Hashed password for serial device

General
1

Hi, i'm trying to create a node to read an old serial device (RS232), i need to crate a function node which will change the Hex input to a new output so the device will accept the password.
Example
This is the password seed generated from the device:
Seed = 73 8C FA 08 BF 6C 84 F6 (Response from serial device, this variable changes all the time)
Password = 41 42 43 44 30 30 32
New password = Password ^ seed (X0R), This gives:
32 CE B9 4C 8F 5C B4 C4
I then need to + the last bit to the XOR
last = New password[7]
Final = New Password + last &0FF= F6C47DC958B4682C

How do i get from 738CFA08BF6C84F6 to F6C47DC958B4682C using a function node

2

Hi,
there are some questions left:
how do your payloads come in (seed and password)?

do the come in as hex/dec? do they come in as one concatenated string? do they come in as an array of seven strings? thats what the message handling will be all about.

3

You got me courious to try this during lunchtime:

here is a function that does the basics of what you asked, the probably "hard" part:

seed = ["73", "8C", "FA", "08", "BF", "6C", "84", "F6"];
password = ["41", "42", "43", "44", "30", "30", "32"];
let passdec = [];
let seeddec = [];
let newpass = [];

//------------------------------------------------
// define function to convert between bases
function decToHex(num){
    var hex = "";
    var temp = num;
    table = ["0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"];
    rest = temp%16;
    while(temp > 0){
        temp = Math.floor(temp / 16);
        if(temp > 1){
        hex = hex + table[temp];
        }else{
            hex  = hex + table[rest];
        }
    }


    return hex;
}

//--------------------------------------------------

for (i=0;i<seed.length;i++){
    seed[i] = "0x"+seed[i]; //by 0x[number] tell NR this is a hex number
    seeddec[i] = parseInt(seed[i]); //parse a decimal number
 
}

for (i=0;i<password.length;i++){
    passdec[i] = parseInt(password[i]); //parse the decimals from password but the are stored as binary anyway (no quantum computing ;)
    newpass[i] = seeddec[i]^passdec[i]; //do the XOR stuff
    newpass[i] = decToHex(newpass[i]); // convert to hex
    
}


msg.payload = {passdec:passdec, seeddec:seeddec, seedhex:seed, newpass:newpass};
return msg;
1 Like
4

Thanks for you quick response!!
How do the payloads come in? Only the seed comes in from the payload (hex), I then need to add the password and push through the function.

It comes as a in as hex (buffer) so...
Node Red (Ask for seed)........> (i have this command set)
Serial device <......[73 8C FA 08 BF 6C 84 F6]
Function node (Do the clever stuff i.e. add password, XOR, +bit, &0FF)....[F6 C4 7D C9 58 B4 68 2C]...>
Accepted<............
I will test your function and see how i get on!!

5

When i test this function i get "5A""A6""D1""24""A1""72""A4" as the output.

I feel close to the answer tho! this is function in C++

string ElsterEncrypt(string password, string seed)
{
//Convert hex string to byte array.
byte s = GXCommon.HexToBytes(seed, false);
byte crypted = new byte[8];
for (int pos = 0; pos != 8; ++pos)
{
crypted[pos] = (byte)(password[pos] ^ s[pos]);
}
int last = crypted[7];
for (int pos = 0; pos != 8; ++pos)
{
crypted[pos] = (byte)((crypted[pos] + last) & 0xFF);
last = crypted[pos];
}
return GXCommon.ToHex(crypted, false);
}

1 Like
6

Yes what I wrote you is no final hash function. I only did the conversion of hex to dec, the xor and reconversion to hex. Let's take the first position (seed[0]&password[0]) as an example.

Js is not intended to be c++ in many matters. It gifts the unnecessarity of declaring data types, but it costs not having built-in functions for many operations. so mathematical Programms can easily have 200% of code compared to c++ (in which I am absolutely no pro, like in any language ;))

1 Like
7

73hex is 7*16+3 = 115dec which ist correct
41dec is 41dec.
115dec =
1 1 1 0 0 1 1 bin
0 1 0 1 0 0 1bin
41 dec =
XOR: 1011010
which is 2+8+16+64 = 90
90 = 5 x16+10 = 5Ahex
which is correct :sweat_smile:

or did i understand something wrong?
at least it works like i understood it :slight_smile:

what i didnt implement was the 0xFF append.

JS will fill missing zeros automatically when xor#ing decimals to byte, so thos cant be the problem.
you are doing the steps in your c++ positionwise, as i expected. so that cant be the problem either.

what i didnt do in the function is this.

crypted[pos] = (byte)((crypted[pos] + last) & 0xFF);

thats what you would have to implement yourself.

probably in JS something like

last = newpass[newpass.length-1]; // ==newpass[7]
for(i=0;i<8;i++){
newpass[i] = newpass[i] + last;
//and then
newpass[i] = decToHex(newpass[i]);:
}

looks like a checksum, right?

8

Did you get it going?