Shamir's Secret Sharing
A cryptographic method for splitting a secret, such as a wallet seed, into multiple shares so that only a minimum threshold of them can reconstruct the original.
Shamir's Secret Sharing is a cryptographic scheme that splits a secret — most commonly a wallet's seed phrase (see Kaavon's "Seed Phrase" glossary definition) — into a set number of shares, such that any threshold number of those shares (for example, three out of five) can mathematically reconstruct the original secret, while any smaller number reveals no usable information about it at all. This is distinct from simply cutting a seed phrase into pieces, since each individual share on its own is cryptographically meaningless.
The scheme is commonly used for wallet backup and social recovery (see Kaavon's "Social Recovery Wallet" glossary definition), letting a user distribute shares among trusted people or secure locations so that losing any single share doesn't lose the wallet, while an attacker who obtains fewer than the threshold number of shares gains nothing. The tradeoff is added complexity in managing and securely distributing multiple shares compared to a single seed phrase, and the need to ensure enough shares remain recoverable if the user needs to reconstruct the secret later.
Examples
- A user might split their seed phrase into five Shamir shares distributed across trusted family members, requiring any three to reconstruct it if the wallet needs to be recovered.
- Unlike simply photocopying and splitting a seed phrase into fragments, a genuine Shamir's Secret Sharing share reveals no information about the original secret below the reconstruction threshold.