It's been another formative year in the world of bitcoin and the blockchain, and while the price has been subdued over much of the year, other developments in the space have arguably been more intriguing than in any 12-month period previously.

We've seen companies come and go, record-setting funding rounds, increased interest in the technology and, sadly, occasional bad actors still stirring negativity into the mix.

In this year-end special, we look back at the news stories that made the most impact during 2015.

The year got off to a shocking start on 5th January when bitcoin exchange Bitstamp released a statement admitting that it had suffered a major hack and lost "less than 19,000 BTC", or about $5.1m at the time.

In a statement, Bitstamp said an undisclosed number of wallets had been compromised, and that upon learning of the breach, it had issued warnings to users and moved to suspend operations.

A report, supposedly leaked from the exchange, later suggested that six Bitstamp employees had been targeted over some weeks in a phishing attempt that led to the theft. Eventually, the hackers were able to access two servers containing the file for Bitstamp’s hot wallet and it passphrase.

Following the attack, the exchange put in place multi-sig wallet access and contracted bitcoin security firm Xapo to handle its cold wallet storage.

However, the incident still served to set the tone for what would be a bleak first half of the year for the industry as a whole, particularly for exchanges, which struggled to find revenues amid increased competition and lower-than-expected user adoption.

Later in January, wallet and exchange provider Coinbase announced that it had raised $75m as part of a Series C funding round – smashing the previous record for a bitcoin company.

Asides from the figures, the backers were equally impressive.

The round included a host of impressive first-time bitcoin investors including the New York Stock Exchange (NYSE), Fortune 500 financial services group USAA, Spanish megabank BBVA and Japanese telcom giant DoCoMo. Former Citigroup CEO Vikram Pandit and former Thomson Reuters CEO Tom Glocer also contributed personal investments.

Coinbase CEO Brian Armstrong suggested at the time that the funding would help shift the mainstream perception of bitcoin during what had so far been a rocky year for the industry.

Armstrong told CoinDesk:

While the fundamentals of the network would continue to be debated, Armstrong was on the money with his prediction about funding, with the round serving as the opening salvo for what would be a year marked by a substantial increase in interest from financial incumbents.

The Wall Street Journal published a scoop in March, revealing that stealth startup 21 Inc had raised $116m in funding, a figure that served to put Coinbase's $75m January round, at least temporarily, in the shade.

21 Inc's then-CEO Matthew Pauker indicated at the time that Andreessen Horowitz, Data Collective, Khosla Ventures, RRE Ventures and Yuan Capital were among the firms that invested in the company.

Qualcomm Ventures also participated, as did Dropbox CEO Drew Houston and Zynga co-founder Mark Pincus.

What many missed in all the excitement, however, was that the impressive figure had been raised over multiple funding rounds dating back likely as far as 2013.

The news was all the more mysterious since the California-based company was still not yet publicizing its business plans.

Observers at the time said chip-maker Qualcomm's involvement was a likely sign that mobile technologies could be at the heart of 21's endeavour, but the big reveal was to come later in the year.

March brought further interesting news, when former JP Morgan exec Blythe Masters took a chief executive role at bitcoin trading platform Digital Assets Holdings (DA).

In a statement to the Wall Street Journal, the commodities veteran suggested that blockchain technology could restore confidence and trust in the financial markets, sentiments that would soon find her becoming the veritable figurehead for the rising interest use cases for bitcoin's distributed ledger, the blockchain.

Masters, who had previously been head of global commodities at JP Morgan Chase, told the WSJ at the time:

In the months since, Masters has become known for her work promoting blockchain tech to Wall Street execs, and has turned down an offer from Barclays to stay at DA.

Still, it was ultimately a mixed year for the DA team, with reports asserting the startup is struggling to raise funding while criticizing the strength of its technical product.

April saw MIT Media Lab announce the launch of Digital Currency Initiative, a three-pronged program aimed at increasing awareness of the technology on campus while providing research to promote policy and standards initiatives.

The news was embellished by the fact that it was to be led by former White House senior advisor Brian Forde, who had previously worked with the administration of President Barack Obama.

Forde explained at the time how the Digital Currency Initiative would seek to address questions regarding the technology's security, scalability and privacy, while convening governments and nonprofits "to research and test concepts" related to its use.

Soon after, Bitcoin Core developers Gavin Andresen, Wladimir van der Laan and Cory Fields joined the project, at a time when their previous financial supporter, the Bitcoin Foundation, was undergoing financial difficulties.

Brian Forde said the move would help bring stability to development team, something he suggested had been lacking in recent years as the foundation had been rocked by scandals.

