Smart Cryptography with Superdog and Vault

Superdog - the Crypto library for Vault from Hashicorp

At XOR Data Exchange we deal with a lot of sensitive data for our customers. We needed to be able to support strong encryption with key rotation in a simple and practical way. So we wrote superdog to help with this task. Superdog is a library for managing strong cryptography in both development/test environments. Superdog provides an elegant wrapper to the Vault API that allows you to manage your cryptographic keys using any code that implements the KeyProvider interface. An implemention of the KeyProvider interface is provided for Vault, but others could be supported.

Using Vault allows us to have secure and strong separation between the keys and the encrypted text. Superdog takes that separation a step further by allowing us to use our encryption routines in our Development/Test/Staging environments without worrying about having an instance of Vault available. We provide this abstraction using a KeyProvider interface. By default, the DevKeyProvider is used. DevKeyProvider is an insecure provider that always uses the same keys and initialization vectors. It should never ever be used in Production.


  • Versioned Keys - Key version is stored as the first few bytes of the encrypted text
  • Key Rotation - Rotate your keys safely, knowing that you’ll always be able to decrypt older versionss
  • Development implementation for tests and local development
  • Versioned and Rotated IV/Salt - SaltProvider interface works the same as KeyProvider to allow development and testing access to the crypto libraries without requiring a live Key (Vault) server
  • Reencrypt function to simplify key rotation, decrypts with given key, reencrypts with latest key

Cypher Suites

superdog supports AES encryption with CFB/CTR/GCM/OFB modes.


On Go version 1.5.2 / Linux x86_64 kernel 4.2.5 on a quad-core i7:

BenchmarkKeyEncryptCFB-8	 1000000	      2024 ns/op
BenchmarkKeyEncryptCTR-8	  500000	      2748 ns/op
BenchmarkKeyEncryptGCM-8	 1000000	      2381 ns/op
BenchmarkKeyEncryptOFB-8	  500000	      2665 ns/op
BenchmarkKeyDecryptCFB-8	10000000	       215 ns/op
BenchmarkKeyDecryptCTR-8	 2000000	       898 ns/op
BenchmarkKeyDecryptGCM-8	 3000000	       520 ns/op
BenchmarkKeyDecryptOFB-8	 2000000	       817 ns/op


go get -u


val := []byte("encrypt me!")

// use a key prefix to delineate different crypto keys
// allowing you to use different keys for different parts of your application
// or different fields of a database table, for example
b, err := superdog.Encrypt("mykeyprefix", val, val)
if err != nil {
	// handle error


b := []byte("some crypt cypher text here")
decrypted, err := superdog.Decrypt([]byte("mykeyprefix"), b, b)
if err != nil {
	// handle error

Production Usage

By default, superdog uses the DevKeyProvider which is a static key with static IV. This is extremely insecure, and SHOULD NOT ever be used in production.

We recommend using Go’s build tags to enable strong cryptography in production usage.

Create a file with your connection routines in the init() function. Add the build tag // +build production to the top of that file. Here’s an incomplete example:

// +build production

package main
import (

// Assign each application a unique UUID
// and use Vault's AppID authentication mechanism
const (

func init() {
	user := os.Getenv("VAULT_USER")
	vaultaddr := os.Getenv("VAULT_ADDRESS")
	// TEST these for empty strings & handle appropriately in your code

	cfg := api.DefaultConfig()
	cfg.Address = vaultaddr

	vault, err := hashi.NewVault(cfg)
	if err != nil {
		// handle appropriately
	err = vault.AuthAppID(appid, user)
	if err != nil {
		// handle appropriately

	crypto.DefaultKeyProvider = vault
	crypto.DefaultSaltProvider = vault


Now compile your program with go build -tags production to include this code. The KeyProvider will be set to use Vault.

Contributions Welcome

We hope you enjoy using Superdog, and we’re always excited to accept contributions from the community. Superdog helps us support our mission of providing safe and secure access to data using responsible security measures. The original implementation of Superdog was written by Erik St. Martin.

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