Documentation
¶
Overview ¶
Package secretsharing provides methods to split secrets into shares.
Let n be the number of parties, and t the number of corrupted parties such that 0 <= t < n. A (t,n) secret sharing allows to split a secret into n shares, such that the secret can be recovered from any subset of at least t+1 different shares.
A Shamir secret sharing [1] relies on Lagrange polynomial interpolation. A Feldman secret sharing [2] extends Shamir's by committing the secret, which allows to verify that a share is part of the committed secret.
New returns a SecretSharing compatible with Shamir secret sharing. The SecretSharing can be verifiable (compatible with Feldman secret sharing) using the CommitSecret and Verify functions.
In this implementation, secret sharing is defined over the scalar field of a prime order group.
References
[1] Shamir, How to share a secret. https://dl.acm.org/doi/10.1145/359168.359176/ [2] Feldman, A practical scheme for non-interactive verifiable secret sharing. https://ieeexplore.ieee.org/document/4568297/
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Recover ¶
Recover returns a secret provided more than t different shares are given. Returns an error if the number of shares is not above the threshold t. Panics if some shares are duplicated, i.e., shares must have different IDs.
func Verify ¶
func Verify(t uint, s Share, c SecretCommitment) bool
Verify returns true if the share s was produced by sharing a secret with threshold t and commitment of the secret c.
Example ¶
package main
import (
"crypto/rand"
"fmt"
"github.com/cloudflare/circl/group"
"github.com/cloudflare/circl/secretsharing"
)
func main() {
g := group.P256
t := uint(2)
n := uint(5)
secret := g.RandomScalar(rand.Reader)
ss := secretsharing.New(rand.Reader, t, secret)
shares := ss.Share(n)
coms := ss.CommitSecret()
for i := range shares {
ok := secretsharing.Verify(t, shares[i], coms)
fmt.Printf("Share %v is valid: %v\n", i, ok)
}
got, err := secretsharing.Recover(t, shares)
fmt.Printf("Recover secret: %v\nError: %v\n", secret.IsEqual(got), err)
}
Output: Share 0 is valid: true Share 1 is valid: true Share 2 is valid: true Share 3 is valid: true Share 4 is valid: true Recover secret: true Error: <nil>
Types ¶
type SecretCommitment ¶
SecretCommitment is the set of commitments generated by splitting a secret.
type SecretSharing ¶
type SecretSharing struct {
// contains filtered or unexported fields
}
SecretSharing provides a (t,n) Shamir's secret sharing. It allows splitting a secret into n shares, such that the secret can be only recovered from any subset of t+1 shares.
Example ¶
package main
import (
"crypto/rand"
"fmt"
"github.com/cloudflare/circl/group"
"github.com/cloudflare/circl/secretsharing"
)
func main() {
g := group.P256
t := uint(2)
n := uint(5)
secret := g.RandomScalar(rand.Reader)
ss := secretsharing.New(rand.Reader, t, secret)
shares := ss.Share(n)
got, err := secretsharing.Recover(t, shares[:t])
fmt.Printf("Recover secret: %v\nError: %v\n", secret.IsEqual(got), err)
got, err = secretsharing.Recover(t, shares[:t+1])
fmt.Printf("Recover secret: %v\nError: %v\n", secret.IsEqual(got), err)
}
Output: Recover secret: false Error: secretsharing: number of shares (n=2) must be above the threshold (t=2) Recover secret: true Error: <nil>
func New ¶
New returns a SecretSharing providing a (t,n) Shamir's secret sharing. It allows splitting a secret into n shares, such that the secret is only recovered from any subset of at least t+1 shares.
func (SecretSharing) CommitSecret ¶
func (ss SecretSharing) CommitSecret() SecretCommitment
CommitSecret creates a commitment to the secret for further verifying shares.
func (SecretSharing) Share ¶
func (ss SecretSharing) Share(n uint) []Share
Share creates n shares with an ID monotonically increasing from 1 to n.
func (SecretSharing) ShareWithID ¶
func (ss SecretSharing) ShareWithID(id group.Scalar) Share
ShareWithID creates one share of the secret using the ID as identifier. Notice that shares with the same ID are considered equal. Panics, if the ID is zero.
Source Files