Key takeaways

Bitcoin’s blockchain allows users to embed hidden messages, functioning as both a financial ledger and a permanent message board.

Bitcoin’s OP_RETURN field enables users to store short messages without interfering with transaction data.

ASCII (American Standard Code for Information Interchange) is a basic text encoding system that converts characters into numerical values.

Embedding messages in Bitcoin’s blockchain reflects cypherpunk values of privacy, decentralization and resistance to censorship.

Bitcoin’s blockchain isn’t just a decentralized ledger; its technology also allows it to contain hidden messages.

ASCII (American Standard Code for Information Interchange), a basic text encoding system, allows users to embed short messages in the blockchain. These messages range from historical comments to pop culture references, giving the blockchain a dual purpose: a financial ledger and a message board.

This article explains ASCII messaging within Bitcoin and how ASCII text keeps the legacy of cryptography pioneers alive.

Why Bitcoin’s blockchain contains hidden ASCII messages

One of the most famous hidden messages is from Bitcoin’s creator, Satoshi Nakamoto, who embedded in the genesis block: “The Times 03/Jan/2009 Chancellor on brink of second bailout for banks.” This wasn’t just a timestamp — it was a direct commentary on the financial instability that led to Bitcoin’s creation, subtly hinting at Bitcoin’s purpose as an alternative to centralized banking.

Since then, many have followed suit. In 2013, someone embedded a full Rick Astley “Never Gonna Give You Up” song, essentially rick-rolling the blockchain. This was a playful use of the technology, but it underscores the freedom users have to express themselves through Bitcoin. Other messages include everything from wedding proposals to political statements about censorship and governance. Some have even embedded Bible verses or historical quotes, marking moments in time.

But why do people do this? It’s about more than just having fun. The blockchain is decentralized and immutable, meaning no one can erase or alter what’s written there. By embedding messages, people leave a permanent digital footprint, a lasting record that can’t be censored, modified or lost over time. It’s a way to express ideas in a place where no one entity has control — a form of free speech in its purest, most permanent form.

Did you know? The full lyrics of “Never Gonna Give You Up” by Rick Astley couldn’t be embedded in a single transaction. Instead, the person who rick-rolled the blockchain had to break the lyrics into chunks and distribute them across multiple transactions. This means the song’s lines are scattered across the blockchain, each piece encoded separately, creating a “fragmented” rick-roll that only truly reveals itself when pieced together by someone exploring those specific transactions.

How Bitcoin’s blockchain stores hidden messages

Bitcoin’s blockchain stores hidden messages by embedding ASCII text directly into transactions. This process is done using a field called “OP_RETURN.” It’s a part of Bitcoin’s scripting language that allows users to insert a small amount of data — like a message — without interfering with the transaction itself.

Here’s how it works:

Each Bitcoin transaction contains inputs (where the funds are coming from) and outputs (where they’re going).

The OP_RETURN field is part of the output, used to add up to 80 bytes of data to a transaction. This isn’t a lot of space — just enough for short messages, URLs or even hashes of larger files.

When the transaction is processed by the network, this extra data in the OP_RETURN is imprinted on the blockchain forever.

Because Bitcoin’s blockchain is immutable — meaning once data is written, it can’t be changed — the messages become permanent. This immutability ensures that whatever is embedded in the blockchain stays there for as long as the blockchain exists. Messages aren’t just stored for the sender or receiver; they’re accessible to anyone who wants to search the blockchain and see them.

So, how does this work without affecting Bitcoin’s functionality? Miners, who verify transactions and add them to the blockchain, process these transactions just like any other. The key thing is that the extra data (the hidden messages) doesn’t interfere with the core function of sending and receiving Bitcoin. It’s stored as metadata, separate from the actual transaction details like amounts and addresses. This ensures that Bitcoin’s blockchain remains efficient, even with these messages hidden inside it.

Indeed, the inclusion of OP_RETURN in a transaction is optional, and it doesn’t impact the validity of the transaction. Miners still verify the transaction based on its inputs and outputs, ensuring that the blockchain continues to function properly, even with a growing collection of hidden messages. Essentially, the messages are like tiny footnotes in the ledger, added for posterity but not affecting the flow of Bitcoin’s network.

Did you know? The OP_RETURN field isn’t just used for embedding messages; it also plays a role in other creative uses of Bitcoin’s blockchain, like ordinals.

The role of ASCII text in Bitcoin’s hidden messages

ASCII is a basic encoding system that converts characters into numerical values. Each letter, number or symbol is represented by a unique number between 0 and 127, making it a straightforward way to store text as digital data. For example, the letter “A” is represented by the number 65 in ASCII, while the space character is represented by 32.

