Fix and improve solo stamping

README.md

@@ -105,6 +105,19 @@ commitment operations and attestations in it:
         append 647b90ea1b270a97
         verify PendingAttestation('https://bob.btc.calendar.opentimestamps.org')
 
+### Timestamping without a calendar service with your own wallet
+
+It's possible to create a timestamp using your own Bitcoin Core wallet. This
+is generally not necessary, can harm your privacy and is somewhat risky because
+the code is not well tested.
+
+Use the `--btc-wallet` argument after `stamp` command to use this feature,
+optionally specifying a fee rate in sat/vbyte with `--fee-rate`. It is
+possible to RBF the resulting transaction and then resume the process using
+the `--txid` and `--nonce` arguments.
+
+See `ots stamp --help` for more info.
+
 ### Timestamping and Verifying PGP Signed Git Commits
 
 See `doc/git-integration.md`

otsclient/args.py

@@ -54,6 +54,9 @@ def make_common_options_arg_parser():
     btc_net_group.add_argument('--btc-testnet', dest='btc_net', action='store_const',
                                const='testnet', default='mainnet',
                                help='Use Bitcoin testnet rather than mainnet')
+    btc_net_group.add_argument('--btc-signet', dest='btc_net', action='store_const',
+                               const='signet', default='mainnet',
+                               help='Use Bitcoin signet rather than mainnet')
     btc_net_group.add_argument('--btc-regtest', dest='btc_net', action='store_const',
                                const='regtest',
                                help='Use Bitcoin regtest rather than mainnet')
@@ -135,6 +138,8 @@ def setup_bitcoin():
         """
         if args.btc_net == 'testnet':
            bitcoin.SelectParams('testnet')
+        elif args.btc_net == 'signet':
+           bitcoin.SelectParams('signet')
         elif args.btc_net == 'regtest':
            bitcoin.SelectParams('regtest')
         elif args.btc_net == 'mainnet':
@@ -169,6 +174,15 @@ def parse_ots_args(raw_args):
     parser_stamp.add_argument('-b', '--btc-wallet', dest='use_btc_wallet', action='store_true',
                               help='Create timestamp locally with the local Bitcoin wallet.')
 
+    parser_stamp.add_argument('-f', '--fee-rate', dest='fee_rate', default=False,
+                              help='Specify fee rate in sat/vbyte. Default is to let Bitcoin Core decide.')
+
+    parser_stamp.add_argument('--nonce', dest='nonce', default=False,
+                              help='Resume earlier stamp, must be used together with --txid')
+
+    parser_stamp.add_argument('--txid', dest='txid', default=False,
+                              help='Resume earlier stamp, must be used together with --nonce. Can be used with RBF.')
+
     parser_stamp.add_argument('files', metavar='FILE', type=argparse.FileType('rb'),
                               nargs='*',
                               help='Filename')
@@ -261,6 +275,11 @@ def parse_ots_args(raw_args):
         pass
 
     args = parser.parse_args(raw_args)
+
+    if hasattr(args, "nonce") or hasattr(args, "txid"):
+        if bool(args.nonce) ^ bool(args.txid):
+            parser_stamp.error('--nonce and --txid must be given together')
+
     args = handle_common_options(args, parser)
 
     return args

otsclient/cmds.py

@@ -45,7 +45,7 @@ def remote_calendar(calendar_uri):
                                                   user_agent="OpenTimestamps-Client/%s" % otsclient.__version__)
 
 
-def create_timestamp(timestamp, calendar_urls, args):
+def create_timestamp(timestamp, nonce, calendar_urls, args):
     """Create a timestamp
 
     calendar_urls - List of calendar's to use
@@ -57,18 +57,34 @@ def create_timestamp(timestamp, calendar_urls, args):
     if setup_bitcoin:
         proxy = setup_bitcoin()
 
-        unfunded_tx = CTransaction([], [CTxOut(0, CScript([OP_RETURN, timestamp.msg]))])
-        r = proxy.fundrawtransaction(unfunded_tx)  # FIXME: handle errors
-        funded_tx = r['tx']
+        txid = None
+        if args.txid:
+            logging.debug("Continue with existing transaction")
+            txid = bytes.fromhex(args.txid)[::-1]
+        else:
+            logging.debug("Call fundrawtransaction for OP_RETURN %s", timestamp.msg.hex())
+            unfunded_tx = CTransaction([], [CTxOut(0, CScript([OP_RETURN, timestamp.msg]))])
+
+            options = {}
+            if args.fee_rate:
+                options['fee_rate'] = args.fee_rate
+
+            r = proxy.fundrawtransaction(unfunded_tx, options)  # FIXME: handle errors
+            funded_tx = r['tx']
 
-        r = proxy.signrawtransaction(funded_tx)
-        assert r['complete']
-        signed_tx = r['tx']
+            logging.debug("Call signrawtransactionwithwallet %s", funded_tx.serialize().hex())
+            r = proxy.signrawtransactionwithwallet(funded_tx)
+            assert r['complete']
+            signed_tx = r['tx']
 
-        txid = proxy.sendrawtransaction(signed_tx)
-        logging.info('Sent timestamp tx')
+            logging.debug("Call sendrawtransaction %s", signed_tx.serialize().hex())
+            txid = proxy.sendrawtransaction(signed_tx)
+            logging.info('Sent timestamp tx')
 
         blockhash = None
+
+        logging.info('Waiting for confirmation. This can be interupted and resumed with:\nots stamp --nonce=%s --txid=%s', nonce.hex(), txid[::-1].hex())
+
         while blockhash is None:
             logging.info('Waiting for timestamp tx %s to confirm...' % b2lx(txid))
             time.sleep(1)
@@ -92,6 +108,10 @@ def create_timestamp(timestamp, calendar_urls, args):
         assert block_timestamp is not None
         timestamp.merge(block_timestamp)
 
+    # Do not use calendars when solo stamping:
+    if args.use_btc_wallet:
+        return True
+
     m = args.m
     n = len(calendar_urls)
     if m > n or m <= 0:
@@ -173,22 +193,23 @@ def stamp_command(args):
         # Remember that the files - and their timestamps - might get separated
         # later, so if we didn't use a nonce for every file, the timestamp
         # would leak information on the digests of adjacent files.
-        nonce_appended_stamp = file_timestamp.timestamp.ops.add(OpAppend(os.urandom(16)))
+        nonce = bytes.fromhex(args.nonce) if args.nonce else os.urandom(16)
+        nonce_appended_stamp = file_timestamp.timestamp.ops.add(OpAppend(nonce))
         merkle_root = nonce_appended_stamp.ops.add(OpSHA256())
 
         merkle_roots.append(merkle_root)
         file_timestamps.append(file_timestamp)
 
     merkle_tip = make_merkle_tree(merkle_roots)
 
-    if not args.calendar_urls:
+    if not args.use_btc_wallet or not args.calendar_urls:
         # Neither calendar nor wallet specified; add defaults
         args.calendar_urls.append('https://a.pool.opentimestamps.org')
         args.calendar_urls.append('https://b.pool.opentimestamps.org')
         args.calendar_urls.append('https://a.pool.eternitywall.com')
         args.calendar_urls.append('https://ots.btc.catallaxy.com')
 
-    create_timestamp(merkle_tip, args.calendar_urls, args)
+    create_timestamp(merkle_tip, nonce, args.calendar_urls, args)
 
     if args.wait:
         upgrade_timestamp(merkle_tip, args)