Frequently Asked Questions

How do I install kr on my computer?
curl | sh

Or install from source:
For more ways to install kr, visit
I keep my private key in ~/.ssh, why should I use Kryptonite?
Any application you run can read, use, and send off your private key without your knowledge. Kryptonite requires your explicit permission to use the private key and records every SSH access.
I have two-factor authentication enabled on my GitHub account. Why should I use Kryptonite?
GitHub does not enforce two-factor authentication when you push or pull code with SSH. Using Kryptonite requires access to your phone to use the SSH key.
Does have access to my SSH private key?
No, the SSH private key is generated on the mobile device and never leaves. Furthermore, there are no trusted third-parties and all of the Kryptonite source code is published to the public. See more.
Where can I inspect the Kryptonite source code?
The Kryptonite source code for kr, kryptonite-ios, and kryptonite-android is published at Feel free to compile Kryptonite from source and run it on your phone and workstation.
How is the SSH private key stored on my phone?

On iOS, Kryptonite generates a 4096-bit RSA key pair using the Apple iOS Security framework or optionally an Ed25519 key pair using libsodium. Kryptonite stores the private key in the iOS Keychain with accessibility level “kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly”. To learn more about the security of Apple cryptography libaries and the Apple iOS Keychain see:

On Android, Kryptonite generates a 3072-bit RSA key pair (because of the long secure hardware key generation time). The private key is stored in secure hardware called the Android Keystore and cannot be extracted, even by Kryptonite. The Android Keystore performs private key operations as a black box.

If the SSH private key never leaves my phone, how does it work?
The role of a private key in an SSH login is to sign the SSH handshake. When a signature is required, your workstation calls out to Kryptonite running on the paired phone with the data that must be signed. If authorized, Kryptonite performs the signature using the private key and returns only the signature to the workstation.
What happens if I lose my phone?
First make sure you remove the old SSH public key from any of your accounts. Once you have Kryptonite installed on your new phone, add the new public key to the accounts you were using SSH with before.
How does Kryptonite affect my SSH client?
Upon install, Kryptonite adds a few lines to your SSH configuration (at ~/.ssh/config) that cause SSH to offer your Kryptonite key. Your other keys will still be presented and your Kryptonite key will only be used if it has access to the service you are connecting to.
How does my phone communicate with my computer securely?
Your phone generates a session key pair and encrypts the public key to your workstation upon pairing. All communication is encrypted and authenticated using session key pairs.
Can I backup my private key?
Backing up your private key reduces its security to the security of the backup. We do not currently support backing up or extracting your private key. In the future we may add key splitting among team members or transferring your private key directly to a new phone.

Have more questions?