About

A pure Swift implementation of Shamir's Secret Sharing scheme. SwiftySSS is a library that exposes an API to split secret data buffers into a number of different shares. With the possession of some or all of these shares, the original secret can be restored. You can see demo app in the example project below.

Based on SecretShare.swift

Example

How To Split

let message = Data([UInt8]("Hello World!".utf8))
let secret = try! Secret(data: message, threshold: 3, shares: 5)
let shares = try! secret.split()
        
shares.forEach { share in
    print(share.description)
}
//print
//1-8d736120eef1ca0b2b58971c
//2-1b46510ea3e09d828f9a217c
//3-de505c42223100e6d6aed241
//4-cb1f8a6d9544593ab4d53807
//5-0e0987211495c45eede1cb3a

How To Combine

let share1 = "1-8d736120eef1ca0b2b58971c"
let share2 = "2-1b46510ea3e09d828f9a217c"
let share3 = "3-de505c42223100e6d6aed241"
let share4 = "4-cb1f8a6d9544593ab4d53807"
let share5 = "5-0e0987211495c45eede1cb3a"

let sharesStings = [share1, share2, share3, share4, share5]
let sharesObjects = sharesStings.compactMap { try? Secret.Share(string: $0) }
let someShares = [Secret.Share](sharesObjects[1...3])

let secretData = try!  Secret.combine(shares: someShares)
let secret = String(data: secretData, encoding: .utf8)

print(secret)
//print
//Hello World!

How To Split With Custom Representation

let message = Data([UInt8]("Hello World!".utf8))
let secret = try! Secret(data: message, threshold: 3, shares: 5)
let shares = try! secret.split()

let customRepresentationClosure: ((UInt8, Data) -> String) = { (point, bytes) -> String in
    return "\(point)+\(Data(bytes).hexEncodedString())"
}        
shares.forEach { share in
    print(share.description(closure: customRepresentationClosure))
}
//print
//1+8d736120eef1ca0b2b58971c
//2+1b46510ea3e09d828f9a217c
//3+de505c42223100e6d6aed241
//4+cb1f8a6d9544593ab4d53807
//5+0e0987211495c45eede1cb3a

How To Combine Custom Representation

let share1 = "1+8d736120eef1ca0b2b58971c"
let share2 = "2+1b46510ea3e09d828f9a217c"
let share3 = "3+de505c42223100e6d6aed241"
let share4 = "4+cb1f8a6d9544593ab4d53807"
let share5 = "5+0e0987211495c45eede1cb3a"

let sharesStings = [share1, share2, share3, share4, share5]

let customRepresentationClosure: (Any) throws -> (point: UInt8, bytes: Data) = { (value) -> (point: UInt8, bytes: Data) in
    guard let stringValue = value as? String else {
        throw "Invalid String Representation"
    }
    let components = stringValue.components(separatedBy: "+")
    guard let pointComponent = components.first,
        let point = UInt8(pointComponent)  else {
        throw "Invalid String Representation"
    }
    guard let bytesComponent = components.last,
        let bytes = Data(hex: bytesComponent)  else {
        throw "Invalid String Representation"
    }
    return (point, bytes)
}

let sharesObjects = sharesStings.compactMap { try? Secret.Share(closure: customRepresentationClosure, value: $0) }
let someShares = [Secret.Share](sharesObjects[1...3])

let secretData = try!  Secret.combine(shares: someShares)
let secret = String(data: secretData, encoding: .utf8)

print(secret)
//print
//Hello World!

Installation

CocoaPods

pod 'SwiftySSS', '~> 0.1'

Contributing and License

Distributed under the MIT license. See LICENSE for more information.