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Split a secret into N shares so any K of them can reconstruct it, and recover it later. Everything runs in your browser.
Each byte of the secret becomes the constant term of a random degree K-1 polynomial over GF(256). Shares are points on those polynomials; any K points recover the secret by Lagrange interpolation, while fewer reveal nothing. Each share line starts with its index byte.
Split a secret into N shares so any K reconstruct it, and recover it later. Runs entirely in your browser using GF(256).
Shamir's Secret Sharing, invented by Adi Shamir in 1979, splits a secret into several shares so that a chosen number of them are needed to rebuild it, while any fewer reveal nothing at all. It is used for backing up master keys, crypto wallet seeds and recovery codes across multiple people or locations. This tool splits a secret into N shares with a threshold K, and recovers the secret from any K of those shares.
Input:
secret + N=5, K=3
Output:
5 share strings; any 3 rebuild the secret
How many shares do I need to recover?
Exactly the threshold K you chose at split time, or more. Fewer than K reveal nothing about the secret.
Is this encryption?
It is information-theoretic secret splitting, not encryption with a password. The security comes from withholding shares, so distribute and store them separately.
What can the secret be?
Any UTF-8 text, such as a passphrase, key or seed phrase. Longer secrets simply produce longer shares.
Is anything uploaded?
No. Splitting and recovery run entirely in your browser, and random coefficients come from your browser's secure RNG.