Later in April, global stock market giant Nasdaq went public with its explorations into how a blockchain solutions could change the way shares are transferred and sold.

While Nasdaq was simply "the latest" big financial group to advertise its interest at the time, it would soon become the most prolific in terms of stoking public interest in its blockchain R&D.

The company would later reveal it was trialling the technology in Nasdaq Private Market, a capital marketplace launched in January 2014, eventually debuting the proof-of-concept at Money 20/20 in November of that year.

In subsequent interviews, Nasdaq has hinted that it is exploring more use cases for the technology and that its interest is only in its infancy.

This enthusiasm also appears to be present throughout the organization, with Nasdaq chief executive Robert Greifeld even telling The Wall Street Journal:

On 29th May, Ross Ulbricht was sentenced to life in prison without the possibility of parole for the operation of Silk Road, the now-defunct online dark market.

The sentence was handed down by US District Judge Katherine Forrest in New York, capping roughly a year and a half-long legal process that saw multiple bitcoin auctions and the shock indictment of two federal agents involved in the investigation.

In addition to the prison term, Ulbricht was ordered to pay $183.9m to the federal government, an amount tied to proceeds related to the operation of Silk Road.

Ulbricht, who ran the marketplace under the name Dread Pirate Roberts, was convicted in February on seven charges related to narcotics distribution, computer hacking and conspiracy.

The severity of the sentencing quickly set off a firestorm of comment and criticism, with debates centering on the alleged hypocrisy of the federal government and the morality of its handling of illicit Internet crime in context of its actions against the traditional financial sector.

Such criticisms, however, were interspersed with live drama, as standing outside of a New York courthouse, Lyn Ulbricht voiced concern for her son Ross Ulbricht’s safety as he left for a maximum security prison.

After months of relative calm, the price of bitcoin spiked to a relative high of $257 on 17th June.

Some in the community sought to tie the market movement to the fact that that Greece was, at the time, likely to default on its debt obligations and exit the eurozone (the 'Grexit' as it had been dubbed).

The international press seized on the claims, but were the two actually linked?

The narrative was not a new one for the bitcoin space, given that digital currencies are one of the few assets that can act as a hedge against fiat currency fluctuation. Similarly, many in the bitcoin community had correlated the rising interest in bitcoin in 2013 with severe economic issues in Cyprus, past precedent that gave momentum to the theory.

However, many prominent members of the bitcoin space had doubts that any real links existed between the two situations, and that Greeks were unlikely to turn to bitcoin as a safe-haven asset.

UK Digital Currency Association board member Paul Gordon suggested at the time, while a convenient narrative, there was little evidence to suggest the timing was anything but coincidental or that activity in Greece is actually at the root of the movement.

Others startups took advantage of the attention, with firms like Coinbase seeking to advertise their services more intently to Greek users.

After more than a year of waiting, the bitcoin and blockchain industry finally saw the passage of the first state-specific licensing regime for digital currencies in June.

The long-controversial regulation was nonetheless heralded as a major milestone among major financial news outlets, one that precipitated a slew of other important developments.

Soon after, bitcoin exchanges itBit and Gemini launched services in New York, though they did so with banking charters rather than BitLicenses. Later, Circle Internet Financial secured what has been to date, the only license issued in the state.

Elsewhere, there was a predictable series of events with bitcoin companies pulling out of New York, blaming the costs of compliance.

Since then, technology advocates have continued to argue the law was still too restrictive for a nascent industry, prompting other US states to take different paths to regulating the industry.

Following its passage, California and North Carolina have both started, and shelved, plans to introduce similar measures.

Mid-August saw a controversial attempt to resolve the fiery bitcoin scalability debate, when two of bitcoin's best-known developers – Gavin Andresen and Mike Hearn – 'forked' a version of the software that helps run the network.

The changes to Bitcoin XT (a patch that sits over Bitcoin Core) were written as a way to 'opt out' of bitcoin's 1MB block size limit, which currently limits the number of transactions that can be processed by the digital currency's mining network roughly every 10 minutes.

Without change, the network can handle around 3-7 transactions per second on a sustained basis, and the average by mid-June had been 1.2 t/s. However, that's not to say there wasn't impetus for action.

Impromptu stress tests had demonstrated that by overloading the network with high numbers of transactions, it was possible to cause significant delays in transaction confirmation.

Reaching the so-called 'capacity cliff' (when transactions exceed the capacity of the network) could either create a competitive market for transaction fees or destroy the robustness of the network completely, depending on who you ask.

