Introducing BitKey Wallet

  • BitKey
  • 8 Minutes
  • June 1, 2018

Keyword: BitKey Wallet, NFC card, Innovative Features, Design principles

1. Introduction.

Bitkey is a simple Bitcoin wallet and focus on private key security. With BitKey you can manage your Bitcoin private keys within your own control. In 2014, BitKey 1.0 was released on appstore.

After about four years, BitKey wallet will introduce a new exciting feature, with some hardware accessories.

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Figure: BitKey is ready scanning NFC-XOR-KEY card to sign a transaction.

The hardware accessory is a NFC device, we call it NFC-XOR-KEY card. This card plays a key role to protect private keys which will be described in detail.

For end user of Bitcoin, private key is the most important thing and must never be revealed to others[0]. Managing, controlling, storing private keys are complex tasks, and no easy solution has been proposed[1]. The new introduced feature is directly focus on key security, and I believe the innovated NFC-XOR-KEY card will be the best practice to keep private key safe, especially on mobile platform.

2. BitKey`s principles.

I believe data loss is more a disaster than have been stolen. If you lost the private key meant that you lost your digital assets forever, no one can get these coins back. So Bitkey keeps a version controlling of any change of your data, locally and remotely, which backup your data properly. The built-in logic is that the data version will only go forward and cannot be overwritten, deleted, or reverted. When you use a new phone or careless delete your app, even delete your cloud data, the latest version of data should can be recovery. (However, please never try to delete the wallet app and cloud data)

The wallet data is encrypted by user password with industry-standard cryptography algorithms. So user should set a strong password to encrypt your data. And write a good hind to help you remember the password. The password does not have saved ANYWHERE, if you do not remember it, no one can decrypt the data for you.

Besides these standard encrypt measures, we innovative use XOR key to enhance data security in two ways: First, to enhance the security of cloud storage with segmentation data. Second, at the inner layer, the NFC-XOR-KEY encrypt the private key data to provide perfect security, this is very important in the circumstance of cloud data backup. (Perfect security[3]).

Bitkey does not store your data in a central server, but only put the latest version data in your own iPhone’s sandbox. Even the encrypted data backup on your iCloud is also isolation. Bitkey has no built-in function to collect and statistic user information. Bitkey have no owner server directly communicate with the app. Also, Bitkey does not want to know any of this information too, there is no good for both sides.

Every history binary version is kept on appstore, this can provide a trusted third party backup for auditing.

You can subscribe the app’s latest code, and review, to know the build-in workflow.

Bitkey has a built-in Network proxy, with this you can review all the network request send from the app.

3. BitKey`s design style

Bitkey is a simple Bitcoin wallet focus on private key management, it is much more like a key management tool. It`s user experience may differs from other wallets, for example we want to demonstrate Bitcoin’s internal working mechanisms, such as the transaction signing and the transaction broadcast process. We believe explicit processes can help users understand the Bitcoin technology and the clear working flow is also an important user experience. Many of our users like BitKey‘s work style.

With BitKey you can actual sign a transaction and Broadcast the raw tx data to Bitcoin network. And, there is transaction data logs, you can review the transaction content, which you signed.

4. Innovative feature

The above paragraphs have mentioned the NFC device NFC-XOR-KEY card. Here, I will briefly introduce how it works and the great benefits it brings. With a NFC-XOR-KEY card the app works as a hybrid wallet, these combines the advancement of hardware wallet and software wallet, with good usability and height security.

BitKey use NFC-XOR-KEY to encrypt the private-key inner layer. XOR here is Exclusive-OR cipher. The encrypted (XORed) private-key has characters of Perfect Secrecy [4].

The NFC-XOR-KEY card can be used many times to protect number of private keys, this means we can use classic address (according HD address) again, and keep bag of independent private-keys. (Recently, this classic type address has been replaced in a lot of wallets with HD format addresses, but this classic format still has many advantages, it is independence, more security, and may have a big role to resist quantum threat. )

Most important, with the inner XOR cipher protection, even if an attacker gets all your wallet data and brutally cracks your user-password-encrypted wallet data, they still can’t get the private keys. Even with a huge brutally force, the XORed private keys cannot possible be cracked. So this makes using an open cloud storage to backup wallet data is more practicable.

Because the inevitable user’s weak password, the wallet data protected by advanced encryption algorithm (like AES) backup in cloud is still in extremely risky by being brute-force cracked. With the innovative XOR card solution, you don’t have to worry about such brute-force attack.

For more information about XOR passwords and NFC-XOR-KEY methods, you can continue reading other blogs.

5. References

[1] Bitcoin official website, Some Bitcoin words you should familar. bitcoin.org
[2] Shayan Eskandari, Jeremy Clark, David Barrera, Elizabeth Stobert. A first look at the usability of bitcoin key management.arxiv
[3] Information theoretic security.wikipedia
[4] XOR cipher. wikipedia
[5] One-time pad. wikipedia