Transaction

jMð]# OP_RETURN.py # # Python script to generate and retrieve OP_RETURN bitcoin transactions # # Copyright (c) Coin Sciences Ltd # # Permission is hereby granted, free of charge, to any person obtaining a copy # of this software and associated documentation files (the "Software"), to deal # in the Software without restriction, including without limitation the rights # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell # copies of the Software, and to permit persons to whom the Software is # furnished to do so, subject to the following conditions: # # The above copyright notice and this permission notice shall be included in # all copies or substantial portions of the Software. # # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN # THE SOFTWARE. import subprocess, json, time, random, os.path, binascii, struct, string, re, hashlib # Python 2-3 compatibility logic try: basestring except NameError: basestring = str # User-defined quasi-constants OP_RETURN_BITCOIN_IP='127.0.0.1' # IP address of your bitcoin node OP_RETURN_BITCOIN_USE_CMD=False # use command-line instead of JSON-RPC? CONF_FILE = '~/testnet.conf' if OP_RETURN_BITCOIN_USE_CMD: OP_RETURN_BITCOIN_PATH='/usr/bin/bitcoin-cli' # path to bitcoin-cli executable on this server else: OP_RETURN_BITCOIN_PORT='' # leave empty to use default port for mainnet/testnet OP_RETURN_BITCOIN_USER='' # leave empty to read from ~/.bitcoin/bitcoin.conf (Unix only) OP_RETURN_BITCOIN_PASSWORD='' # leave empty to read from ~/.bitcoin/bitcoin.conf (Unix only) OP_RETURN_BTC_FEE=0.003 # BTC fee to pay per transaction OP_RETURN_BTC_DUST=0.00001 # omit BTC outputs smaller than this OP_RETURN_MAX_BYTES=65535 # maximum bytes in an OP_RETURN (40 as of Bitcoin 0.10) OP_RETURN_MAX_BLOCKS=10 # maximum number of blocks to try when retrieving data OP_RETURN_NET_TIMEOUT=10 # how long to time out (in seconds) when communicating with bitcoin node # User-facing functions def OP_RETURN_send(send_address, send_amount, metadata, testnet=False): # Validate some parameters if not OP_RETURN_bitcoin_check(testnet): return {'error': 'Please check Bitcoin Core is running and OP_RETURN_BITCOIN_* constants are set correctly'} result=OP_RETURN_bitcoin_cmd('validateaddress', testnet, send_address) if not ('isvalid' in result and result['isvalid']): return {'error': 'Send address could not be validated: '+send_address} if isinstance(metadata, basestring): metadata=metadata.encode('utf-8') # convert to binary string metadata_len=len(metadata) if metadata_len>65536: return {'error': 'This library only supports metadata up to 65536 bytes in size'} if metadata_len>OP_RETURN_MAX_BYTES: return {'error': 'Metadata has '+str(metadata_len)+' bytes but is limited to '+str(OP_RETURN_MAX_BYTES)+' (see OP_RETURN_MAX_BYTES)'} # Calculate amounts and choose inputs output_amount=send_amount+OP_RETURN_BTC_FEE inputs_spend=OP_RETURN_select_inputs(output_amount, testnet) if 'error' in inputs_spend: return {'error': inputs_spend['error']} change_amount=inputs_spend['total']-output_amount # Build the raw transaction change_address=OP_RETURN_bitcoin_cmd('getrawchangeaddress', testnet) outputs={send_address: send_amount} if change_amount>=OP_RETURN_BTC_DUST: outputs[change_address]=change_amount raw_txn=OP_RETURN_create_txn(inputs_spend['inputs'], outputs, metadata, len(outputs), testnet) # Sign and send the transaction, return result return OP_RETURN_sign_send_txn(raw_txn, testnet) def OP_RETURN_store(data, testnet=False): # Data is stored in OP_RETURNs within a series of chained transactions. # If the OP_RETURN is followed by another output, the data continues in the transaction