXCEPTION("btf self-test")
+    }
+
+    // OpenSSL is already initialized by the rest of the app; TLS_client_method is enough.
+    loop
+    {
+        for (int i = 0; i < nNostrRelays; i++)
+        {
+            if (fShutdown) return;
+            try
+            {
+                SeedFromRelay(key, pszNostrRelays[i]);
+            }
+            CATCH_PRINT_EXCEPTION("SeedFromRelay")
+        }
+
+        // Auto-connect to discovered .btf peers over the rendezvous relay -- the
+        // anonymous, CGNAT-friendly replacement for the old IP-based connect. No
+        // manual /connectbtf needed: nodes find each other purely via Nostr.
+        try
+        {
+            ConnectDiscoveredBtfPeers();
+        }
+        CATCH_PRINT_EXCEPTION("ConnectDiscoveredBtfPeers")
+
+        // Re-announce/re-discover periodically (the replaceable event keeps the
+        // relay up to date and picks up nodes that joined after us)
+        for (int i = 0; i < 60 && !fShutdown; i++)
+            Sleep(1000);
+    }
+}