The previous seven chapters have been designed to give you a solid grounding in how cryptocurrencies work. You should now understand the concepts of a distributed ledger, the fundamental math that underpins the blockchain, the way public and private keys interact, and how transactions actually function. We have also looked at both software and hardware wallets, and considered their individual merits as well as the application of blockchain technology to contracts and ICOs.

You can now apply this knowledge to the techniques and tools that you can use to investigate crimes that use cryptocurrencies. For example, purchasing illegal goods or storing illegally acquired funds, or alternatively crimes committed against users of cryptocurrencies, stealing online funds through fishing, fraud, and so on.

In this section, we will look at a wide range of techniques to identify where a suspect is using cryptocurrencies, acquiring addresses and private keys, following the money, visualizing transactions using free tools, and attempting to link an address to a particular user.

It is worth noting that a number of excellent software tools for investigating cryptocurrencies are available to purchase that will help considerably in following the money and identification of a user. Chainalysis (https://www.chainalysis.com/) and Elliptic (https://www.elliptic.co/) are both excellent tools, and I urge you to buy one of them, but please remember that both of these tools are for investigating Bitcoin only (at the time of writing), and they cost a significant amount of money! The techniques I will teach you in the coming chapters will focus on Bitcoin and Ethereum, but the concepts will work with any cryptocurrency. So it is vital that you do not just learn to use one tool and are then stuck when you are faced with investigating other currencies. Techniques used by both tools attempt to almost brute-force an eventual identification of the owner of a particular address. Although I will cover how to do these things manually, they are very difficult and time-consuming if attempted outside of these specialist tools.