A SLIP-0039 library for Go. Specifically, this library is a port of the SLIP-0039 python reference implementation to Go.

SLIP-0039 describes a standard and interoperable implementation of Shamir's secret sharing (SSS). SSS splits a secret into unique parts which can be distributed among participants, and requires a specified minimum number of parts to be supplied in order to reconstruct the original secret. Knowledge of fewer than the required number of parts does not leak information about the secret.

See https://github.com/satoshilabs/slips/blob/master/slip-0039.md for the full SLIP-0039 specification.

This implementation is not using any hardening techniques. Secrets are passed in the open, and calculations are most likely vulnerable to side-channel attacks. The code has not been audited by security professionals. Use at your own risk.

At the very least, you should not use this library for non-testing purposes or with sensitive secrets outside an air-gapped live system such as Tails.

No executables are provided with this library. You can write your own tools pretty simply, or I have a sister project called seedkit which provides a CLI that makes use of this library.

package main

import (
	"encoding/hex"
	"fmt"

	"github.com/gavincarr/go-slip39"
)

func main() {
	masterSecret := "bb54aac4b89dc868ba37d9cc21b2cece"
	passphrase := "TREZOR"

	// Generate a single group of 3 of 5 shares for masterSecret
	masterSecretBytes, _ := hex.DecodeString(masterSecret)
	groupCount := 1
	memberGroupParams := []slip39.MemberGroupParameters{{3, 5}}
	groups, _ := slip39.GenerateMnemonicsWithPassphrase(
		groupCount,
		memberGroupParams,
		masterSecretBytes,
		[]byte(passphrase),
	)
	fmt.Println(len(groups[0]))
	// Output: 5

	// Combine 3 of the 5 shares to recover the master secret
	shares := []string{groups[0][0], groups[0][2], groups[0][4]}
	recoveredSecret, _ := slip39.CombineMnemonicsWithPassphrase(
		shares,
		[]byte(passphrase),
	)
	fmt.Println(hex.EncodeToString(recoveredSecret))
	// Output: bb54aac4b89dc868ba37d9cc21b2cece
}