The network that records Bitcoin payments has been found to store files and links to child abuse images which are impossible to remove, researchers have discovered.

Buried within the Bitcoin blockchain are more than 1,600 files and images, including hidden links to child pornography, according to researchers from the University of Aachen in Germany.

While most of these files were mundane, several files contained a total of 274 links to dark web sites or files containing illegal child sex abuse images. There was also one image within the blockchain itself showing a minor.

Bitcoin’s blockchain can be downloaded, coming to more than 100GB in total, although this is not needed for making payments.

The blockchain is supposed to be a digital record of all transactions used by cryptocurrencies, but the existence of illegal material on it means any user who downloads it could be at risk of prosecution under child protection laws.

“Our analysis shows that certain content, e.g., illegal pornography, can render the mere possession of a blockchain illegal,” the researchers said. “Among these files there is clearly objectionable content such as links to child pornography, which is distributed to all Bitcoin participants.”

Bitcoin’s blockchain is the distributed ledger which is used to confirm payments and transfers of Bitcoin. It works by having users verify transactions, meaning no one person is in control of it. But files can also be sent embedded into the blockchain.

The system is designed to be irreversible and can leave information stored on the blockchain indefinitely, a feature which the researchers say “put all users at risk when objectionable content is irrevocably stored on the blockchain”. It could even make storing Bitcoin’s blockchain illegal in the UK, US and other countries.

These files were very hard to find, so a normal user who downloads the Bitcoin blockchain is unlikely to stumble upon them. Only around 1.4 per cent of Bitcoin transactions included non-financial data, but the researchers suggest future blockchain technology needs to find a way to protect users from unintended data, or illegal content, that might be inserted or stored within the ledger.

Our source: https://www.telegraph.co.uk/technology/2018/03/20/bitcoin-blockchain-includes-hidden-child-abuse-files/