Build Your Own Data Privacy Vault

This challenge is to build your own Data Privacy Vault. A Data Privacy Vault is a way to keep sensitive information safe. The vault stores the data and controls who can get to it, making sure it's managed, watched over, and used carefully.

Every business has sensitive data, whether it's about people's health (medical records), their payment details (credit card numbers), or other personal information (names and addresses).

At the same time every business wants and needs to leverage that data: analysing trends, processing payments, confirming someone's identity or simply delivering the product to the customer. The data is incredibly valuable so keeping it safe and secure is essential to the ongoing operation of a business as well as compliance with industry and legally required standards.

A data vault helps businesses achieve this by separating sensitive data and storing it in a secure service or ‘vault’. This vault then controls access to the data only when absolutely needed.

The Challenge - Building Your Own Data Privacy Vault

For this challenge we’re going to build a service that can function as a Data Privacy Vault, that’s the green bit in the high-level diagram below that conceptually shows where it would fit in some sort of production system.

Our service will provide a HTTP based API that can be used to send sensitive data to be stored in the vault, receiving back a token that can later be used to retrieve the sensitive data by an authorised user/service.

To understand why the Data Privacy Vault is preferable to just encrypting the data check out Wikipedia’s article on Tokenization.

Step Zero

In all the best programming languages we index arrays from zero. Coding Challenges continues that trend starting every challenge from step zero.

As usual, step zero is to set up your IDE / editor of choice and programming language of choice. We’re going to build a service with HTTP based API so pick your favourite language to do that with or the one you most fancy learning.

Aside: Some programming language index arrays from zero because arrays are essentially a pointer to the beginning of a contiguous block of memory and an offset from that point. In other words, if you’re familiar with C then array[index] is equivalent to *(array + index).

Step 1

In this step your goal is to create a simple tokenisation service that can create tokens and return their value, for the moment storing the data in memory is fine.

Once this is done you should have two endpoints:

Endpoint: /tokenize

Method: POST

Request payload:

{
	"id": req-12345”,
	"data": {
		"field1": "value1",
		"field2": "value2",
		"fieldn": "valuen"
	}
}

Success response: HTTP Code 201

Payload:

{
	"id": req-12345”,
	"data": {
		"field1": "t6yh4f6",
		"field2": "gh67ned",
		"fieldn": "bnj7ytb"
	}
}

Don’t forget to create the appropriate error response codes.

Endpoint: /detokenize

Method: POST

Request payload:

{
	"id": req-33445”,
	"data": {
		"field1": "t6yh4f6",
		"field2": "gh67ned",
		"field3": "invalid token"
	}
}

Response:

	"id": req-33445”,
	"data": {
		"field1": {
			"found": true,
			"value": "value1"
		},
		"field2": {
			"found": true,
			"value": "value2"
		},
		"fieldn": {
			"found": false,
			"value": ""
		}
	}

Don’t forget to create the appropriate error response codes and to handle a token not being found.

Step 2

In this step your goal is to store the data in a persistent store. All data should be stored encrypted. You could use something like Redis for this (and you could even build your own Redis). Be sure to pick an encryption algorithm that is suitably secure for privacy related data.

For some services the use of a format-preserving encryption algorithm will make it easier to drop a Privacy Data Vault into an existing solution. As the name suggests, this type of encryption keeps the format (and length) of the data. For example, consider a phone number, if the original number is +44 7974 314 455, then the encrypted data would retain the format but the value, will change to something like: +12 4325 465 432.

Step 3

In this step your goal is to support authenticated access to the data in the vault. Think about service to service authentication and that the reader might not be the same as the writer.

Add some support for verifying that the caller is allowed to create tokens and refusing requests to create them without the correct permissions.

Add support for verifying that the caller is allowed to detokenize, returning a suitable error if they are not.

N.B. Don’t forget that when deployed to production communication with the Privacy Data Vault should be using HTTPS.

Going Further

This is been an introduction to Data Privacy Vaults. To build out a more complete solution you can:

• Allow a format to be specified for the data payload(s) to be tokenized.
• Extend the authentication to integrate with common identify and access management solutions.
• Integrate with a key management system to keep the cryptographic keys secure.
• Provide alternative ways of calling the service, perhaps websockets or gRPC.
• Creating a deployable service.
• Turn it into a business - for example there are several Data Privacy Vaults available as commercial products in the AWS marketplace.

Help Others by Sharing Your Solutions!

If you think your solution is an example other developers can learn from please share it, put it on GitHub, GitLab or elsewhere. Then let me know - ping me a message on the Discord Server, via Twitter or LinkedIn or just post about it there and tag me. Alternately please add a link to it in the Coding Challenges Shared Solutions Github repo.

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