A Certificate of Confidentiality (COC) is an official document issued by a government agency or institution to protect the privacy of research participants. It legally prevents investigators and their associates from being forced to disclose identifying information about research participants in any civil, criminal, administrative, legislative, or other proceeding, regardless of whether the proceedings are related to the research. The certificate also prohibits the use of identifying information for any purpose other than research. There are two types of Certificate of Confidentiality: federal and non-federal. Federal Cows are issued by the National Institutes of Health (NIH) and are available for research that is funded by the NIH. Non-federal Cows are issued by other government entities, often state health departments.