This is indeed true for our standalone, open source database (https://github.com/zerodb/zerodb).

However, it is not the case for our Hadoop scheme (nor our future support for structured database). In these cases, there is no round-tripping required. In fact, it's significantly more performant than existing Transparent Data Encryption in Hadoop, from both a latency and key rotation perspective.

We'll likely release a paper describing this new scheme later in the year as well as publish at some conferences.