The guys behind OkCupid and SparkNotes are making an encrypted competitor to Slack

In 2015, the pair cofounded Keybase, an encryption-focused startup. On Monday, it announced an early version of Keybase Teams, a chat app designed for use by teams and in the workplace — much like Slack, the buzzy Silicon Valley app popular with startups and media companies and worth $5.1 billion. (We saw the news via Fortune.)

But there's a key difference: Keybase Teams is end-to-end encrypted, meaning it's theoretically impossible for anyone to snoop in on conversations — including Keybase itself. Slack, meanwhile, encrypts its messages, but only to its own servers.

The pair directly drew comparisons to Slack in a blog post announcing the new app, while bigging up the benefits of its encryption. It offers significant security advantages, they argued, making users less vulnerable to hackers: "Keybase teamwork is end-to-end encrypted, which means you don't have to worry about server hacks. Alternatively, you can lie awake at night...fearing a breach of your company's messaging history. What if your team's history got stolen from Slack and leaked or published? The legal and emotional nightmare."

In theory, it's an attractive proposition to organisations handling sensitive information (like a media company, say), who might be reluctant to relinquish control over the security of a key part of their infrastructure.

The user interface looks largely similar to Slack, with a mix of public and private channels that teams can chat in, alongside one-to-one direct and group messages. (Slack itself is, of course, styled after traditional Internet Relay Chat (IRC) channels.)

It’s also not explicitly targeted at companies and their teams. The startup suggested teams might be based around "any topic": Music, cryptocurrencies, mothers in a particular neighbourhood of New York, or just a single family.

Heres a screenshot that Keybase shared:

Right now, Keybase Teams is very much a work-in-progress, still in an "alpha" build. For the next two months or so, any team administrators will have to use command line instructions to manage the software.

It's free for anyone to use now, though Keybase says that "if teams take off, we'll charge for larger teams. Nothing we're offering for free now will flip to a pay model, so if you make a 500 person team now and start using it, you won't someday be faced with a credit card screen just to get your files or messages."

Krohn and Coyne, both based in New York, founded study guide site The Spark, which later became SparkNotes, in 1999. They then went on to found OkCupid, the famous dating site in 2003, with Krohn leaving the company in 2012 and Coyne in 2013.