StringObfuscator.swift

import Foundation

public final class Obfuscator {
    /// The salt used to obfuscate and reveal the string.
    static let salt: String = "\(String(describing: Obfuscator.self))\(String(describing: NSObject.self))"

    /**
     This method obfuscates the string passed in using the salt
     that was used when the Obfuscator was initialized.
     
     - parameter string: the string to obfuscate
     
     - returns: the obfuscated string in a byte array
     */
    public class func bytesByObfuscatingString(string: String) -> [UInt8] {
        let text = [UInt8](string.utf8)
        let cipher = [UInt8](self.salt.utf8)
        let length = cipher.count
        
        var encrypted = [UInt8]()
        
        for t in text.enumerated() {
            encrypted.append(t.element ^ cipher[t.offset % length])
        }
        
        Logger.debug?.message("obfuscated: \(String(bytes: encrypted, encoding: .utf8) ?? "")")
        return encrypted
    }
    
    /**
     This method reveals the original string from the obfuscated
     byte array passed in. The salt must be the same as the one
     used to encrypt it in the first place.
     
     - parameter key: the byte array to reveal
     
     - returns: the original string
     */
    public class func reveal(key: [UInt8]) -> String {
        let cipher = [UInt8](self.salt.utf8)
        let length = cipher.count
        
        var decrypted = [UInt8]()
        
        for k in key.enumerated() {
            decrypted.append(k.element ^ cipher[k.offset % length])
        }
        
        guard let string = String(bytes: decrypted, encoding: .utf8) else {
            fatalError("Cannot reveal")
        }
        return string
    }
}