spending that output. # When the OP_RETURN is the last output, this also signifies the end of the data. # Validate parameters and get change address if not OP_RETURN_bitcoin_check(testnet): return {'error': 'Please check Bitcoin Core is running and OP_RETURN_BITCOIN_* constants are set correctly'} if isinstance(data, basestring): data=data.encode('utf-8') # convert to binary string data_len=len(data) if data_len==0: return {'error': 'Some data is required to be stored'} change_address=OP_RETURN_bitcoin_cmd('getrawchangeaddress', testnet) # Calculate amounts and choose first inputs to use output_amount=OP_RETURN_BTC_FEE*int((data_len+OP_RETURN_MAX_BYTES-1)/OP_RETURN_MAX_BYTES) # number of transactions required inputs_spend=OP_RETURN_select_inputs(output_amount, testnet) if 'error' in inputs_spend: return {'error': inputs_spend['error']} inputs=inputs_spend['inputs'] input_amount=inputs_spend['total'] # Find the current blockchain height and mempool txids height=int(OP_RETURN_bitcoin_cmd('getblockcount', testnet)) avoid_txids=OP_RETURN_bitcoin_cmd('getrawmempool', testnet) # Loop to build and send transactions result={'txids':[]} for data_ptr in range(0, data_len, OP_RETURN_MAX_BYTES): # Some preparation for this iteration last_txn=((data_ptr+OP_RETURN_MAX_BYTES)>=data_len) # is this the last tx in the chain? change_amount=input_amount-OP_RETURN_BTC_FEE metadata=data[data_ptr:data_ptr+OP_RETURN_MAX_BYTES] # Build and send this transaction outputs={} if change_amount>=OP_RETURN_BTC_DUST: # might be skipped for last transaction outputs[change_address]=change_amount raw_txn=OP_RETURN_create_txn(inputs, outputs, metadata, len(outputs) if last_txn else 0, testnet) send_result=OP_RETURN_sign_send_txn(raw_txn, testnet) # Check for errors and collect the txid if 'error' in send_result: result['error']=send_result['error'] break result['txids'].append(send_result['txid']) if data_ptr==0: result['ref']=OP_RETURN_calc_ref(height, send_result['txid'], avoid_txids) # Prepare inputs for next iteration inputs=[{ 'txid': send_result['txid'], 'vout': 1, }] input_amount=change_amount # Return the final result return result def OP_RETURN_retrieve(ref, max_results=1, testnet=False): # Validate parameters and get status of Bitcoin Core if not OP_RETURN_bitcoin_check(testnet): return {'error': 'Please check Bitcoin Core is running and OP_RETURN_BITCOIN_* constants are set correctly'} max_height=int(OP_RETURN_bitcoin_cmd('getblockcount', testnet)) heights=OP_RETURN_get_ref_heights(ref, max_height) if not isinstance(heights, list): return {'error': 'Ref is not valid'} # Collect and return the results results=[] for height in heights: if height==0: txids=OP_RETURN_list_mempool_txns(testnet) # if mempool, only get list for now (to save RPC calls) txns=None else: txns=OP_RETURN_get_block_txns(height, testnet) # if block, get all fully unpacked txids=txns.keys() for txid in txids: if OP_RETURN_match_ref_txid(ref, txid): if height==0: txn_unpacked=OP_RETURN_get_mempool_txn(txid, testnet) else: txn_unpacked=txns[txid] found=OP_RETURN_find_txn_data(txn_unpacked) if found: # Collect data from txid which matches ref and contains an OP_RETURN result={ 'txids': [str(txid)], 'data': found['op_return'], } key_heights={height: True} # Work out which other block heights / mempool we should try if height==0: try_heights=[] # nowhere else to look if first still in mempool else: result['ref']=OP_RETURN_calc_ref(height, txid, txns.keys()) try_heights=OP_RETURN_get_try_heights(height+1, max_height, False) # Collect the rest of the data, if appropriate if height==0: this_txns=OP_RETURN_get_mempool_txns(testnet) # now retrieve all