San Francisco-based Coinbase, a market for trading bitcoin and other cryptocurrencies, said Thursday it has signed a seven-year lease for a downtown Portland office and plans to hire up to 100 people.

Coinbase announced last month it would open a customer service office in Portland amid frustrations over delayed transactions and reports of poor service. The Portland Business Journal reported in May that Coinbase will be in a building just south of Pioneer Courthouse Square.

Economic development agency Greater Portland Inc., which helped recruit Coinbase, said the company received no public incentives for the new office.

Coinbase, which claimed $1 billion in revenue last year, is a trading platform and storage service for a variety of digital currencies that exist only online.

Cryptocurrencies are decentralized alternatives to conventional, government-issued currencies like the dollar. Enthusiasts say they are secure and anonymous, with features that reduce transaction costs.

Skeptics doubt bitcoin and other digital currencies have underlying value and worry they may represent a bubble, with widely fluctuating prices. But mainstream financial institutions have begun exploring their utility and a growing number of online retailers accept.

The currencies are essentially an online record in a giant online ledger, called the blockchain. Cryptocurrency holders keep their money in online wallets and spend the digital money electronically.

Portland's tech economy is dominated by outposts of companies from larger cities, many seeking to escape the high wages and operating costs in Seattle, San Francisco and New York. That's especially true for less technical functions such as customer service, which generally earn lower wages than engineering roles.

Airbnb, Squarespace and Yahoo all have customer service centers in the Portland area.

-- Mike Rogoway | twitter: @rogoway | 503-294-7699