SpiderOak founder here...

A few cryptographers have noticed SpiderOak's marketing term Zero Knowledge is inconsistent with the academic definition. Maybe it doesn't mean what we think it means[1]? SpiderOak was one of the first companies to use this phrase commercially and the need has only grown stronger.

At the heart of the issue is the difficulty for end users to decipher the terms cloud vendors use to describe their security. Doing so would require discrimination between transport encryption, data encryption, meta data encryption, encryption at rest vs. in motion, and then most importantly evaluate key management and access. This vocabulary is foreign to most folks. Vendors often exploit the inaccessibility of these topics to make a series of statements that, while often factually correct individually, together create a false sense of privacy.

SpiderOak launched a online backup product for Linux, Mac, and Windows in 2007. The competitors were companies like Xdrive, Mozy, Carbonite and SugarSync. Each claimed that customer data was fully encrypted. Even the most credible journalists writing for well funded publications with fact checking budgets were fooled and repeated these misleading claims to end users. [2]

In 2009 when Dropbox launched, they made misleading claims about the encryption of customer files and their internal ability to access customer's data or provide that data to 3rd parties, leading to a well publicized FTC deceptive trade practices complaint. [3] The deception had been so effective that leading software engineers were shocked to discover Dropbox had full access to the data they had stored online. [4]

In response to customer requests on one of their forums, Mozy explained why it would be "impossible" for a storage service to protect users' privacy by encrypting the file and folder names customers store in a way Mozy could not read. SpiderOak customers had benefited from the impossible for years.

Recently Slack made the unbelievable claim on Twitter that their service includes end to end encryption (it doesn't.) Perhaps they mean from your end to their end?

Lately there's a new phrase "customer managed keys" used by cloud providers, which sounds really great, but is typically just elaborate hand waving that ultimately allows the vendor and their staff the same level of data access as if it were not encrypted.

In 2007 we found ourselves frequently explaining "we don't know the names of your files, the names of your folders, the date they were created or last modified or accessed, their size, their checksums or hashes... in short we know nothing about your data except how much you store." We started using the phrase Zero Knowledge as a headline to this long explanation.

It's important to recognize that cryptographers already understand encryption and the terminology is intended for everyday folks. When I'm speaking with a technologist about how SpiderOak products work, I would typically use the phrase end to end encryption.

If we want to end mass surveillance, the only way this can happen is through viral adoption of end to end encrypted products and services. Great UX, education, and terminology are powerful tools, and unlike phrases involving the word "encryption", to my knowledge no company has yet been shameless enough to deceptively use the term Zero Knowledge.

[1] https://www.youtube.com/watch?v=G2y8Sx4B2Sk

[2] http://allthingsd.com/20080403/sugarsync-offers-the-best-met...

[3] https://www.wired.com/2011/05/dropbox-ftc/

[4] http://tirania.org/blog/archive/2011/Apr-19.html