How Castle Keeps Your Information Secure

by Tim

Castle relies on its users’ trust to function. We will do anything and everything we can to maintain and preserve that trust.

In that vein, here is our complete methodology concerning sensitive information. I’ll start with the information we store on our servers, then move on to the information we pass to our third party payments processor, Balanced. Finally, I’ll discuss how Castle uses Balanced to transfer payments.


For tenants, Castle stores the following information:

  • Name
  • Address
  • Cell phone number
  • Lease end date
  • Rent amount

For landlords, Castle stores some different information:

  • Name
  • Cell phone number
  • Email address
  • Password1

Notice what Castle doesn’t store: bank account information. When you enter the information we need to link your Castle account to your bank account, Castle doesn’t keep any of it. Instead, Castle passes it straight to Balanced using 256-bit SSL encryption.


For tenants, Castle passes the following information to Balanced:

  • Name
  • Bank routing number
  • Bank account number

For landlords, Castle passes a little more information to Balanced:

  • Name
  • Street address and ZIP code
  • Month and year of birth
  • Last four digits of SSN
  • Bank routing number
  • Bank account number

For landlords running their properties through a business with an EIN, Castle passes a few more details to Balanced:

  • Business name
  • Business street address
  • Business phone number
  • EIN (Employer Identification Number)

The most sensitive information—the routing and account numbers—never touches Castle’s servers2. It all moves directly to Balanced, who protects that information with bank-level security. (Specifically, Balanced is PCI compliant.) Castle displays the image below during signup when the requested information is headed to Balanced:

Balanced powers payments for lots of great companies. Notable clients include Soylent, GroupMe, Artsy, and redditgifts.

Castle + Balanced

Castle deals with Balanced in two ways: linking bank accounts when users sign up, and transferring money when users make payments.

The process for linking bank accounts is a little technical, and Balanced does an admirable job explaining the steps. Here’s the jist:

  1. Castle passes a new user’s most sensitive information to Balanced, without storing any of it on Castle servers.
  2. Balanced stores the information on its secure servers, then creates a “funding instrument” that Castle can use to request transfers.
  3. Balanced passes Castle a link to the funding instrument. The link is unique to Castle and requires authentication from Castle for any request.

Once tenants verify their accounts with microdeposits, they can initiate payments through Castle. The process for transferring money is as follows:

  1. The tenant manually initiates a payment, or Castle initiates a payment if the tenant has activated automatic payments.
  2. Using the link to the funding instrument, Castle makes an authenticated request to Balance to transfer funds.
  3. Balanced transfers the funds into an escrow account, then transfers the funds to the destination account.

Your most sensitive information stays out of Castle’s servers, and your money stays out of Castle’s bank account.

If you have any other questions, especially if you’re a beta user, please use the Support page to contact us by email, phone, or live chat.

  1. Actually, it’s a hash of the password. When a landlord logs in, Castle hashes the submitted password and checks for a match to the stored hash. Only the landlord knows the password.
  2. The last four SSN digits and the EIN do touch Castle’s servers, but are never stored there.