I am trying to convert my Android app to iOS. This will be my first iOS app. I can't seem to translate this code properly. If someone wouldn't mind showing me how its done, that would be greatly appreciated.

//scrambBase20 is a Byte array
String descramble(String input){
    char[] ret;
    ret = input.toCharArray();
    int offset = -scrambBase20.length;
    for(int i=0;i<input.length();i++){
        if(i%scrambBase20.length==0)
            offset+=scrambBase20.length;
        ret[scrambBase20[i%scrambBase20.length]+offset]=(char) ((byte) (input.charAt(i))^0x45);
    }

    String realRet = "";
    for (char x : ret){
        realRet+=x;
    }
    realRet = realRet.trim();
    return realRet;
}