Headaches for law enforcement

The digital currency has caused any number of headaches for law enforcement.

When the digital currency Bitcoin came to life in January 2009, it was noticed by almost no one apart from the handful of programmers who followed cryptography discussion groups. Its origins were shadowy: it had been conceived the previous year by a still-mysterious person or group known only by the alias Satoshi Nakamoto1. And its purpose seemed quixotic: Bitcoin was to be a 'cryptocurrency', in which strong encryption algorithms were exploited in a new way to secure transactions. Users' identities would be shielded by pseudonyms. Records would be completely decentralized. And no one would be in charge — not governments, not banks, not even Nakamoto. Yet the idea caught on. Today, there are some 14.6 million Bitcoin units in circulation. Called bitcoins with a lowercase 'b', they have a collective market value of around US$3.4 billion. Some of this growth is attributable to criminals taking advantage of the anonymity for drug trafficking and worse. But the system is also drawing interest from financial institutions such as JP Morgan Chase, which think it could streamline their internal payment processing and cut international transaction costs. It has inspired the creation of some 700 other cryptocurrencies. And on 15 September, Bitcoin officially came of age in academia with the launch of Ledger, the first journal dedicated to cryptocurrency research. What fascinates academics and entrepreneurs alike is the innovation at Bitcoin's core. Known as the block chain, it serves as the official online ledger of every Bitcoin transaction, dating back to the beginning. It is also the data structure that allows those records to be updated with minimal risk of hacking or tampering — even though the block chain is copied across the entire network of computers running Bitcoin software, and the owners of those computers do not necessarily know or trust one another. Many people see this block-chain architecture as the template for a host of other applications, including self-enforcing contracts and secure systems for online voting and crowdfunding. This is the goal of Ethereum, a block-chain-based system launched in July by the non-profit Ethereum Foundation, based in Baar, Switzerland. And it is the research agenda of the Initiative for CryptoCurrencies and Contracts (IC3), an academic consortium also launched in July, and led by Cornell University in Ithaca, New York. DigiCash went bankrupt in 1998 — partly because it had a centralized organization akin to a traditional bank, yet never managed to fit in with the financial industry and its regulations. But aspects of its philosophy re-emerged ten years later in Nakamoto's design for Bitcoin. That design also incorporated crowdsourcing and peer-to-peer networking — both of which help to avoid centralized control. Anyone is welcome to participate: it is just a matter of going online and running the open-source Bitcoin software. Users' computers form a network in which each machine is home to one constantly updated copy of the block chain. Nakamoto's central challenge with this wide-open system was the need to make sure that no one could find a way to rewrite the ledger and spend the same bitcoins twice — in effect, stealing bitcoins. His solution was to turn the addition of new transactions to the ledger into a competition: an activity that has come to be known as mining ('The Bitcoin game').

Mining starts with incoming Bitcoin transactions, which are continuously broadcast to every computer on the network. These are collected by 'miners' — the groups or individuals who choose to participate — who start competing for the right to bundle transactions into a new block. The winner is the first to broadcast a 'proof of work' — a solution showing that he or she has solved an otherwise meaningless mathematical puzzle that involves encrypted data from the previous block, and lots of computerized trial and error. The winning block is broadcast through the Bitcoin network and added to the block chain, with the proof of work providing an all but unbreakable link. The block chain is currently almost 400,000 blocks long. 

 In principle, this competition keeps the block chain secure because the puzzle is too hard for any one miner to solve every time. This means that no one will ever gain access to the encrypted links in the block chain and the ability to rewrite the ledger. 

 Source : www.nature.com