Direct Secure Messaging (DSM) is a protocol designed to facilitate the secure exchange of health information over the internet. Utilizing digital certificates and Public Key Infrastructure (PKI), DSM ensures that messages are encrypted and can only be accessed by intended recipients. It is widely used for transmitting sensitive health data, such as patient referrals and care coordination documents, between healthcare providers. DSM is integrated into certified Electronic Health Record (EHR) systems, providing a standardized method for secure communication across diverse healthcare organizations.