My advice from my experience, be honest and straightforward. If you think we don't understand what you're trying to accomplish, give us more information and reissue your question in a way that it sounds more above board.
Perhaps the issue is that you cannot disclose your identities while you're working for Capgemini. I hope you are not violating any agreement made with Capgemini and the further advice is not feasible if you are. There are companies that startup and even start to grow under the radar. In this case, there are two prime choices:
1. Be honest with your media outlets, explain that you are under the radar and not ready to be identified but you have a great story to be told and that they can be on the inside track if they give you assurance that they will report on you anonymously. They will still need to vet you and you cannot reasonably stay invisible to credible media outlets, but if they say they will report without naming the company or source, you can usually trust them to do so. As far as vetting, they will likely want to make sure you are not breaking agreements or laws so that they do not come under undue scrutiny. You may have to show them documents if doing so does not violate any agreements you have.
2. Perhaps you have one partner who is not subject to the same restrictions as the rest of you. That partner can disclose the under the radar company's mission and whatever message you want to get out without naming the company but probably quoting your public partner.
You're starting from a tough stance. I hope you can rephrase your question in a way that I don't read it as somewhat underhanded.