Used in formal, business, or technical contexts to describe the property of information being kept secret or restricted.
This document has high confidentiality, so please handle it with care.
情報の機密性を守るために、パスワードを定期的に変更しています。
To maintain the confidentiality of information, we change passwords regularly.
機密 means 'secret' or 'classified information', whereas 機密性 is the abstract noun meaning 'confidentiality' or the property of being secret.
content confidentiality
message flow confidentiality
traffic flow confidentiality
Compound of 機密 (secret, classified) and 性 (nature, property). The word is a modern Sino-Japanese formation used in business and legal contexts.