Bitcoin's dirty secret: Disgusting images found on the blockchain?

in #bitcoin3 years ago


In the past few days, various news sites have been claiming that there is child pornography on the Bitcoin blockchain. In true modern journalistic style, many of the articles reporting on it failed to include the link to the study. Many of the headlines read that child pornography was found on the blockchain, but later in the article made the softer claim of links to such websites, such as in this article

"Then there were the clearly harmful files. Of the total, 59 files had links to images of child exploitation"

Arrested for a URL

Despite my best efforts, I couldn't find any cases where anyone had been arrested for possession of a web address in general, let alone for the ones on the blockchain, even though this problem has been known publicly since 2013, and it wouldn't be hard for law enforcement to trace the IP of a Bitcoin node.

However, an arrest might be possible as many jurisdictions have statutes regarding the dissemination or communication of such material.

Technically impossible?

One article by Kai Sedgwick of claims that it's technically impossible to store images on the Bitcoin blockchain, as you can only store 80 or 100 bytes of data in a transaction - enough for a sentence of text, but not enough for an image.

bitcoin whitepaper transaction.png

In the comments, someone mentioned that there's more to it. You can store larger amounts of information on the blockchain, using transactions with multiple outputs. Every output contains a small amount of data, and if you have the know-how to put the puzzle pieces together, you can assemble the document stored there. One such transaction contains the Bitcoin whitepaper.

A paper from Augustuna College, Data Insertion in Bitcoin's Blockchain lays out various methods of storing data on the Bitcoin blockchain, and gives examples from the wild, including this picture of Nelson Mandela:

data insertion - nelson mandela.png

The image in question

So it's technically possible to store images, and it has been done. Some of these articles are claiming that there are only links, and some are claiming that there is one illegal image in the Bitcoin blockchain. This is the paper they're citing - A Quantitative Analysis of the Impact of Arbitrary Blockchain Content on Bitcoin

Matzutt and his colleagues write:

Bitcoin’s blockchain contains at least eight files with sexual content. While five files only show, describe, or link to mildly pornographic content, we consider the remaining three instances objectionable for almost all jurisdictions: Two of them are backups of link lists to child pornography, containing 274 links to websites, 142 of which refer to Tor hidden services. The remaining instance is an image depicting mild nudity of a young woman. In an online forum this image is claimed to show child pornography, albeit this claim cannot be verified (due to ethical concerns we refrain from providing a citation).

In case you're unaware, Tor is a browser used for accessing the Dark Net where a lot of illegal activity occurs. Tor addresses are frequently changed, and so it's likely that the addresses contained in the blockchain are no longer current.

So the real story is, there are many, likely outdated and useless, Dark Net links on the Bitcoin blockchain, and one image of a mildly nude young woman of indeterminate age. Of course, it's possible that someone will put up illicit images at any moment.

Possible solutions

Active filtering

I've already seen some control freaks saying that every piece of data should be screened before it enters the blockchain. To most Bitcoiners, that conjures an image of a government coin agent, putting a big red "REJECT" or "ILLEGAL" stamp onto applications to pay their water bill, turning the new medium into a bureaucratic organisation akin to the DMV.

The idea of attempting to control data entering the system goes against the idea of "innovation without permission", and for that reason it's unlikely to be accepted - firstly, because it goes against the freedom allowed by the Bitcoin infrastructure, and secondly, if it ever were implemented, people would just innovate a new system to avoid it.

Pruning the blockchain

There's a common misconception that, if you have the Bitcoin blockchain, you have to have the entire thing. In fact, many nodes remove unnecessary data, which is known as "pruning". If illicit images becomes a serious problem on the blockchain, miners and other nodes can maintain an off-chain record of which data to delete.

You don't have to have the blockchain at all in order to use Bitcoin, but many enthusiasts like to have it. For those few, it might be impractical to prune the offensive data, compared to mining operations which can design systems for it.

Bitcoin developer Gregory Maxwell proposed a solution to ensure that excess data would be prunable, though it was never implemented.

A guilty mind and a guilty act

Once upon a time, there was a concept in law called "mens rea" or "guilty intent". You had to have the intent to do something bad to be convicted of a crime - the act alone isn't sufficient. Clearly, most people who download an entire, intact copy of the Bitcoin blockchain, all 149 gigabytes of it, aren't doing it so they can get a single image of a mildly nude woman, or some Dark Net links. They're doing it because they want to facilitate and confirm transactions.

Of course, that doesn't mean that people won't be prosecuted for holding the Bitcoin blockchain. There are many cases of governments finding excuses to arrest people they find politically inconvenient, and technology like blockchain is indeed inconvenient.

