02 Nov Symbol Blog and the Perplexing PNG puzzle

THIS EXAMPLE IS NO LONGER WORKING – PLEASE SCROLL TO THE BOTTOM OF THE ARTICLE FOR AN UPDATED EXAMPLE

Gimre posted this tweet a while back now and I wanted to give it a go but kind of thought that someone else would solve it in no time and I would spend hours working on it and get nowhere. Anyway, I decided to have a go last night and failed miserably but I had no idea why. It turned out that it just required 5 minutes of reading on PNG file format and it was a super easy fix.

Can you assemble it?https://t.co/uVd1A4A0ZQhttps://t.co/aXR3rgQZ1h

— gimre^xymcity 🇺🇦 (@NCOSIGIMCITYNRE) October 27, 2021

In this hastily written article I am going to take you through my hastily written code, apologies it is messy and probably clunky and inefficient. I basically know zero Python syntax so it will look like a 10 year old wrote it. I am amazed that I managed to get it to work (even if the problem was simple!) 😁

import urllib.request
import json
from binascii import unhexlify
NODEURL = "http://symbolblog-testnet.com:3000"

Spoiler: this was the killer for me. I did all of the rest really quickly but there was one missing element that I needed to add.. The PNG header (89 50 4E 47 0D 0A 1A 0A) once I added this to the beginning of the file that I output the image magically appeared – it was a eureka moment for me. Nothing more satisfying than solving a problem 😁

unhexlify("89504E470D0A1A0A")
b'\x89PNG\r\n\x1a\n'

Next it was just a case of taking the first transaction http://symbolblog-testnet.com:3000/transactions/confirmed/5B1A42E157411311B5F0302E6A1F9150C0E21BFBBE4741662F9922279A44570B and following the trail.

There were two messages “0000000D49484452000005000000050008030000002F3A0FC5”:

b'\x00\x00\x00\rIHDR\x00\x00\x05\x00\x00\x00\x05\x00\x08\x03\x00\x00\x00/:\x0f\xc5'

This was part of the file that we would assemble. And the second longer message:

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

Contained information on the other aggregate transactions needed to assemble the file:

b'\x00\x00\x03+iTXtAggregates\x00\x00\x00\x00\x00hashes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xd1\x95\x17H'

So I just stuck all of the transactions into an array and sequentially pulled all messages from each transaction (I think that there were 306 of them?) and “unhexlified” the results.

#Loop through all messages in each of the transactions from txarray

for tx in txarray:
    url = NODEURL + '/transactions/confirmed/' + tx
    req = urllib.request.Request(url)
    with urllib.request.urlopen(req) as res:
        data = json.load(res)
        i=0
        for d in data['transaction']['transactions']:
            msg = unhexlify(data['transaction']['transactions'][i]['transaction']['message'])
            xs=xs+msg
            i=i+1

Then I just wrote everything to a binary file called image.png opened up the folder I saved it to and I saw a thumbnail of the png – problem solved 😁

Here is the image:

I have added all my code below. If you run this through you should get the same image file!

import urllib.request
import json
from binascii import unhexlify

NODEURL = "http://symbolblog-testnet.com:3000"

#Pesky PNG header
xs= unhexlify("89504E470D0A1A0A")

#Looks like this:
unhexlify("89504E470D0A1A0A")

f = open("output.png", "wb")

#First message in initial transaction
xs= xs+unhexlify("0000000D49484452000005000000050008030000002F3A0FC5")

#Looks like this:
unhexlify("0000000D49484452000005000000050008030000002F3A0FC5")

#Second message in initial transaction contains the other aggregate transactions
unhexlify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

#Array of transactions above..
txarray = ['6F40B5513D412373A3851D59DBB7BDF67BFB27C247CFF5AE64D987B7B8BC237C', '84C30671D2BA9FE1A969F772ADF3D8B4A3A5184CC3E1DA624E781E5F1687BCD1', '75BF87E8762BA13B8A48DFEEE11BB86A2411EFDECA4532C20BBAED1D109E842C', '9E5ACE4DA8725DE8F31FFB70E58B85CB5B9617048AA2423FCEEEF3CC39E72C55', '84B6D379B237CE7CA552133CEFDFBE26549EAC37261EFA9558BE696D06EBDB08', '22F67D9FB7A9E21C5DC169CAD49B6BEA41ED0AAF4DB36114C3A08F9698EA1552', 'A2A294B1511724D1EDAEA6974738F391E7887C4BFD3B1709210ADF57CA172217', '1B90C1778AD7C2086A13E21BE0FE89CDF2DDDC5D9583D6F2EDB1E40B4D0602A1', '3587976B3F869CACA66CF7943E88359CE08CB9E55D23AEC82F0920115D998252', 'C8F3F409389E6A2A98C771F122D18647CAAA25D427C27D10405DEB468A96899A', '97BAE639AD05AEE057607A0938B0BEB48811B9C7341F25CEE8037F7D9EAD0D10', '9432BC2771470A9CF97B2D40E96C5CF348AD167008BFCD4109CF95E7BA9FC002']

#Loop through all messages in each of the transactions from txarray

for tx in txarray:
    url = NODEURL + '/transactions/confirmed/' + tx
    req = urllib.request.Request(url)
    with urllib.request.urlopen(req) as res:
        data = json.load(res)
        i=0
        for d in data['transaction']['transactions']:
            msg = unhexlify(data['transaction']['transactions'][i]['transaction']['message'])
            xs=xs+msg
          #  print(msg)
            i=i+1

# Write data to the png file
f.write(xs)

Run it yourself

You can download my Jupyter Notebook file here and run the code yourself (hopefully it will work for you too!) 😁 You can even run it on Google Colab and see the output:

Update 04/10/22

The example above is no longer working as there was a testnet reset. However, I have included an update using an image stored on the Symbol mainnet. You can download the Jupyter Notebook here.

There’s also something special about this image – hint: look at the PLTE data 😊

pic.twitter.com/Rtk2IWp8MB

— Symbol Blog (@blog_symbol) January 20, 2022