What is the term for sharing knowledge where two individuals each hold part of the critical information needed for a task?

The term you're asking about is accurately identified as "Split Knowledge." This concept refers to a situation in which two individuals each possess a piece of critical information required to complete a task or achieve a goal. This division of knowledge enhances security and helps prevent any single person from having complete control over sensitive information. Split knowledge is often used in areas such as information security and access control, where it is essential to minimize risks by ensuring that no one individual has all the necessary information to carry out a critical function or access sensitive data.

In the context of security practices, utilizing split knowledge can mitigate the risk of fraud, misuse, or unauthorized access, as both parties are needed to collaborate and share their respective knowledge for a secure outcome. This ensures a layer of accountability, as both individuals must work together, thus reducing the likelihood of malicious actions going unnoticed.