- a Proof of Existence and a message board for the Cardano blockchain

Hello, everyone!

Link first:

Now the story and explanation:
The first phase of Goguen added the possibility to add metadata to a regular transaction. Probably, I was glad about this event even more than Charles himself was. The thing is that four years ago, I wanted to implement a project that would allow anyone to post a word (or better – many words) into Bitcoin’s blockchain. That was technically possible, but I’ve abandoned the idea since I have studied the feasibility of OP_RETURN, and it turned out that it had been possible to post there only 80 bytes. Back then, it was only 40 bytes, which is even worse. One could only boast with such a message only to geek friends who could convert the hexadecimal string into text. So my wife would not understand such a message! :thinking:

Cardano has added an excellent opportunity to put into transactions beautiful and structured data of up to 16 Kb in volume. You can view this data in blockchain explorers, such as AdaStat, Cardanoscan, or Cardano Explorer. There are new opportunities to save data permanently, which one might need someday. One of them is the Proof of Existence. I’ll explain it for those who don’t have a clue what this is:

Every file has a unique hash sum that’s calculated based on an algorithm (I’ve decided to use SHA256 and the size of the file in Bytes). Nobody can create a file with different content but with the same hash sum and size. The blockchain network plays the role of a cryptography notary here. If you send a hash sum of your file to the blockchain, you create proof that your file has been existing in an exact moment. You do not send a file itself into the blockchain – you only send the hash sum. You do not disclose your file’s contents to anyone since it is impossible to recreate a file from its hash sum. But the fact that it is impossible to delete or alter information containing in the blockchain allows everyone to use the Proof of Existence to protect digital property. If you have created something with your authorship’s copyright, like a book or a musical track, you can send a hash sum to the blockchain to create the Proof of Existence. If you add some additional information, such as your digital signature or author data, you can claim your copyright in the future.

I have loads of ideas about improvements that I plan to implement in CardanoWall. Right now, I have managed to create a workable product, which allows sending a message with any text therein and, in the case of necessity, merely selecting a file from your computer to create the PoE.

Your browser will calculate the hash sums of files and fulfill the required fields. It is important to understand that the entire process occurs only in your browser, so you don’t send your files to any server. Sending each transaction into the blockchain isn’t free of charge, so I cannot make such a service run on a free basis. A text message has its limitations for line length in Bytes. CardanoWall will automatically adjust the text to the required format, so you don’t have to worry about anything. The preview under the text gives a full understanding of how it will look like once posted. Also, I’ve created it with anonymity in mind, so there is no registration on the website. An email that you enter to the payment field is only needed to send you a unique code with the balance for sending messages.

Since the email is not saved anywhere on my website, try not to lose your balance code since I cannot restore it. You can send any text, so I’m asking you to act eco-friendly. Do not send to blockchain any data that might insult or hurt someone, including the future you. I created this project to bring added value and use the Cardano network’s amazing features, in the bright future of which I genuinely believe. Besides, that was my dream for a long time to send ‘Hello’ to my mom and friends with a blockchain message. So… Hi, dear! Cardano Blockchain is cool! :bouquet: (

PS: I also run my stake pool called [VICE]. I direct its profit to the development and support of the CardanoWall service and the development of my other projects / new ideas I am currently working on to bring more adoption to Cardano. Join my pool and support the decentralization by delegating to private pools!


I switched the hashing algorithm from SHA-256 to SHA3-256. Hash calculation in the browser takes more time, but it has higher resistance to attacks.