Always Encrypted or Transparent Data Encryption

Always Encrypted

Pros:

1. Granular Data Protection: Always Encrypted provides column-level encryption, allowing you to selectively encrypt sensitive data fields. This offers more fine-grained control over the encryption process.
2. Client-Side Encryption: Encryption and decryption of data occur on the client-side, ensuring that sensitive data is protected even when it is in transit or stored on the server. This minimizes the exposure of sensitive data to the database administrators or cloud service providers.
3. Application Transparency: Always Encrypted is transparent to the applications accessing the data. The encryption and decryption process is handled automatically by the client drivers, making it easier to implement without significant application changes.
4. Query Support: Always Encrypted supports various query operations, including equality, range, and pattern matching, on encrypted columns. This allows you to perform operations on encrypted data without the need to decrypt it.

Cons

1. Limited Functionality: Always Encrypted does not support all database features and operations. Functions like indexing, sorting, and joining on encrypted columns are limited, which may impact performance and query capabilities.
2. Key Management: Managing encryption keys can be complex, especially when dealing with multiple clients or key rotation. Proper key management practices are crucial to ensure the security and availability of encrypted data.

Transparent Data Encryption (TDE):

Pros

1. Ease of Implementation: TDE is easy to implement as it operates at the database level. Once enabled, the entire database is encrypted, including backups, log files, and tempdb. No application modifications are required.
2. Transparent to Applications: TDE is transparent to applications accessing the database. The encryption and decryption process is handled internally by SQL Server, without any additional configuration or coding needed in the application.
3. Minimal Performance Impact: TDE has a relatively low performance impact on SQL Server. The encryption and decryption operations are performed at the page level, and the additional overhead is usually negligible for most workloads.

Cons

1. Limited Data Protection: TDE protects data at rest, ensuring that physical copies of the database are encrypted. However, when the data is in memory or during data access, it is in plaintext form, leaving it vulnerable to unauthorized access if the server is compromised.
2. Limited Granularity: TDE operates at the database level, meaning that all data within the database is encrypted. It does not provide granular control to encrypt specific columns or data fields within the database.
3. Database Administrator Access: TDE encryption is transparent to database administrators, allowing them full access to the decrypted data. While this may not be an issue in most scenarios, it is worth considering if there are specific compliance or security requirements.