Bitflash: fair-launch release

Satoshi's bitcoin-0.1.0 reborn with RandomX CPU proof of work, anonymous .btf
addressing over Nostr with CGNAT rendezvous, automatic peer discovery, a
headless Linux node, and Windows GUI wallet. Fair launch, no premine, 21M cap.

1 files changed, 59 insertions, 0 deletions

diff --git a/src/btfchan.h b/src/btfchan.h
new file mode 100644
index 0000000..7963f9d
--- /dev/null
+++ b/src/btfchan.h
@@ -0,0 +1,59 @@
+// Copyright (c) 2026 Bitflash developers
+// Distributed under the MIT/X11 software license.
+//
+// End-to-end encrypted channel for Bitflash (ported from the Itzal echan.rs).
+// Wraps a raw pipe in an authenticated stream so relays/rendezvous nodes see
+// only ciphertext and cannot MITM: only the endpoint holding the static secret
+// can derive the key.
+//
+// Handshake: the client makes an ephemeral X25519 key and sends its public half
+// to the endpoint. Both sides compute the same box (X25519 ECDH -> shared key
+// for XChaCha20-Poly1305, i.e. libsodium crypto_box). Wire frame:
+//   [len:4 BE][nonce:24][ciphertext || 16-byte tag]
+// with a fresh random 24-byte nonce per frame (safe to pick at random).
+
+#ifndef BITFLASH_BTFCHAN_H
+#define BITFLASH_BTFCHAN_H
+
+#include <vector>
+#include <stdint.h>
+#include <stddef.h>
+
+namespace btf
+{
+
+static const int CHAN_KEYBYTES   = 32; // X25519 public/secret and shared key
+static const int CHAN_NONCEBYTES = 24; // XChaCha20-Poly1305 nonce
+static const int CHAN_MACBYTES   = 16; // Poly1305 tag
+
+// Must be called once before any channel use (initializes libsodium). Idempotent.
+bool ChanInit();
+
+// Generate a static X25519 keypair (e.g. the endpoint's long-term key).
+void ChanKeypair(unsigned char pk[32], unsigned char sk[32]);
+
+// Derive the X25519 public key from a stored secret key (X25519 base mult).
+void ChanPublicFromSecret(unsigned char pk[32], const unsigned char sk[32]);
+
+// Client side: given the endpoint's static public key, produce an ephemeral
+// public key (to hand the endpoint) and the shared key. Returns false on error.
+bool ChanClientHandshake(const unsigned char endpoint_static_pub[32],
+                         unsigned char eph_pub_out[32], unsigned char shared_out[32]);
+
+// Endpoint side: rebuild the same shared key from the client's ephemeral public
+// key and my static secret. Only the static-secret holder can do this.
+bool ChanEndpointHandshake(const unsigned char client_eph_pub[32],
+                           const unsigned char my_static_sk[32], unsigned char shared_out[32]);
+
+// Encrypt a plaintext chunk into a full wire frame ([len][nonce][ct||tag]).
+std::vector<unsigned char> ChanEncryptFrame(const unsigned char shared[32],
+                                            const unsigned char* pt, size_t n);
+
+// Decrypt a frame BODY (nonce||ciphertext||tag, i.e. without the 4-byte length
+// prefix). Returns true and fills `out` on success; false on auth failure.
+bool ChanDecryptBody(const unsigned char shared[32],
+                     const unsigned char* body, size_t n, std::vector<unsigned char>& out);
+
+} // namespace btf
+
+#endif