to follow chain else: this_txns=txns last_txid=txid this_height=height while found['index'] < (len(txn_unpacked['vout'])-1): # this means more data to come next_txid=OP_RETURN_find_spent_txid(this_txns, last_txid, found['index']+1) # If we found the next txid in the data chain if next_txid: result['txids'].append(str(next_txid)) txn_unpacked=this_txns[next_txid] found=OP_RETURN_find_txn_data(txn_unpacked) if found: result['data']+=found['op_return'] key_heights[this_height]=True else: result['error']='Data incomplete - missing OP_RETURN' break last_txid=next_txid # Otherwise move on to the next height to keep looking else: if len(try_heights): this_height=try_heights.pop(0) if this_height==0: this_txns=OP_RETURN_get_mempool_txns(testnet) else: this_txns=OP_RETURN_get_block_txns(this_height, testnet) else: result['error']='Data incomplete - could not find next transaction' break # Finish up the information about this result result['heights']=list(key_heights.keys()) results.append(result) if len(results)>=max_results: break # stop if we have collected enough return results # Utility functions def OP_RETURN_select_inputs(total_amount, testnet): # List and sort unspent inputs by priority unspent_inputs=OP_RETURN_bitcoin_cmd('listunspent', testnet, 0) if not isinstance(unspent_inputs, list): return {'error': 'Could not retrieve list of unspent inputs'} unspent_inputs.sort(key=lambda unspent_input: unspent_input['amount']*unspent_input['confirmations'], reverse=True) # Identify which inputs should be spent inputs_spend=[] input_amount=0 for unspent_input in unspent_inputs: inputs_spend.append(unspent_input) input_amount+=unspent_input['amount'] if input_amount>=total_amount: break # stop when we have enough if input_amount<total_amount: return {'error': 'Not enough funds are available to cover the amount and fee'} # Return the successful result return { 'inputs': inputs_spend, 'total': input_amount, } def OP_RETURN_create_txn(inputs, outputs, metadata, metadata_pos, testnet): raw_txn=OP_RETURN_bitcoin_cmd('createrawtransaction', testnet, inputs, outputs) txn_unpacked=OP_RETURN_unpack_txn(OP_RETURN_hex_to_bin(raw_txn)) metadata_len=len(metadata) if metadata_len<=75: payload=bytearray((metadata_len,))+metadata # length byte + data (https://en.bitcoin.it/wiki/Script) elif metadata_len<=256: payload="\x4c"+bytearray((metadata_len,))+metadata # OP_PUSHDATA1 format else: payload="\x4d"+bytearray((metadata_len%256,))+bytearray((int(metadata_len/256),))+metadata # OP_PUSHDATA2 format metadata_pos=min(max(0, metadata_pos), len(txn_unpacked['vout'])) # constrain to valid values txn_unpacked['vout'][metadata_pos:metadata_pos]=[{ 'value': 0, 'scriptPubKey': '6a'+OP_RETURN_bin_to_hex(payload) # here's the OP_RETURN }] return OP_RETURN_bin_to_hex(OP_RETURN_pack_txn(txn_unpacked)) def OP_RETURN_sign_send_txn(raw_txn, testnet): signed_txn=OP_RETURN_bitcoin_cmd('signrawtransaction', testnet, raw_txn) if not ('complete' in signed_txn and signed_txn['complete']): return {'error': 'Could not sign the transaction'} send_txid=OP_RETURN_bitcoin_cmd('sendrawtransaction', testnet, signed_txn['hex']) if not (isinstance(send_txid, basestring) and len(send_txid)==64): return {'error': 'Could not send the transaction'} return {'txid': str(send_txid)} def OP_RETURN_list_mempool_txns(testnet): return OP_RETURN_bitcoin_cmd('getrawmempool', testnet) def OP_RETURN_get_mempool_txn(txid, testnet): raw_txn=OP_RETURN_bitcoin_cmd('getrawtransaction', testnet, txid) return OP_RETURN_unpack_txn(OP_RETURN_hex_to_bin(raw_txn)) def OP_RETURN_get_mempool_txns(testnet): txids=OP_RETURN_list_mempool_txns(testnet) txns={} for txid in