Salut

The Salut protocol is a Swift 4 protocol for encrypted data transfer via Bonjour. It uses symmetric encryption and md5 hashing to transfer data.

Installation

Salut requires CryptoSwift. View their installation instructions first.

To install Salut, simply drop the source files from src into your XCode app.

Usage

Getting a peer ID

Getting a MCPeerID is easy. On iOS simply use:

let id = MCPeerID(displayName: UIDevice.current.name)

On macOS you have to use:

let id = MCPeerID(displayName: Host.current().name ?? "Mac")

Getting a password

Your password needs to be 32 alphanumeric symbols long. To generate a 32 symbols long md5 hash just use:

let code = "myPasswordOfVariableLength".md5()

Note that the md5 extension is part of CryptoSwift.

Setting up a Salut Server

Before you start, you have to run the server on the device you want to connect to.

let server = SalutServer(peerId: id), password: code)
server.prepare()
server.delegate = self

To react to specific server events, simply implement the SalutServerDelegate protocol. Here is an example with AppDelegate as the host class:

extension AppDelegate: SalutServerDelegate {
    func server(_ server: SalutServer, receivedSearchRequest package: Package) {
        print("Received search request.")
    }
    
    func server(_ server: SalutServer, sentSearchResponse package: Package) {
        print("Sent search response.")
    }
    
    func server(_ server: SalutServer, receivedDataTransmission package: Package) {
        print("Received data transmission.")
    }
    
    func server(_ server: SalutServer, receivedDecryptedTransmission data: String) {
        print("Received decrypted transmission.")
    }
}

Running the Salut Client

Similarly to the server, just initialize a client on your device, from which you want to send information, with:

let client = SalutClient(peerId: id, password: code)
client.prepare()
client.delegate = self

The client has its own SalutClientDelegate as well. Here is an example with a host controller named ConnectionController:

extension ConnectionController: SalutClientDelegate {
    func client(_ client: SalutClient, didChangeConnectedDevices connectedDevices: [String]) {
        print("Client did change connected devices: \(connectedDevices)")
    }
    
    func client(_ client: SalutClient, sentSearchRequest package: Package) {
        print("Client sent search request: \(package.description)")
    }
    
    func client(_ client: SalutClient, receivedSearchResponse package: Package) {
        print("Client received search response: \(package.description)")
    }
    
    func client(_ client: SalutClient, recievedDecryptableSearchResponse response: String) {
        print("Client received decryptable search response: \(response)")
    }
    
    func client(_ client: SalutClient, sentData package: Package) {
        print("Client sent data: \(package.description)")
    } 
}

Setting the password on running clients or servers

To reset your password on the fly, simply call:

// Server
server.setPassword(newCode)
// Client
client.setPassword(newCode)

Establishing a connection

Have your server and your client running. On your client, call:

salut.sendSearchRequest()

If the password is correct and the server gets the message, he will respond to the client. The client then calls the delegate method:

func client(_ client: SalutClient, recievedDecryptableSearchResponse response: String) {
    // Handle successful connection, e.g. save password and start sending messages
}

Sending data

When you established a connection or your password always is the same and therefore you do not have to check for password correctness first, call:

salut.sendData(dataString)

On your server, the data will be received and decrypted. Use the server delegate method

func server(_ server: SalutServer, receivedDecryptedTransmission data: String) {
    // Handle data
}

Contribution

Feel free to contribute to my project, just open a Pull Request!

License

MIT License

Copyright (c) 2018 Philipp Matthes

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.