The goal in this paper is to enable collaboration in the co-design of engineering artifacts when participants are reluctant to share their design-related confidential and proprietary information with other co-designers, even though such information is needed to analyze and validate the overall design. We demonstrate the viability of codesign by multiple entities who view the parameters of their contributions to the joint design to be confidential. In addition to satisfying this confidentiality requirement, an online co-design process must result in a design that is of the same quality as if full sharing of information had taken place between the co-designers. We present online co-design protocols that satisfy both requirements, and demonstrate their practicality using a simple example of co-design of an automotive suspension system and the tires. Our protocols do not use any cryptographic primitives they only use the kinds of mathematical operations that are currently used in single-designer situations. The participants in the online design protocols include the co-designers, and a cloud server that facilitates the process while learning nothing about the participants confidential information or about the characteristics of the codesigned system. The only assumption made about this cloud server is that it does not collude with some participants against other participants. We do not assume that the server does not, on its own, attempt to compute as much information as it can about the confidential inputs and outputs of the co-design process: It can make a transcript of the protocol and later attempt to infer all possible information from it, so it is a feature of our protocols the cloud server can infer nothing from such a transcript.