In Bitcoin’s blockchain, this encoding works by converting the desired text into a sequence of numbers. These numbers are then recorded in the blockchain’s OP_RETURN field as hexadecimal data. To visualize how ASCII works, let’s take the word “Hello.” In ASCII, this is encoded as:

H = 72
e = 101
l = 108
l = 108
o = 111

This sequence — 72, 101, 108, 108, 111 — gets converted to hexadecimal format as 48656c6c6f, which can then be embedded in a Bitcoin transaction. When viewing the blockchain, specialized software or even manual conversion can decode the hexadecimal data back into human-readable text.

The OP_RETURN field in Bitcoin transactions allows for up to 80 bytes of data. Since each ASCII character takes up 1 byte, that leaves room for around 80 characters in a single transaction. This is where the technical limitations come in: Messages have to be brief, meaning users often have to be creative with their wording or choose short, impactful phrases.

For example, let’s look at a tribute embedded in Bitcoin’s blockchain after the passing of Nelson Mandela in 2013. The message read: “Nelson Mandela - May your soul rest in peace. We will always remember you!” Each character in this text corresponds to a specific ASCII number. This sequence was then converted to hexadecimal and embedded into block 277,316, ensuring the tribute remains a permanent part of Bitcoin’s digital ledger. Like other messages, this one is now an unchangeable record of a historical moment, forever preserved on the blockchain.

While the simplicity of ASCII makes it ideal for encoding human-readable messages, there are some trade-offs. ASCII is limited to basic text and symbols, so anything more complex, like images or detailed instructions, requires other formats or methods. Additionally, the small size of the OP_RETURN field limits the scope of the message. Yet despite these limitations, ASCII remains a powerful tool for embedding meaningful content on the blockchain, especially when users aim for simplicity, universality and permanence.

Did you know? The first use of ASCII dates back to 1963. It was developed by a committee of the American National Standards Institute (ANSI) to standardize the way text and symbols are represented in computers and electronic devices.

A nod to cypherpunk tradition

Early cryptographers, known as cypherpunks, envisioned a future where cryptography would protect personal privacy and decentralize power away from centralized institutions. Their influence is evident in Bitcoin’s use of cryptographic proof and the blockchain’s role as a decentralized, immutable ledger.

Hal Finney, who was one of the first people to receive a Bitcoin transaction from Satoshi Nakamoto, was a renowned cryptographer and cypherpunk. Finney developed Reusable Proofs of Work (RPOW), a precursor to Bitcoin’s proof-of-work mechanism, and was deeply interested in cryptography’s potential to secure privacy.

Adam Back, the creator of Hashcash — another foundational concept behind Bitcoin’s mining algorithm — was also a key figure in the early cypherpunk movement.

This tradition extends to notable figures like Len Sassaman, a cypherpunk who worked on PGP and was an advocate for privacy and anonymity. In 2011, an ASCII tribute to Sassaman was embedded in the Bitcoin blockchain after his passing, a lasting mark on the decentralized ledger.

These individuals, along with others, shared a vision for how decentralized, cryptographically secure systems could reshape financial and social structures.

Did you know? In the early 1990s, the cypherpunks predicted many of today’s privacy concerns, such as mass surveillance and data breaches, and they actively worked on solutions to counter these issues. Their mailing list, which started in 1992, became a breeding ground for revolutionary ideas, including the creation of cryptographic protocols like digital cash (a precursor to Bitcoin), anonymous communication systems and encryption tools like PGP (Pretty Good Privacy).

Their values — privacy, decentralization and resistance to censorship — are closely tied to Bitcoin’s blockchain and its use for hidden messages. Indeed, when users embed ASCII messages into the Bitcoin blockchain, they’re engaging in a practice that mirrors the philosophy of these cryptography pioneers.

Whether it’s a tribute, a political statement or even a joke, the act of leaving a permanent mark on a decentralized ledger reflects the cypherpunk values of individual autonomy and expression.

Disclaimer：

1. This article is reprinted from [cointelegraph], All copyrights belong to the original author [Bradley Peak]. If there are objections to this reprint, please contact the Gate Learn team, and they will handle it promptly.
2. Liability Disclaimer: The views and opinions expressed in this article are solely those of the author and do not constitute any investment advice.
3. Translations of the article into other languages are done by the Gate Learn team. Unless mentioned, copying, distributing, or plagiarizing the translated articles is prohibited.