Increasing bitcoin's block size – a 'quick fix' for the issue – carries its own long-term implications for the network, which some argued would make the network more centralised and, thus, less trusted.

While anyone can run XT, the new rules will only be triggered when 75% of bitcoin miners have done so. In effect, it was a novel way to let people actually using and supporting the network vote on the matter.

There were numerous critics of the changes, however. Bitcoin Core developer Peter Todd, for one, said at the time that the standard 95% threshold for soft-forks was chosen for good safety engineering reasons, and that 75% was "very low".

Pieter Wuille, another Core developer, told CoinDesk he also had concerns:

'Theymos', moderator of Reddit's r/bitcoin forum, even banned talk of XT claiming that as a fork of Bitcoin Core, XT should be classed as an 'altcoin' or a 'forkcoin', similar to litecoin.

On 9th September, startup Chain announced it had raised $30m in new funding from investors including Visa, Capital One and Fiserv – an impressive figure that revealed the growing recognition of the advantages of blockchain technology.

French telecom giant Orange SA contributed to the round, as did Nasdaq, which has been working with Chain, and Citi Ventures.

The funding all but cemented Chain as the company to watch in the industry, as it had seemingly found a viable business model at a time when many startups were struggling to earn revenues amid declining interest in bitcoin trading.

Chain would go on to debut four proofs-of-concept at big-box financial conference Money 20/20, all but stealing the show from its competition.

First outed by CoinDesk for its ambitions to build a blockchain consortium in July, it was tough at first to tell how successful R3 would be at enlisting enterprise organizations in its work.

Was it an R&D workshop? A consultancy? Or would it be offering a product of its own? While R3's exact strategy is still a bit unclear, what's not is that it will have tremendous support from financial incumbents.

The turn of the tide came in mid-September nine major investment banks, including JPMorgan Chase and Goldman Sachs, partnered with the startup. Many on the list had previously announced independent efforts to study blockchain tech, and the banks were said to be investing money in R3 as part of the effort.

Late September saw 13 more banks sign up – including Citi, HSBC and Bank of America Chase – followed by BNP Paribas, Canadian Imperial Bank of Commerce, ING, MacQuarie and Wells Fargo in November, and another 12 in December that included Banco Santander.

In total, R3 now says 42 of the world's banks have joined the group.

The mysterious and extremely well-funded bitcoin startup 21 Inc made an official announcement for its upcoming bitcoin product in May, stating at the time that its market strategy would focus on distributing bitcoin mining chips embedded in consumer and enterprise hardware devices.

However, it wasn't until late September that it finally started accepting pre-orders for an actual consumer device – the 21 Bitcoin Computer – and 16th November that it actually went on general sale on Amazon.

Retailing for $399.99

, the 21 Bitcoin Computer includes a custom mining chip, a datacenter backend and a custom Linux-based operating system.

The firm made it clear that it did not intend for its units, which contribute to transaction processing on the bitcoin blockchain, to be tools for speculative bitcoin mining. Instead, the units were aimed to provide a "stream of bitcoins" for use in apps and services.

21 Inc, however, struggled somewhat to communicate the product's advantages even to its target consumers in the development community, and as of the end of 2015, seemed intent on relying on word-of-mouth advertising to propel its project rather than more expensive or articulate advertising campaigns.

Reports from Wired and Gizmodo on the 9th December shocked the bitcoin world with claims that they had possibly identified the pseudonymous creator of bitcoin, Satoshi Nakamoto, as Australian entrepreneur Craig S Wright.

Dave Kleiman, a US computer forensics expert who passed away in 2013, was also said to have been significantly involved in the development of the digital currency.

According to Wright's LinkedIn account, he has worked with a series of companies including Hotwire Pre-Emptive Intelligence Group – the firm behind an effort to create a bitcoin-based bank called Denariuz and later ran into problems with the Australian Tax Office.

In its exposé, Wired cited "an anonymous source close to Wright" who provided a cache of emails, transcripts and other documents that pointed to Wright's role in the creation of bitcoin.

Gizmodo

, meanwhile, said it had been provided with a cache of documents, which it had corroborated in interviews, from someone claiming to have hacked Wright’s business email account.

Wired presented its evidence with caution, raising the possibility that the information might have been fabricated – perhaps even by Wright himself, and other news outlets soon began picking apart the story's inconsistencies.

Still, the idea that the Wright 'revelations' are nothing but a hoax has been aired by other observers, though the compelling nature of the published evidence will no doubt fuel speculation for some time to come.

What were your biggest stories of 2015? Let us know in the comments below.

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