Final answer:
The Health Insurance Portability and Accountability Act (HIPAA) of 1996 is the key piece of legislation that protects patient confidentiality by requiring strict confidentiality of patient records.
Step-by-step explanation:
The key piece of legislation that protects patients' confidentiality is the Health Insurance Portability and Accountability Act (HIPAA), passed into law in 1996. This act sets the standards for the protection of patient information, requiring businesses such as insurance companies and healthcare providers to maintain strict confidentiality of patient records. This legislation plays a critical role in ensuring that patient's health information is not disclosed without their consent, emphasizing privacy rights within the healthcare industry.