4 ms·

Ask HN: Is there a safe way to encrypt databases?

Dear HN, Is there a safe way to encrypt databases? My understanding of the issue is that if it is encrypted, then the key has to exist on the same machine anyway, so there's not much point.

davidw 15y ago
You could use the user's password, when they log in?
- alexchamberlain 15y ago
  What if they lose their password? The password has to be hashed in the database, so there is no way to decrypt the data. Furthermore, it introduces problems for sharing between users.
  - mike-cardwell 15y ago
    Generate a key for each user. Encrypt the users key with their password, but then create a second backup encrypted copy using public key crypto. If the user loses their password, then you can have systems in place to retrieve the key from the backup encrypted container. The process of retrieving the key could involve somebody manually approving the decryption of it on a secondary system where the private key lives, and then copying it over to the original server to be re-encrypted with the users new password. EDIT: If data needs to be shared between users, then a new sharing key can be created, and encrypted with both users passwords and the backup public key. That data can then be re-encrypted with the shared key.
    - davidw 15y ago
      It's nice to read this, because I have recently been involved in creating just such a system, and it's pretty close to how you describe it.
      - mike-cardwell 15y ago
        I'd be interested to read about such a system if you ever have the motivation and opportunity.
traxtech 15y ago
There's a point, because if your sysadmin is competent, having access to the database of a webapp (webapp break-in) is much easier than being able to dump the server memory (OS break-in). You can go hardware with a cryptographic accelerator PCI card (good luck integrating that in your webapp)
Firehed 15y ago
What data are you trying to protect? There are a number of different approaches to this, all of which vary by what you're trying to achieve. You can encrypt certain fields generating an encryption key based on non-encrypted data in the row (ex. your key may be sha256(primary key value + create time + application secret), and rather than protecting one master key you must protect the key-generation algorithm). Or you can have one master key that you use to encrypt data - this key should never be written to disk (the key should be decrypted into memory from your key custodians' passwords). Or a combination of both. You should also have a way to version keys so that you can perform key rotation. Certain DB engines allow the entire database file to be encrypted (SQLite offers this with some paid extension, I believe). Or have the user encrypt the data before sending it (as some backup services do). Consult an expert. I could give more details about effective encryption strategies, but I don't want a newbie finding my post, reading half of it, and implementing something dangerously bad. At least no encryption is at a known level of safety; data that's been encrypted incorrectly gives a huge false sense of security.

Dear HN, Is there a safe way to encrypt databases? My understanding of the issue is that if it is encrypted, then the key has to exist on the same machine anyway, so there's not much point.

davidw 15y ago

You could use the user's password, when they log in?

alexchamberlain 15y ago
What if they lose their password? The password has to be hashed in the database, so there is no way to decrypt the data. Furthermore, it introduces problems for sharing between users.
- mike-cardwell 15y ago
  Generate a key for each user. Encrypt the users key with their password, but then create a second backup encrypted copy using public key crypto. If the user loses their password, then you can have systems in place to retrieve the key from the backup encrypted container. The process of retrieving the key could involve somebody manually approving the decryption of it on a secondary system where the private key lives, and then copying it over to the original server to be re-encrypted with the users new password. EDIT: If data needs to be shared between users, then a new sharing key can be created, and encrypted with both users passwords and the backup public key. That data can then be re-encrypted with the shared key.
  - davidw 15y ago
    It's nice to read this, because I have recently been involved in creating just such a system, and it's pretty close to how you describe it.
    - mike-cardwell 15y ago
      I'd be interested to read about such a system if you ever have the motivation and opportunity.

traxtech 15y ago

There's a point, because if your sysadmin is competent, having access to the database of a webapp (webapp break-in) is much easier than being able to dump the server memory (OS break-in). You can go hardware with a cryptographic accelerator PCI card (good luck integrating that in your webapp)

Firehed 15y ago

What data are you trying to protect? There are a number of different approaches to this, all of which vary by what you're trying to achieve. You can encrypt certain fields generating an encryption key based on non-encrypted data in the row (ex. your key may be sha256(primary key value + create time + application secret), and rather than protecting one master key you must protect the key-generation algorithm). Or you can have one master key that you use to encrypt data - this key should never be written to disk (the key should be decrypted into memory from your key custodians' passwords). Or a combination of both. You should also have a way to version keys so that you can perform key rotation. Certain DB engines allow the entire database file to be encrypted (SQLite offers this with some paid extension, I believe). Or have the user encrypt the data before sending it (as some backup services do). Consult an expert. I could give more details about effective encryption strategies, but I don't want a newbie finding my post, reading half of it, and implementing something dangerously bad. At least no encryption is at a known level of safety; data that's been encrypted incorrectly gives a huge false sense of security.