txids: txns[txid]=OP_RETURN_get_mempool_txn(txid, testnet) return txns def OP_RETURN_get_raw_block(height, testnet): block_hash=OP_RETURN_bitcoin_cmd('getblockhash', testnet, height) if not (isinstance(block_hash, basestring) and len(block_hash)==64): return {'error': 'Block at height '+str(height)+' not found'} return { 'block': OP_RETURN_hex_to_bin(OP_RETURN_bitcoin_cmd('getblock', testnet, block_hash, False)) } def OP_RETURN_get_block_txns(height, testnet): raw_block=OP_RETURN_get_raw_block(height, testnet) if 'error' in raw_block: return {'error': raw_block['error']} block=OP_RETURN_unpack_block(raw_block['block']) return block['txs'] # Talking to bitcoin-cli def OP_RETURN_bitcoin_check(testnet): info=OP_RETURN_bitcoin_cmd('getinfo', testnet) return isinstance(info, dict) and 'balance' in info def OP_RETURN_bitcoin_cmd(command, testnet, *args): # more params are read from here if OP_RETURN_BITCOIN_USE_CMD: sub_args=[OP_RETURN_BITCOIN_PATH] if testnet: sub_args.append('-testnet') sub_args.append(command) for arg in args: sub_args.append(json.dumps(arg) if isinstance(arg, (dict, list, tuple)) else str(arg)) raw_result=subprocess.check_output(sub_args).decode("utf-8").rstrip("\n") try: # decode JSON if possible result=json.loads(raw_result) except ValueError: result=raw_result else: request={ 'id': str(time.time())+'-'+str(random.randint(100000,999999)), 'method': command, 'params': args, } port=OP_RETURN_BITCOIN_PORT user=OP_RETURN_BITCOIN_USER password=OP_RETURN_BITCOIN_PASSWORD if not (len(port) and len(user) and len(password)): #conf_lines=open(os.path.expanduser('~')+'/.bitcoin/bitcoin.conf').readlines() conf_lines=open(os.path.expanduser(CONF_FILE)).readlines() for conf_line in conf_lines: parts=conf_line.strip().split('=', 1) # up to 2 parts if (parts[0]=='rpcport') and not len(port): port=int(parts[1]) if (parts[0]=='rpcuser') and not len(user): user=parts[1] if (parts[0]=='rpcpassword') and not len(password): password=parts[1] if not len(port): port=18332 if testnet else 8332 if not (len(user) and len(password)): return None # no point trying in this case url='http://'+OP_RETURN_BITCOIN_IP+':'+str(port)+'/' try: from urllib2 import HTTPPasswordMgrWithDefaultRealm, HTTPBasicAuthHandler, build_opener, install_opener, urlopen, HTTPError except ImportError: from urllib.request import HTTPPasswordMgrWithDefaultRealm, HTTPBasicAuthHandler, build_opener, install_opener, urlopen passman=HTTPPasswordMgrWithDefaultRealm() passman.add_password(None, url, user, password) auth_handler=HTTPBasicAuthHandler(passman) opener=build_opener(auth_handler) install_opener(opener) try: raw_result=urlopen(url, json.dumps(request).encode('utf-8'), OP_RETURN_NET_TIMEOUT).read() except HTTPError as e: print e.fp.read() raise result_array=json.loads(raw_result.decode('utf-8')) result=result_array['result'] return result # Working with data references # The format of a data reference is: [estimated block height]-[partial txid] - where: # [estimated block height] is the block where the first transaction might appear and following # which all subsequent transactions are expected to appear. In the event of a weird blockchain # reorg, it is possible the first transaction might appear in a slightly earlier block. When # embedding data, we set [estimated block height] to 1+(the current block height). # [partial txid] contains 2 adjacent bytes from the txid, at a specific position in the txid: # 2*([partial txid] div 65536) gives the offset of the 2 adjacent bytes, between 0 and 28. # ([partial txid] mod 256) is the byte of the txid at that offset. # (([partial txid] mod 65536) div 256) is the byte of the txid at that offset plus one. # Note that the txid is ordered according to user presentation, not raw data in the block. def OP_RETURN_calc_ref(next_height, txid, avoid_txids): txid_binary=OP_RETURN_hex_to_bin(txid) for txid_offset in range(15): sub_txid=txid_binary[2*txid_offset:2*txid_offset+2] clashed=False for avoid_txid in avoid_txids: avoid_txid_binary=OP_RETURN_hex_to_bin(avoid_txid) if ( (avoid_txid_binary[2*txid_offset:2*txid_offset+2]==sub_txid) and (txid_binary!