How to secure user data in the database with Rails?

The problem with encrypting your database is that anything you encrypt cannot be used in a SQL query, and also, it still has to be decrypted before it can be used. This means that you need to place the decryption key in close proximity to the database, and in most cases, if someone can compromise your database, that means they have also compromised your decryption key at the same time. Thus the encryption step has bought you very little. With passwords, no decryption is necessary because it's actually a hash function. You're far better off making sure the database is never compromised in the first place.

Always assume that if a hacker can compromise any portion of your security, they can compromise all of it. Chain is only as strong as its weakest link and all that.

Credit card numbers and social security numbers (which fortunately you don't usually need to index on) are probably the most obvious exception to this, but if you have to ask this question, you've got no business storing those items in the first place. There's all kinds of legal trouble you can get into for messing that stuff up.

Credit card number, SSNs, etc should always be stored encrypted.

Passwords should always be stored encrypted, using a one-way hash. This means that when the user supplies a password, you can determine if it matches what you stored in the DB, but given only the encrypted representation in the DB, you cannot from that determine their password, short of brute force/dictionary attacks.

I find that in my app's, I like to add unencrypted_**** readers and writers to my class, to make dealing with the encrypted representation painless.

class User  # has db column encrypted_cc_number  def unencrypted_cc_number    WhateverEncryptionClassYouUse.decrypt(encrypted_cc_number)  end  def unencrypted_cc_number=(val)    self.encrypted_cc_number = WhateverEncryptionClassYouUse.encrypt(val)  endend

Using layered security mechanisms and strong cryptography is good practice if you are storing a large amount of sensitive data. It is required by the Payment Card Industry’s Data Security Standard (PCI DSS). I suggest that you read the following guideline document: https://www.pcisecuritystandards.org/pdfs/pci_fs_data_storage.pdf.

You should definitely not "assume that it will never be compromised"