Secret, a mobile-first social network that allows people to share their personal thoughts and beliefs with others anonymously, raised $25 million in a second round of funding that values the company at $100 million and positions it to take on mainstream social networks.

Secret also said it would add Facebook integration to enable members to find their friends on the giant social network. Previously, the site only used members’ phone contacts for that purpose.

Secret provides anonymity within a circle of trust. People post short secrets accompanied by images for others to share and comment upon. The service has already proven popular with techies, who post rumors about comings and goings in business. Secret is betting that anonymity will have broader appeal. A similar social network, Whisper, recently raised $39 million.

Writing on the blog of venture capital firm Redpoint Ventures, which is backing Secret, former Twitter executive Ryan Sarver said Secret could be the next Twitter:

While I was at Twitter, I saw the incredible role pseudonymity and anonymity played in allowing people to broadcast and express themselves freely. From whistleblowers, to citizen journalists trying to get information out from under oppressive regimes, to the deeply personal, to the funniest parody accounts, anonymity allows expression that wouldn’t have otherwise happened.

But where Twitter is about putting a range of ideas out there for public consumption, Secret is much more about having an unfettered conversation with people closely connected to you, where individuals are free to express themselves without fear of embarrassment or judgment. We think it’s a fundamental and important part of social connectedness and we’re incredibly excited to back David Byttow, Chrys Bader, and the rest of the Secret team.

Secret Index’s Danny Rimer is joining the board of directors.  Secret, which was founded in the fall of 2013, has raised over $35 million in VC funding.  Secret said it will use the money to compete with Whisper and take a run at Snapchat.

Another new board member, Danny Rimer of Index Ventures, offered his views on his blog.

[We] believe that Secret will become a massive social phenomenon with billions of users around the world…Secret is addictive, engaging, and unique – and its tremendous growth is a testament to the fact that it is addressing an important human need.

Rimer cited three reasons his firm is investing. They include the human need for anonymous expression, the management team’s ability to manage explosive growth and the potential for Secret to scale into other markets, such as online suggestion boxes and curated content.