As the article points out, encryption is an already solved problem. The problem that is, and always has been problematic is key distribution.
Companies that offer encryption products use various mechanisms to allow the sender and the recipient to end up with matching keys. It is surprisingly difficult to do correctly.
It is not enough that the communication stays encrypted from the sender, through the server, and to the recipient. It is also important that no one besides the sender and recipient has the ability to decrypt that communication.
Inky has posted a document entitled "Inky Security White Paper" here: http://inky.com/secure/
Haven't tried the software or given their paper a proper read yet.
Initial thoughts: No forward/future secrecy. Stores user private keys on their server encrypted with user supplied passwords. Their centralized service is trusted for identity. Not sure how users update their secrets if compromised.
Adding proper E2E crypto to legacy email is hard. I don't think they solve it.
Companies that offer encryption products use various mechanisms to allow the sender and the recipient to end up with matching keys. It is surprisingly difficult to do correctly.
It is not enough that the communication stays encrypted from the sender, through the server, and to the recipient. It is also important that no one besides the sender and recipient has the ability to decrypt that communication.