The promise of digital wallets has fueled the conversations and hopes of financial technologists for years. But there are many obstacles to having those dreams realized, including the fact that more consumers need to know that digital wallets exist.

Indeed, only 51 percent of U.S. consumers said they are aware of wallets other than PayPal, according to a comScore Inc. study published this week. comScore, which evaluated eight brands in its research, defines digital wallets as virtual copy of the contents of a consumer's physical wallet to facilitate online or offline retail.

PayPal, which has existed since the 1990s, owns brand awareness for digital wallets, with 72 percent of those polled reporting they knew of its service. Compare that figure to Google Wallet, which received the second highest awareness score of the digital wallet providers evaluated; only 41 percent of respondents said they were aware of it. The numbers only got worse from there for the six other brands comScore evaluated: MasterCard PayPass Wallet (13 percent), Square Wallet (8 percent), by Visa (8 percent), ISIS (6 percent), Lemon Wallet (5 percent) and LevelUp (5 percent).

The study is based on a panel of one million U.S. consumers and two additional surveys of more than 2,000 U.S. Internet users conducted in November 2012.

"Low awareness, understanding of benefits and availability among retailers are among the key barriers to adoption of digital wallets," said Andrea Jacobs, comScore payments practice leader, in a press release. "While these impediments may seem like a steep hill to climb, we have seen this story play out before in the financial services industry. There was a time when consumers were reluctant to use ATMs for similar reasons, and today, look at how far we've come since the 1970s and 1980s."