We don't have a problem with symmetric encryption. We have a problem with the key being stored on your servers, effectively nullifying encryption. Now, I'm not

We don't have a problem with symmetric encryption. We have a problem with the key being stored on your servers, effectively nullifying encryption. Now, I'm not saying it's an easy problem; kudos to you for tackling it. It's just that - if you have the keys to the payload - if you don't provide open-source client code then no one can honestly trust your service. Don't forget that what you're primarily doing with is trust.