When You Should Use TDE vs Always Encrypted (2024)
Microsoft SQL Server and Microsoft Azure SQL Database offer two complementary encryption options: Transparent Data Encryption (TDE) and Always Encrypted. This blog post will help you decide when to use TDE versus Always Encrypted, and when to combine them for a “defense in depth” security and compliance strategy.
Transparent Data Encryption (TDE) protects data at rest, such as backups on physical media. It prevents access to data in scenarios like improper disposal of disk drives or attempts to restore databases from snapshots or copies.
TDE helps companies comply with regulations that mandate encryption of data at rest, such as HIPAA and GDPR. As a general rule, it’s appropriate to enable TDE for any SQL database, unless its data has no protection requirement at all.
TDE encrypts the full SQL Server database in a manner that doesn’t require changes to the application. Encryption and decryption of the data and log files are performed in real-time.
However, TDE offers no protection for the data once it resides in memory. This leaves it vulnerable to “insider threats” and credential theft-related access from administrator (DBA) accounts, such as sysadmin, or other roles/applications that are authorized to access the database.
To protect data in memory from identity/credential-based attacks, businesses can use Always Encrypted, which encrypts sensitive data in specific database columns in memory or “in use” during computations. The data remains protected even if the entire system is compromised, e.g., by ransomware. Attacks that involve scanning the memory of the SQL Server process or attempting to extract data from a memory dump are also ineffective against Always Encrypted.
Always Encrypted allows SQL Server users to reduce the risk of storing data in the cloud, or to leverage third-party vendors for DBA services without violating compliance requirements.
However, Always Encrypted relies on a client-side database driver within an application to encrypt the requested data before sending it to the database and to decrypt encrypted data in query results. Reliance on a client-sideWindows driver means that applications may require changes to work with Always Encrypted requirements and restrictions. For example, Always Encrypted supports only a few simple operations on encrypted database columns. This tends to limit its use to only higher-risk sensitive data, such as:
Personal data like customer names and credit card numbers, especially in regulated industries
To improve security when outsourcing DBA services
To improve security of data in transit and in use beyond what SSL alone can offer
A good rule of thumb for Always Encrypted is it works best to protect sensitive data that you need to store but don’t need to search on or display to application users. Beginning with SQL Server 2019 (15.x), Always Encrypted supports secure enclaves, which removes some of the limitations on operations you can perform on encrypted data.
To create a “defense in depth” or layered encryption protocol for your data, TDE and Always Encrypted can be used together alongside Transport Layer Security (TLS).
In this scenario, TDE acts as the defensive front line by encrypting the full database at risk, and may suffice to meet compliance requirements. TLS then encrypts data as it is transferred over a network. Finally, Always Encrypted protects the most sensitive data from privileged user attacks, malware that has compromised the database environments, and other threats against the data while it is in use.
TDE works with SQL Server 2008 and above as well as Azure SQL Database, but requires SQL Server Enterprise Edition. Always Encrypted works with all editions of SQL Server 2016 (13.x) SP1 and above, plus Azure SQL Database. Both TDE and Always Encrypted are free in Azure SQL Database.
Want to talk with a database security expert before you implement TDE versus Always Encrypted? Contact Buda Consulting to schedule a free consultation.
Always Encrypted is also supported in both Azure SQL Database and Azure SQL Managed Instance. In general, TDE is best used when protecting data at rest
data at rest
Data at rest in information technology means data that is housed physically on computer data storage in any digital form (e.g. cloud storage, file hosting services, databases, data warehouses, spreadsheets, archives, tapes, off-site or cloud backups, mobile devices etc.).
To simplify: TDE secures all of the database files on disk, hence the term "at rest". Since encryption and decryption are done by the database engine, it's transparent to all clients. Always Encrypted is more granular, specific data elements/columns store encrypted data which requires a "key" to translate.
For applications that need to perform pattern matching, use comparison operators, sort, and index on encrypted columns, you should implement Always Encrypted with secure enclaves. Query statements that trigger computations involving both plaintext and encrypted data aren't allowed.
When to use Transparent Data Encryption. Transparent Data Encryption (TDE) protects data at rest, such as backups on physical media. It prevents access to data in scenarios like improper disposal of disk drives or attempts to restore databases from snapshots or copies.
One disadvantage of TDE is that it does not protect data in transit. Data is only encrypted when it is at rest in the database. If data is transmitted over a network, it can be intercepted and read by an attacker.
TDE helps protect data stored on media (also called data at rest) in the event that the storage media or data file is stolen. Oracle Database uses authentication, authorization, and auditing mechanisms to secure data in the database, but not in the operating system data files where data is stored.
Asymmetric and symmetric encryption are both better suited to specific scenarios. Symmetric encryption, which employs a single key, is preferable for data-at-rest.
Cell-Level Encryption (CLE) Another method for encrypting your data is via cell-level encryption (CLE) to protect and secure your data at Rest. Similar to Always Encrypted, CLE is used to encrypt specific columns or cells.
Differences Between Randomized and Deterministic Encryptions. The initial Always Encrypted offer allowed the choice of two encryption types: Randomized and Deterministic. If you require the ability to do equality comparison and indexing, you must choose Deterministic.
Generally speaking, there are two contexts when you would use encryption: when it is “in transit” or when it is “at rest”. What “in transit” means in this context is when you send it somewhere else via the web, in email, or any time you want it to be somewhere other than just on your own device.
TDE protects data at rest, which is the data and log files. It lets you follow many laws, regulations, and guidelines established in various industries. This ability lets software developers encrypt data by using AES and 3DES encryption algorithms without changing existing applications.
Always encrypted is completely transparent to the applications.The client application needs to be heavily modified to support column-level encryption. An Always Encrypted-enabled driver needs to be installed on a client computer to handle encryption and decryption transparently.
What is a disadvantage of always sending encrypted messages? Takes longer for messages to be sent/received since it needs to be scrambled and then unscrambled. A digital certificate is required as it contains part of the key/special code.
TDE only protects you against lower levels of access. The fact that an admin can get around the protection is an inevitability of many forms of encryption. TDE is managed by an administrator who has the sysadmin permissions on the database instance. They can enable TDE, they can disable TDE.
TDE encrypts the storage of an entire database by using an industry-standard AES-256 algorithm. It encrypts the data files, transaction log files and backups, making it an ideal choice for compliance with regulations such as HIPAA and PCI-DSS.
Always Encrypted is a client-side encryption technology that ensures sensitive data (and related encryption keys) are never revealed to the SQL Server or Azure SQL Database.
Transparent Data Encryption (TDE) is an essential security feature for databases, designed to encrypt data at rest—meaning the actual database files on disk. It is widely implemented in database management systems by major vendors such as Microsoft, IBM, and Oracle.
Gmail Confidential Mode does add some extra security features designed to protect your emails from unwanted recipients. It doesn't use the same level of encryption as S/MIME but is more secure than sending an email without using Confidential Mode at all.
Introduction: My name is Errol Quitzon, I am a fair, cute, fancy, clean, attractive, sparkling, kind person who loves writing and wants to share my knowledge and understanding with you.
We notice you're using an ad blocker
Without advertising income, we can't keep making this site awesome for you.
