When cryptocurrencies hit the mainstream in the 2010s, the technology was widely viewed as a perfect vehicle for crime. A drug dealer or scam artist could transfer large quantities of money instantly, without relying on a bank to validate the transaction. To early advocates, crypto was appealing because it promised the secrecy and anonymity of cash, without the inconvenience of face-to-face exchanges.
That secrecy was an illusion. Crypto transactions are inscribed on a publicly viewable ledger called a blockchain. To the untrained observer, blockchain records are unintelligible — a jumble of meaningless letters and numbers. But a growing industry is dedicated to deciphering them.
Source: The Crypto Detectives Are Cleaning Up – The New York Times