alt Hacker NewsCipherStash founder here.
If a column is encrypted using standard encryption (like AES-GCM) then the values are non-deterministic and fully randomized. That means that if you encrypt the same value twice, you'll get 2 different ciphertexts.
So the query: select * where secret_col == 10
Would actualy be: select * where secret_col == encrypt_aes(10);
And values in secret_col will never match (because the output of encrypt_aes will be different every time, even for the same input).
A common way around this is to use deterministic encryption which eliminates the randomization at the cost of a slightly weaker security model. What leaks is the ability to see if any 2 plaintexts are equal (because they have the same ciphertext) - what you actually want in the case of search.
You have to be careful implementing deterministic encryption though: don't use AES-GCM with a fixed nonce because the scheme completely breaks. You can use CBC mode but then you lose authenticity. We use AES-GCM-SIV (synthetic IV which retains authentication but is secure under a fixed nonce) and HMAC (keyed hashing).
But there are approaches to solving queries like: -- range/order SELECT * FROM foo WHERE x > 10; SELECT * FROM foo ORDER BY x; -- fuzzy text SELECT * FROM foo WHERE name ~ "dan";
These capabilities are all based on public research: For example, order/range uses: https://eprint.iacr.org/2016/612.pdf
Our docs are quite limited at the moment (fixing as quickly as we can!) but you can see the current list of supported queries here: https://cipherstash.com/docs/stack/cipherstash/encryption/qu...
Replies
Don’t use deterministic encryption unless your data is already highly random.
Any adversary who knows the distribution of the plaintext data can guess what your encrypted values are, with accuracy that improves as your sample size increases.
There were a bunch of papers on this 10-12 years ago. (Full disclosure: I was an author on some of them.)
Searchable encryption means you can have encryption and queries (from apps etc) still work for authorized users.
This is all started when I was the CTO of a health-tech and the engineers all had access to patient data. They needed DB access (data migrations, managing backups, reading non-sensitive fields) but not access to the sensitive values. 10m+ patient records - it made me nervous.
Row-level Security (RLS) was a nightmare, it was slow, easy to mess up and could be overridden by DBAs anyway. Plus the application connected to the DB using a service account so RLS was useless for end-user access control.
CipherStash solves the following:
* Hide sensitive data from direct database accessors (authorized or not!)
My original use-case. Direct access to the DB doesn't reveal sensitive data (unless the user also has permission to decrypt a specific record).
* Support or even replace application access controls
Decryption happens in the application layer and is based on end-user identity. That means a gap in application defenses is mitigated by the encryption. If the user can't decrypt the value then they can't access the data.
* Access auditing
Every sensitive data access is recorded (and by who) which is very useful for compliance and incident response. SQL query auditing is great for knowing what queries were run but it doesn't tell you what data was actually returned. Its also blind once data actually leaves the DB and can inadvertently leak sensitive data itself. Using key accesses with non-identifying value IDs to audit decryptions makes the auditing more reliable and super granular.
We have customers who use the tech to prove to their users (often large enterprise) that no internal staff can access the data.
* Agent access to data
The encryption shifts access control decisions down to the data layer on a per-value basis. This is incredibly useful for gating access to agents that need access to data. Every decryption requires authentication (e.g via Supabase Auth, Auth0 etc) and combining it with agent identities (creds issued to agents) means you can not only limit what agents can access, you can also audit exactly what _was_ accessed.
The searchable encryption is the enabler: value level encryption is what makes all of this possible. Searchable encryption means you can have encryption and queries (from apps etc) still work for authorized users.
Hope that helps! I'm so in the weeds I don't know if I explain things that well sometimes!
the OP asked why, you more described the how.
What is the benefit of all this?
What does all this actually solve? Presumably SQL injection might still decrypt contents and order by/where clause enumeration would still be possible regardless. Keys must be stored in memory, on-disk or via a secret server meaning column encryption would not mitigate the impact of RCE/full shell compromise. Add in the cost of column level encryption when querying large volumes of data, this seems to be entirely angled at gold plated compliance security theatre rather than solving any actual problem.
Thanks Dan, this is very interesting. From someone deeply involved in privacy I see the benefits of the auditability and risk mitigation in cases like SQL injection.
What does the risk profile look like in a full leak of the encrypted database?
If you had a column of integers are you able to order them without decrypting? Check that values are the same? Identify null values?