com.codahale.shamir

Class Scheme

java.lang.Object

com.codahale.shamir.Scheme

public class Scheme
extends Object

Scheme implemented Shamir's Secret Sharing over GF(256) to securely split secrets into N parts, of which any K can be joined to recover the original secret.

Scheme uses the same GF(256) field polynomial as the Advanced Encryption Standard (AES): 0x11b, or x^8 + x^4 + x^3 + x + 1.

See Also:

Shamir's Secret Sharing, The Finite Field {@code GF(256)}

Constructor Summary

Constructors

Constructor and Description
Scheme(int n, int k) Creates a new Scheme instance.

Method Summary

Modifier and Type	Method and Description
okio.ByteString	join(Set<Part> parts) Joins the given parts to recover the original secret.
Set<Part>	split(okio.ByteString secret) Splits the given secret into n parts, of which any k or more can be combined to recover the original secret.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Scheme

public Scheme(int n,
              int k)

Creates a new Scheme instance.

Parameters:

n - the number of parts to produce (must be >1)

k - the threshold of joinable parts (must be <= n)

Method Detail

split

public Set<Part> split(okio.ByteString secret)

Splits the given secret into n parts, of which any k or more can be combined to recover the original secret.

Parameters:

secret - the secret to split

Returns:

a set of n Part instances

join

public okio.ByteString join(Set<Part> parts)

Joins the given parts to recover the original secret.

N.B.: There is no way to determine whether or not the returned value is actually the original secret. If the parts are incorrect, or are under the threshold value used to split the secret, a random value will be returned.

Parameters:

parts - a set of Part instances

Returns:

the original secret

Throws:

IllegalArgumentException - if parts is empty or contains values of varying lengths