Assurance
Grounds for confidence that the other four security goals (integrity, availability, confidentiality, and accountability) have been adequately met by a specific implementation. "Adequately met" includes (1) functionality that performs correctly, (2) sufficient protection against unintentional errors (by users or software), and (3) sufficient resistance to intentional penetration or by-pass.
Source:
[NIST SP 800-27 Rev. A] Stoneburner, G., Hayden, C., Feringa, A., Engineering Principles for Information Technology Security (A Baseline for Achieving Security), NIST Special Publication 800-27 Rev. A, June 2004.
