Shamir Backup

Shamir backup is a method of splitting a wallet seed into multiple shares such that a chosen threshold, for example any 3 of 5, can reconstruct the secret, while fewer shares reveal nothing at all. It applies Shamir's secret sharing, published by cryptographer Adi Shamir in 1979, to bitcoin key material, standardized for wallets as SLIP 39.

Why it matters

A single seed phrase is a single point of failure twice over: anyone who finds it can take everything, and if it burns or is lost, everything is gone. Shamir backup addresses both risks at once. Shares stored in separate locations mean a burglar finding one learns nothing, while the holder can still lose one or two shares to fire or misplacement and recover fully. This makes it a practical foundation for inheritance and disaster planning without trusting any single location, person, or company.

How it works

The scheme encodes the secret as a point on a random polynomial and hands out other points on the curve as shares; any threshold number of points determines the polynomial exactly, while fewer leave it mathematically undetermined. In wallet practice each share is itself a word list, generated and later recombined inside a hardware device so the full secret never touches an internet-connected computer. It differs from multisig, which splits signing authority across independent keys rather than splitting one secret, and the approaches suit different threat models.