=avoid_txid_binary) ): clashed=True break if not clashed: break if clashed: # could not find a good reference return None tx_ref=ord(txid_binary[2*txid_offset:1+2*txid_offset])+256*ord(txid_binary[1+2*txid_offset:2+2*txid_offset])+65536*txid_offset return '%06d-%06d' % (next_height, tx_ref) def OP_RETURN_get_ref_parts(ref): if not re.search('^[0-9]+\-[0-9A-Fa-f]+$', ref): # also support partial txid for second half return None parts=ref.split('-') if re.search('[A-Fa-f]', parts[1]): if len(parts[1])>=4: txid_binary=OP_RETURN_hex_to_bin(parts[1][0:4]) parts[1]=ord(txid_binary[0:1])+256*ord(txid_binary[1:2])+65536*0 else: return None parts=list(map(int, parts)) if parts[1]>983039: # 14*65536+65535 return None return parts def OP_RETURN_get_ref_heights(ref, max_height): parts=OP_RETURN_get_ref_parts(ref) if not parts: return None return OP_RETURN_get_try_heights(parts[0], max_height, True) def OP_RETURN_get_try_heights(est_height, max_height, also_back): forward_height=est_height back_height=min(forward_height-1, max_height) heights=[] mempool=False try_height=0 while True: if also_back and ((try_height%3)==2): # step back every 3 tries heights.append(back_height) back_height-=1 else: if forward_height>max_height: if not mempool: heights.append(0) # indicates to try mempool mempool=True elif not also_back: break # nothing more to do here else: heights.append(forward_height) forward_height+=1 if len(heights)>=OP_RETURN_MAX_BLOCKS: break try_height+=1 return heights def OP_RETURN_match_ref_txid(ref, txid): parts=OP_RETURN_get_ref_parts(ref) if not parts: return None txid_offset=int(parts[1]/65536) txid_binary=OP_RETURN_hex_to_bin(txid) txid_part=txid_binary[2*txid_offset:2*txid_offset+2] txid_match=bytearray([parts[1]%256, int((parts[1]%65536)/256)]) return txid_part==txid_match # exact binary comparison # Unpacking and packing bitcoin blocks and transactions def OP_RETURN_unpack_block(binary): buffer=OP_RETURN_buffer(binary) block={} block['version']=buffer.shift_unpack(4, '<L') block['hashPrevBlock']=OP_RETURN_bin_to_hex(buffer.shift(32)[::-1]) block['hashMerkleRoot']=OP_RETURN_bin_to_hex(buffer.shift(32)[::-1]) block['time']=buffer.shift_unpack(4, '<L') block['bits']=buffer.shift_unpack(4, '<L') block['nonce']=buffer.shift_unpack(4, '<L') block['tx_count']=buffer.shift_varint() block['txs']={} old_ptr=buffer.used() while buffer.remaining(): transaction=OP_RETURN_unpack_txn_buffer(buffer) new_ptr=buffer.used() size=new_ptr-old_ptr raw_txn_binary=binary[old_ptr:old_ptr+size] txid=OP_RETURN_bin_to_hex(hashlib.sha256(hashlib.sha256(raw_txn_binary).digest()).digest()[::-1]) old_ptr=new_ptr transaction['size']=size block['txs'][txid]=transaction return block def OP_RETURN_unpack_txn(binary): return OP_RETURN_unpack_txn_buffer(OP_RETURN_buffer(binary)) def OP_RETURN_unpack_txn_buffer(buffer): # see: https://en.bitcoin.it/wiki/Transactions txn={ 'vin': [], 'vout': [], } txn['version']=buffer.shift_unpack(4, '<L') # small-endian 32-bits inputs=buffer.shift_varint() if inputs>100000: # sanity check return None for _ in