AZ-500 Microsoft Azure Security Technologies Exam

Assess Use Cases and Constraints for Always Encrypted

Always Encrypted is a feature in Azure SQL Database designed to protect sensitive data in use from high-privileged or unauthorized users. It encrypts data on the client side so that even database administrators or cloud operators see only ciphertext. This approach ensures strong separation of duties by keeping encryption keys separate from the database engine. With Always Encrypted, sensitive values never appear in plaintext on the server or in memory.

Selecting Always Encrypted starts with assessing column-level data sensitivity and regulatory compliance obligations. You should encrypt only the columns that store PII, payment card details, or healthcare information to reduce overhead. To plan your implementation:

• Tag and classify columns according to sensitivity.
• Align encryption with standards like PCI DSS or GDPR.
• Balance data protection needs against possible query limitations.

Client-side driver compatibility is essential for transparent encryption and decryption. Applications must use supported ADO.NET, JDBC, or ODBC drivers that can communicate with Azure Key Vault. Before deployment, verify that all client drivers support:

• Secure key retrieval.
• Local encryption and decryption operations.
• Compatibility with BI or ETL tools, as some services may not handle encrypted columns.

Implementing Always Encrypted introduces performance and functionality trade-offs due to limited operations on encrypted data. Key constraints include:

• Deterministic encryption only supports equality comparisons and joins.
• Randomized encryption prevents any computation, such as range scans or pattern matching.
• Indexing on encrypted columns is restricted.
  Plan to refactor stored procedures, views, or triggers so that sensitive processing occurs on the client side or through alternate designs.

Effective key management is critical to maintain security and compliance. Use Azure Key Vault to store Column Master Keys (CMKs) and enforce strict role separation. Best practices include:

• Assign security admins to create and rotate physical keys in Key Vault.
• Let DBAs manage Column Encryption Key (CEK) metadata without direct key access.
• Maintain a minimal number of CMKs and CEKs per database.
• Use online encryption during key rotation to reduce application downtime.

Conclusion

When deciding to use Always Encrypted, focus on protecting highly sensitive columns and meeting regulatory requirements while managing performance trade-offs. Ensure all client applications use supported drivers and can perform local encryption and decryption. Plan for limited query capabilities on encrypted data by refactoring logic or offloading computation to clients. Finally, implement a robust key management strategy with Azure Key Vault and strict role separation to safeguard your encryption keys.