Seed Phrase Storage
Your 12 or 24-word crypto recovery phrase is the only thing standing between you and permanent loss of your funds. If someone gets it, they own your wallet. If you lose it, your crypto is gone forever. UnderKey stores seed phrases encrypted on your phone, offline and away from cloud backups, so they're accessible when you need them but never exposed to the internet.
How it works
- Create a secure note in UnderKey. Instead of storing a scan or photo, you type or paste your seed phrase as text.
- The text is encrypted with AES-256 using your unlock pattern, just like any other document in your vault.
- The note never touches your clipboard for longer than necessary. Once you paste the seed phrase into UnderKey and save it, clear your clipboard immediately to prevent other apps from reading it.
- The encrypted note is stored on your device, not in the cloud. It doesn't sync to iCloud, Google Drive, or any other service.
When you need to recover your wallet, unlock UnderKey, open the note, and copy the seed phrase. After you've used it, lock the app and the phrase is encrypted again.
Why store seed phrases offline?
Most crypto holders know not to screenshot their seed phrase or email it to themselves, but many still store it somewhere that's secretly online:
- Notes apps that sync to the cloud (Apple Notes with iCloud, Google Keep, Evernote, Notion). Even if the note is "locked," it's stored on someone else's server.
- Password managers (unless they're offline or zero-knowledge). Some password managers sync to their own servers, which means your seed phrase exists in encrypted form online. If the encryption is ever broken or the service is breached, your phrase could be exposed.
- Cloud storage (Google Drive, Dropbox). Even if the file is password-protected, it's still sitting on a server that could be hacked or subpoenaed.
Offline storage means your seed phrase exists only on your device, never on a remote server, and never accessible to anyone who doesn't physically have your phone and your unlock pattern.
Seed phrases + metal backups: why you need both
UnderKey is for convenient access when you need to recover a wallet or verify a phrase quickly. But it's not a replacement for a durable physical backup:
- If your phone is lost, stolen, or destroyed, your seed phrase is gone. UnderKey doesn't sync to the cloud, so there's no online copy to recover from.
- If you forget your unlock pattern, your vault is permanently locked. There's no password reset or recovery mechanism.
The best setup is:
- One metal backup (a steel plate designed for seed phrases) stored in a safe, safety deposit box, or other secure physical location. Metal backups survive fire, water, and corrosion.
- One encrypted digital copy in UnderKey for when you need to access the phrase quickly without retrieving the metal backup.
The metal backup is your primary, un durable copy. The digital copy is your convenient, always-accessible fallback. For a full comparison of storage methods, see our guide on where to store a seed phrase safely.
What not to do
- Don't store your seed phrase in your photo library or camera roll. Photos sync to iCloud Photos or Google Photos by default, which means your phrase ends up on Apple or Google's servers.
- Don't email it to yourself. Email is searchable, unencrypted, and often left logged in on multiple devices.
- Don't keep it in a cloud-synced note or document. Even if the note is locked or password-protected, it's still on a server.
- Don't split it across multiple insecure locations. Storing half in email and half in your camera roll doesn't make it twice as secure — it makes it twice as easy to lose.
Multiple wallets, one vault
If you hold crypto across multiple wallets (e.g., one hardware wallet, one hot wallet, one exchange recovery phrase), you can store all of them in UnderKey. Label each note clearly so you know which phrase belongs to which wallet.
Decoy vaults for seed phrases
If you're travelling with a seed phrase or crossing a border, you can use UnderKey's decoy vault feature to create a second vault with a different unlock pattern. Put a few harmless documents in the decoy vault, and if you're forced to unlock the app, you draw the decoy pattern instead of the real one.
Limits and trade-offs
- If you lose your phone, your digital seed phrase copy is gone. This is why you need a metal backup stored separately.
- If you forget your unlock pattern, the encrypted note is permanently inaccessible. Again, this is why the metal backup is your primary copy.
- Typing a seed phrase on your phone's keyboard can be risky. Some keyboard apps log what you type or upload it to the cloud for autocorrect and predictive text. Use a keyboard you trust, or disable cloud sync and predictive features when entering sensitive text.
For maximum security
- Use a metal backup as your primary storage. Keep it in a safe or safety deposit box.
- Store a digital copy in UnderKey for quick access when you need to verify the phrase or recover a wallet.
- Never upload your seed phrase to cloud storage, email, or any online service.
- Clear your clipboard after pasting a seed phrase into UnderKey so other apps can't read it.
- Use a decoy vault if you're travelling with the phrase and worried about coercion or border inspections.
Related features
- Offline AES-256 encryption — how seed phrases are encrypted
- Decoy vaults — protecting sensitive notes from coercion