A man walks past a Bitcoin symbol on a window of the offices of the bank 'La Maison du Bitcoin' in Paris.

It's a bit of a mystery. Interest in bitcoin and the blockchain has been building to a fever pitch, but mergers and acquisitions in cryptocurrency have been almost nonexistent.

It's not for lack of interest.

Meltem Demirors, director of development for Digital Currency Group, is one of many who believes that a bank, an exchange, or a major investment firm will make major acquisitions in the cryptocurrency space in 2018.

She said many boards and information technology departments are looking around. "The question is, can I build it, or do I need to buy it?" she said. "Talent is scarce, time to development is long, and if your board is breathing down your neck acquisition may be the best strategy."

Hunter Horsley, the CEO of Bitwise Asset Management, which recently launched the first cryptocurrency index fund, said many of the bigger firms are still trying to figure out how real all this is.

"The people you might expect to be on the acquiring side are still trying to figure out if this is legitimate," he said. "There's still some reputational risk that's present, and among some there are even some moral questions about the whole space that remain."

Michael del Castillo, who writes on cryptocurrencies for Coindesk, also said he believes that some large deals will be coming in 2018. "We have been wondering what the first billion dollar exit will be, the first one to be acquired for $1 billion, but very little has gone past the speculation phase," he said.

Cryptocurrency exchanges are the most attractive businesses. "They are spinning out a lot of cash," he says.

He points to a recent deal in South Korea, which has emerged as a global player in cryptocurrency trading. In September, Nexon, a Korean gaming firm, purchased a 65 percent stake in Korbit, one of the top three cryptocurrency exchanges in South Korea, at a sale price of 91.3 billion Korean won (roughly $80 million).

While there have been few outright purchases, blockchain technology-based companies are raising money, though mostly among venture capital firms. Coinbase, the most popular digital currency exchange, completed a $100 million Series D funding in August and has raised a total of $217 million since 2012. Investors include Andreessen Horowitz, USAA and the New York Stock Exchange.

Investments from corporate America have been small, but are growing.

A recent report from CB Insights notes that Citi, Goldman Sachs and JPMorgan Chase have all made direct investments in Axoni, which is working on applying blockchain technology to banking.

Visa, Nasdaq, Citi and Capital One have made direct investments in Chain, which was created to allow financial institutions to create and store digital assets on private networks.

Google has also made investments in Ripple, which provides financial institutions with money-transfer technology, as well as LedgerX, a cryptocurrency deriviatives platform.

Japanese venture capital firm SBI Holdings has also actively invested in cryptocurrency exchanges Kraken and Ripple.

Still, the numbers have been relatively small. CB Insights notes that since 2012 corporations have participated in more than 140 investments, but to the tune of just $1.2 billion.

Horsley says to give it time. "Banks are not yet in a space where they are ready to endorse billions of dollars in cryptocurrency," he said.

He also notes that some of these companies may not even want to be part of the old-school financial system.

Brian Kelly of Brian Kelly Capital says that even if they were made an offer, many might not accept. "A lot of these companies are making so much money, that they are not for sale," he said.