A Smart Key is a single key that provides access to all of your wallets. The Smart Key is always held by the user and is protected by a backup key that can be written down and stored as a paper wallet. Aside from your paper copy, your Smart Key is stored in the cryptographic section of your phone and protected by: your phone's lockscreen pin/passphrase; your Universal Wallet pin; and optionally another layer of biometric authentication.
Your smart key will never touch the internet and is not stored by Ethos. Ethos cannot authorize or spend any of your funds without your Smart Key. Your Smart Key is tied to your password and your backup key so that you always have secure access to your funds wherever you go.
The Smart Keys are built by combining the best of the BIP32, BIP39, and BIP44. A single 256-bit "root" key can be used to derive any coin that supports these standards. In addition, Smart Keys enable multiple account types spanning individual, joint and custodial - all from the root key.
How is my Smart Key created?
When you first create your wallet, you will be instructed to shake your device to generate your Smart Key. This is done 4 times, each time generating 6 words and never displaying them all at once on the screen.
When creating your Smart Key, your device does not need to be connected to the internet for the SmartKey generation. After that process, you will need your device conntected to the internet in order to complete a handshake with Ethos servers so we can associate your extended public key - that is derived from your SmartKey - to your Ethos account. This helps ensure no one else can use your SmartKey on a different Ethos account. It is up to you to save your Smart Key somewhere safe. Ethos does not maintain a copy and this is for your protection, ensuring that you, and you alone, can restore your wallet if needed.
Adhering to the BIP39 standard, your Smart Key will be a 24-word phrase that is randomly generated from a list of 2048 words. We are using multiple sources of entropy (random data) to generate Smart Keys- one of which is the accelerometer data! These help us ensure the Smart Key that is generated is truly random.
Can someone else guess or generate my Smart Key?
The probability of this is astronomically low. If the words selected for our 24-word phrase are chosen from a list of 2048 words, there are 2048^24 combinations. This can also be written as 2.96*10^79, or 29,642,774,844,752,946,028,434,172,162,224,104,410,437,116,074,403,984,394,101,141,506,025,761,187,823,616, combinations! That's more than 1 billion keys for every atom on Earth.