For example, In 1994, Nixon's assistant for domestic affairs John Daniel Ehrlichman said, "The Nixon campaign in 1968, and the Nixon White House after that, had two enemies: the antiwar left and black people. You understand what I’m saying? We knew we couldn’t make it illegal to be either against the war or black, but by getting the public to associate the hippies with marijuana and blacks with heroin, and then criminalizing both heavily, we could disrupt those communities. We could arrest their leaders, raid their homes, break up their meetings, and vilify them night after night on the evening news. Did we know we were lying about the drugs? Of course we did."


John Daniel Ehrlichman

The point is, if you want to attack a class of people, it's a lot easier to go after something tangential which is easily demonised. It's hard to ban Bitcoin directly, but it's easy to get people angry about child abuse.

In this case, I expect that authorities won't get involved, as that is the natural continuation of their past and present behaviours.

Conclusion - the most likely solution

When you look at a man or a woman, at a friend at his death for example, there are many ways to assess his life. Maybe you would think about the time he never paid you back the money he owed you, or judge him for the times he shoplifted as a youth. More likely, you'd think about the fond memories you shared together, the simple moments of pleasure, and the positive effect he had on those around him.

A blockchain is similar, a record of many mutually beneficial transactions, many of which would not have been possible before this technology existed - allowing Venezuelan smugglers and African nomads to feed their families, and even move into prosperity. It might be a rush to judgement, to call for people to "delete all your blockchain records", as some authors have done.

The solution that is most likely with Bitcoin is a simple one, and some won't like it, though in time they will also participate. The solution is: Just ignore it, and then forget it. The blockchain offers little likelihood of justice for anyone who might have been abused, but nor does it offer further abuse. If you never take the time to decode the images or links, if you forget about them, they may as well not be there.

For most Bitcoiners, this news story will appear as short-term noise, just as it eventually became the first time it was mentioned. It will likely have no lasting effect on price or use of the currency, and soon enough the alarmists will shout about other things.

Image attribution: Bitcoin Crying girl

CYN-001_TWITTER smaller.png

Kurt Robinson for Cryptonomics - Principles of cryptocurrency and investing


There is no way to actively filter the bitcoin blockchain.
Not without seriously destroying its usefulness.

A picture can be stored as a poem. Are you going to ban all words?

Anyway, the most likely way for you to get kiddy porn is to go to a honey pot website, and it will download a bunch of things into your cache folder, that you never even knew was there. A kiddy porn picture could be this period. And you would never know it.

The feds will do any dirty thing to bust you. Having everything squeaky clean just makes it a little harder for them. "He had a gun"

So, the best way is to ignore it.
And keep spreading bitcoin. Because the faster bitcoin spreads, the faster the FED will be dead. And they won't have any money to send thugs with guns to your house.

this is a lot of non-sense, trying to tie and tangle BTC with something like this. its like associating any and every terrible thing that money has paid for with a certain currency etc.

rmartin should be arrested for inciting treason against the country America.. He's the type of person to say something like "Can I now be arrested for connecting to the internet since I can now hypothetically find links to or images of child rape?"

Yea you are right ..
Please check out my post @mr-awesome

My latest post on

Exactly right. They love those honey pots. They say by the end of the Silk Road, most of the sellers on there were feds.

Ah Kurt, the ever soothing voice of reason in any sea of FUD :)

On some other pages, such as the article, people are still claiming that it's impossible to store arbitrary data such as images. A cool way to demonstrate that it's not true is to look at the genesis block on an explorer.

Behold: Bitcoin Genesis block on

You can clearly see the text:

The Times 03/Jan/2009 Chancellor on brink of second bailout for banks

It's not the fault of blockchain or bitcoin on how it it used. Just like you can't blame the US Dollar for funding more terrorism, wars and drugs. Blame lies on the user or abuser.

Lets assume its true and images can be stored on the Blockchain so what? Images can be stored on computers and servers etc, nothing new. Trying to label the blockchain "bad" because it can or maybe used in criminal activities, to me is a lame argument. Every legal human activity has been exploited by criminals. Should we now stop living because of that? This sounds like a case of giving a dog a bad name so justify killing it.

Yes. Obviously hack journalists are going to portray this as something bad about the technology in general. It is slightly different to having a server which has the potential to store an image, because in this case, there is a real image on the blockchain of questionable legality.

No doubt but what do they suggest be done?

it is difficult for bitcoin to be maintained and in these period where the cryptomoneda are receiving persecutions by governments, tax payment, binace, security, banks.
Every day a new cryptomoneda is born, investors come and go. other currencies that are growing and investors change for the bitcoin to rise to 15000 before July has to see balance and stop the chase and the morbid bitcoin

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That’s so sad