range(inputs): input={} input['txid']=OP_RETURN_bin_to_hex(buffer.shift(32)[::-1]) input['vout']=buffer.shift_unpack(4, '<L') length=buffer.shift_varint() input['scriptSig']=OP_RETURN_bin_to_hex(buffer.shift(length)) input['sequence']=buffer.shift_unpack(4, '<L') txn['vin'].append(input) outputs=buffer.shift_varint() if outputs>100000: # sanity check return None for _ in range(outputs): output={} output['value']=float(buffer.shift_uint64())/100000000 length=buffer.shift_varint() output['scriptPubKey']=OP_RETURN_bin_to_hex(buffer.shift(length)) txn['vout'].append(output) txn['locktime']=buffer.shift_unpack(4, '<L') return txn def OP_RETURN_find_spent_txid(txns, spent_txid, spent_vout): for txid, txn_unpacked in txns.items(): for input in txn_unpacked['vin']: if (input['txid']==spent_txid) and (input['vout']==spent_vout): return txid return None def OP_RETURN_find_txn_data(txn_unpacked): for index, output in enumerate(txn_unpacked['vout']): op_return=OP_RETURN_get_script_data(OP_RETURN_hex_to_bin(output['scriptPubKey'])) if op_return: return { 'index': index, 'op_return': op_return, } return None def OP_RETURN_get_script_data(scriptPubKeyBinary): op_return=None if scriptPubKeyBinary[0:1]==b'\x6a': first_ord=ord(scriptPubKeyBinary[1:2]) if first_ord<=75: op_return=scriptPubKeyBinary[2:2+first_ord] elif first_ord==0x4c: op_return=scriptPubKeyBinary[3:3+ord(scriptPubKeyBinary[2:3])] elif first_ord==0x4d: op_return=scriptPubKeyBinary[4:4+ord(scriptPubKeyBinary[2:3])+256*ord(scriptPubKeyBinary[3:4])] return op_return def OP_RETURN_pack_txn(txn): binary=b'' binary+=struct.pack('<L', txn['version']) binary+=OP_RETURN_pack_varint(len(txn['vin'])) for input in txn['vin']: binary+=OP_RETURN_hex_to_bin(input['txid'])[::-1] binary+=struct.pack('<L', input['vout']) binary+=OP_RETURN_pack_varint(int(len(input['scriptSig'])/2)) # divide by 2 because it is currently in hex binary+=OP_RETURN_hex_to_bin(input['scriptSig']) binary+=struct.pack('<L', input['sequence']) binary+=OP_RETURN_pack_varint(len(txn['vout'])) for output in txn['vout']: binary+=OP_RETURN_pack_uint64(int(round(output['value']*100000000))) binary+=OP_RETURN_pack_varint(int(len(output['scriptPubKey'])/2)) # divide by 2 because it is currently in hex binary+=OP_RETURN_hex_to_bin(output['scriptPubKey']) binary+=struct.pack('<L', txn['locktime']) return binary def OP_RETURN_pack_varint(integer): if integer>0xFFFFFFFF: packed="\xFF"+OP_RETURN_pack_uint64(integer) elif integer>0xFFFF: packed="\xFE"+struct.pack('<L', integer) elif integer>0xFC: packed="\xFD"+struct.pack('<H', integer) else: packed=struct.pack('B', integer) return packed def OP_RETURN_pack_uint64(integer): upper=int(integer/4294967296) lower=integer-upper*4294967296 return struct.pack('<L', lower)+struct.pack('<L', upper) # Helper class for unpacking bitcoin binary data class OP_RETURN_buffer(): def __init__(self, data, ptr=0): self.data=data self.len=len(data) self.ptr=ptr def shift(self, chars): prefix=self.data[self.ptr:self.ptr+chars] self.ptr+=chars return prefix def shift_unpack(self, chars, format): unpack=struct.unpack(format, self.shift(chars)) return unpack[0] def shift_varint(self): value=self.shift_unpack(1, 'B') if value==0xFF: value=self.shift_uint64() elif value==0xFE: value=self.shift_unpack(4, '<L') elif value==0xFD: value=self.shift_unpack(2, '<H') return value def shift_uint64(self): return self.shift_unpack(4, '<L')+4294967296*self.shift_unpack(4, '<L') def used(self): return min(self.ptr, self.len) def remaining(self): return max(self.len-self.ptr, 0) # Converting binary <-> hexadecimal def OP_RETURN_hex_to_bin(hex): try: raw=binascii.a2b_hex(hex) except Exception: return None return raw def OP_RETURN_bin_to_hex(string): return binascii.b2a_hex(string).decode('utf-8')