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There’s neither official statement nor rumours on forums, but anyone observing any Bitcoin address on Blockchain.info block explorer will notice the taint analysis menu missing from the top menu bar. For years one of the few services employed by bitcoin forensics and intelligence investigators, the taint analysis function provided insights on direct and indirect links between Bitcoin addresses, giving the chance to check the reliability of mixing/tumbling services, money laundering websites and the anonimity of transactions.

Just to give an example, that’s what the Silk Road Seized coins Blockchain.info portrayed on on december of the past year, the highlighted red rectangle shows the Taint Analysis function available among the Tools:

The same page today is pretty different, in that the “Taint Analysis” function is clearly missing form the “Tools” section:

The Taint Analysis function was never that clear, there was more talking and information on forums such as BitcoinTalk or on reddit than on the blockchain.info website itself stesso. We tried to get in touch with the developers to ask for some insights on the taint analysis service but with no success, so developers of other bitcoin forensics and intelligence tools implemented taint analysis in different and interesting ways.

That’s how Blockchain.info define(d) taint analysis of incoming transactions “Received (Origin) Taint” o simply “Taint Analysis”:

Taint Analysis

Taint is the % of funds received by an address that can be traced back to another address.

This pages shows the addresses which have sent bitcoins to 1F1tAaz5x1HUXrCNLbtMDqcw6o5GNn4xqX. The data can be used to evaluate the anonymity provided by a mixing service. For example Send Coins from Address A to a Mixing service then withdraw to address B. If you can find Address A on the taint list of Address B then the mixing service has not sufficiently severed the link between your addresses. The more “taint” the stronger the link that remains.

Outgoing transactions taint analysis, marked as “Sent (Reversed) Taint” o “Forward Taint Analysis”, are (were) described as follows on the Blockchain.info website:

Forward Taint Analysis

Reversed Taint is the % of funds sent from an address which passed through another address.

This page shows the addresses which have received bitcoins from 1F1tAaz5x1HUXrCNLbtMDqcw6o5GNn4xqX. The greater the taint the stronger the link between the addresses.

Actually, though the Taint Analysis link is missing from the Blockchain.info menu, there’s still a way to access the function via direct URL call, typing the Bitcoin address the user is interested in analysing after the address “https://blockchain.info/taint/“. We can therefore access the Taint Analysis of the aforementioned address by typing the following URL on the address bar of our web browser: https://blockchain.info/taint/1F1tAaz5x1HUXrCNLbtMDqcw6o5GNn4xqX.

The displayed page contains the taint analysis but it sounds incomplete, often not updated… just check the incoming transactions taint analysis of the Silk Road Seized Coins which received hundreds of incoming transactions but on the taint analysis report contains only a handful of addresses. We tried with other addresses and the result is the same, many addresses are missing from the direct and reverse taint analysis on the Blockchain.info website.

Let’s wait and see if that’s a temporary malfunction or a planned free service removal, maybe to enhance it and offer it as a paid service, who knows…