Probably stored under the same security infrastructure as Gmail and hangouts messages.

Which, IIRC, means no human is given direct access without the account holder's permission. Algorithms are allowed access, but only if they emit data that is similarly secured, or emits data in aggregate (where, I think, aggregate was defined as 100k+ users per aggregate data point)

It's extremely hard for a Googler or product team to do something directly nefarious, but you do have to trust Google's privacy infrastructure.

And that is exactly why open IM protocols and 3rd party clients are so important.

If both you and your correspondents do use 3rd party IM client ([1], [2], etc), then just run OTR2 or OMEMO on top of the protocol, and let google store whatever it pleases - it's not going to be much use for them.

[1] https://pidgin.im/

[2] https://conversations.im/

I've seen this sentiment in a couple of places now -- and the news media and non-technical folks seem to refer to "encryption" very loosely to mean "protected in the way I want it to be protected at the times I want it to be protected".

Can we please use technical terms with precision?

You can have data encrypted at rest and in transit that is still accessible to the provider and the fact that the provider can decrypt it for processing doesn't make it any less "encrypted". There is not a total ordering of encryption or security schemes.

If you would like to say that the data isn't end-to-end encrypted such that it is opaque to the service provider -- say that. Don't say it isn't meaningfully encrypted.

Perhaps it's some kind of homeomorphic encryption scheme. Hey it technically leaves the original message encrypted!

They could be using some form of homomorphic encryption here, in which case it would still be meaningfully encrypted.

There is actually some research work on this front because it is highly valuable to analyze some data but not have access to it.

However, it's better just to encrypt everything and not be tempted by the advertising surveillance dollars.

  So, not meaningfully encrypted at all then?

One could also think of it as your private key being with (1) you, (2) Google.

It's in safe hands ;-)