Researchers from Germany found in the Bitcoin blockchain prohibited content

Researchers from Rhine-Westphalian technical University of Aachen in Germany found the illegal content in the Bitcoin blockchain that could potentially make it illegal in many countries — at least give authorities a good reason for this.

German researchers say that some users consider the blockchain as nadezhnoe place to store images and links to abuse of children and other prohibited materials.

The blockchain is a distributed registry that you create with the software open-source software, which records every bitcoin transaction. N in each transaction can be stored and a small amount of non-financial data — from texts to links and files.

On pages 2-5 of the research methods of content placement in transactions. This can be used by the input script (P2SH-injection), but mostly weekend — methods OP_RETURN and coinbase field (available only to miners), as well as the initial transaction to transfer bitcoins — for example, when generating keys and hashes in a given sample (arbitrary text string, including proper links to prohibited content). And the use of built-in scripting language opens up even more possibilities to embed arbitrary content. According to the calculations of researchers, the standard block size of 1 MB can be placed up to 60 KB third-party data. Of course, it’s not free — it will have to pay a Commission to the miners, which during the filling of the whole unit can be tens of thousands of dollars.

There you also have the services that offer space in the blockchain random data. Among them are listed CryptoGraffiti, Apertus and Satoshi Uploader.

The researchers found in the blockchain of Bitcoin is approximately 1 600 files, some of them with questionable content. At least eight of them pornographic materials, one of which is associated with the abuse of children. Two more files contain 274 links to similar content, 142 of which lead to the darknet.

«Our analysis shows that some content, such as prohibited pornography, can make the blockchain illegal,» write the researchers.

«Although the specific judicial decisions does not yet exist, documents of law-making in countries such as Germany, UK or the USA, suggest that the restricted content can do keep a copy of the blockchain illegal for all users. In particular, it will jeopardize a multibillion-dollar industry of cryptocurrency».

While bitcoin use is not required to hold a copy of the blockchain on the device user, some processes, such as mining, require the download of the full blockchain or its parts.

«Because all the data in the blockchain is downloaded and permanently stored by users, they are responsible for any unwanted content added to the chain. Therefore, if the blockchain contains prohibited materials, to keep it illegal,» the researchers said.

Since mining is required for Bitcoin work, the presence of inappropriate content according to researchers can lead to serious problems for cryptocurrencies.

This is not the first warning about the dangers that bears storing non-financial data in the blockchain. In 2015, Interpol sent
a warning which stated that «the architecture of the blockchain implies the existence of the possibility of introduction of malware and its distribution, and the lack of methods of disposal of such information.» The Agency warned that this technology can be used for «distributing materials of sexual violence against children, and the blockchain could become a safe haven for the storage of such data».


The data of German researchers is the first public confirmation that the illegal content posted in the Bitcoin blockchain. The potential to embed in the blockchain of any content known for many years, and informed users published links to the blockchain posted in wedding photos or contracts. For example, a company locates in Bitfury Bitcoin blockchain data from the land cadastre of Georgia.

However, still the problem of possible storage in the blockchain illegal content will not dwell, although specialized resources on it it was known five years ago. Not ruled out the possibility that this study was conducted in order to strengthen political pressure on the cryptocurrency. Individuals and organizations interested in such developments, more than enough.

However, this fact can be a lot of mixed aspects, including from a legal point of view.

First, any information is stored in the blockchain not in the clear and decrypting and receiving need to know where to look and how to. If the read transaction from the blockchain plain text serious problems not, you to download multimedia content, including pictures, requires a precise statement about the location and how to decode the data.

Second, the placement of content in the blockchain close to widely known methods of computer steganography to hide, for example, pornographic images inside photos of cats or quite peaceful landscape. However, hardly anyone explores the billions of photos in social networks on the subject of the content of prohibited information.

And thirdly, perhaps most importantly — the prohibition of storage of the blockchain the Bitcoin law-abiding users will have little to contribute to their destruction, so as to control the blockchain at a modern level of development of the Internet is practically impossible. To store such information in any blockchain, including and is not intended for financial transactions. Thus, the implementation of such a ban is equivalent to a complete ban on all public block chain and puts into question the use even of corporate blockchains, which prohibited information may be, for example, downloaded by hackers.

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