SLIP39 Shamir Backup Recovery: Combining Your Shares

If your Trezor backup is several lists of 20 (or 33) words rather than a single 12- or 24-word phrase, you have a SLIP39 Shamir backup. It's a different — and rather clever — standard, and recovering it means combining your shares.

Paste your shares (one per line) into the Validate tool — it combines them in your browser and never sends anything anywhere.

What Shamir backup actually does

A normal seed phrase is a single secret: lose it and you're locked out; let someone copy it and they own your coins. SLIP39 splits that secret into multiple shares using Shamir's Secret Sharing, with a threshold:

• 2-of-3: any two of three shares recover the wallet; any single share is useless.
• It can even be two-level — several groups, each needing a threshold of member shares, with a threshold of groups required overall.

This lets you survive losing a share, and resist a single share being stolen. The math guarantees that below the threshold, the shares reveal nothing.

Why it isn't BIP39

• Its own wordlist — 1024 words (BIP39 has 2048), so the words differ.
• Share length — 20 words for a 128-bit secret, 33 words for 256-bit.
• A different checksum (RS1024) and a layered secret-sharing structure.

So a SLIP39 share won't import into a BIP39 wallet, and our BIP39 validator will tell you it isn't BIP39 — because it's Shamir.

How to recover

1. Gather at least the threshold number of shares (and from enough groups, if your backup uses groups).
2. Open the Validate tab and paste each share on its own line.
3. The tool reads the scheme, tells you how many more shares it needs, and — once you have enough — combines them to recover the master secret and shows the wallet's addresses.
4. If you used a SLIP39 passphrase, you'll need it too (a different passphrase yields a different, hidden wallet — much like BIP39).

To actually spend, restore the recovered backup in a compatible wallet (e.g. a Trezor, or any SLIP39-aware tool).

If you're short a share

If you don't have the threshold, the wallet genuinely cannot be recovered yet — that's the security model working as intended. Track down another share; you do not need all of them, just the threshold. No tool or service can shortcut this, and anyone claiming otherwise is a scam.

Stay safe

• Combine shares offline when you can; the tool needs no connection.
• Never share your shares or paste them into a site that transmits them — see is it safe to enter your seed phrase online.
• After recovering on an online device, move funds to a fresh wallet.

Shamir backup trades one fragile secret for several resilient ones. Collect your threshold, combine, confirm the address, and you're back in. New to seeds? Start with what is a seed phrase.

Combine your SLIP39 shares →