How to resolve the algorithm OpenWebNet password step by step in the Java programming language
How to resolve the algorithm OpenWebNet password step by step in the Java programming language
Table of Contents
Problem Statement
Calculate the password requested by ethernet gateways from the Legrand / Bticino MyHome OpenWebNet home automation system when the user's ip address is not in the gateway's whitelist Note: Factory default password is '12345'. Changing it is highly recommended ! conversation goes as follows at which point a password should be sent back, calculated from the "password open" that is set in the gateway, and the nonce that was just sent
Let's start with the solution:
Step by Step solution about How to resolve the algorithm OpenWebNet password step by step in the Java programming language
The provided Java code defines a method ownPasswordCalculation to calculate a value based on a given password and a nonce (a random value). The calculation involves a series of bitwise operations and shifts based on the characters in the nonce. Let's break down the code step by step:
-
Constants: The code defines several constants:
m1: Constant with hexadecimal value0xFFFF_FFFFL, representing a 32-bit mask with all bits set to 1, used to mask the result to 32 bits.m8: Constant with hexadecimal value0xFFFF_FFF8L, representing a 32-bit mask with all bits set to 1 except the last 3 bits.m16: Constant with hexadecimal value0xFFFF_FFF0L, representing a 32-bit mask with all bits set to 1 except the last 4 bits.m128: Constant with hexadecimal value0xFFFF_FF80L, representing a 32-bit mask with all bits set to 1 except the last 7 bits.m16777216: Constant with hexadecimal value0xFF00_0000L, representing a 32-bit mask with only the 16 most significant bits set to 1.
-
Variables: The code initializes several variables:
flag: A boolean flag, initially set totrue, used to determine when to use the password value.number1andnumber2: Long variables used to perform the calculations and store intermediate results.
-
Nonce Loop: The code enters a loop that iterates through each character in the provided nonce string:
- For each character, it performs a series of actions based on the character:
- If the character is '1', it checks the
flagvariable. Ifflagistrue, it setsnumber2to the password value. Then, it setsflagtofalseand performs some bitwise operations and shifts onnumber1andnumber2. - Similar actions are taken for characters '2', '3', '4', '5', '6', '7', '8', and '9', each performing specific bitwise operations and shifts based on the character.
- For any other characters, it simply sets
number1tonumber2.
- If the character is '1', it checks the
- After processing the current character, it updates
number2to the value ofnumber1.
- For each character, it performs a series of actions based on the character:
-
Final Calculation: After processing all characters in the nonce, the code returns the value of
number1masked bym1to ensure it is a 32-bit value. -
Main Method: The
mainmethod includes some test cases to demonstrate theownPasswordCalculationmethod by comparing the calculated result with expected values.
In summary, this code performs a series of complex bitwise operations and shifts on a password and a nonce to calculate a specific value. The exact calculation depends on the characters in the nonce string and follows a specific set of rules. The final result is a 32-bit value that is influenced by the input password and the order of characters in the nonce.
Source code in the java programming language
public static void main(String[] aArgs) {
ownPasswordCalculationTest("12345", "603356072", 25280520);
ownPasswordCalculationTest("12345", "410501656", 119537670);
}
private static void ownPasswordCalculationTest(String password, String nonce, long expected) {
final long result = ownPasswordCalculation(Long.valueOf(password), nonce);
String message = password + " " + nonce + " " + result + " " + expected;
System.out.println( ( result == expected ) ? "PASS " + message : "FAIL " + message );
}
private static long ownPasswordCalculation(long password, String nonce) {
final long m1 = 0xFFFF_FFFFL;
final long m8 = 0xFFFF_FFF8L;
final long m16 = 0xFFFF_FFF0L;
final long m128 = 0xFFFF_FF80L;
final long m16777216 = 0xFF00_0000L;
boolean flag = true;
long number1 = 0;
long number2 = 0;
for ( char ch : nonce.toCharArray() ) {
number2 = number2 & m1;
switch (ch) {
case '1' -> {
if ( flag ) { number2 = password; }
flag = false;
number1 = number2 & m128;
number1 = number1 >>> 7;
number2 = number2 << 25;
number1 = number1 + number2;
}
case '2' -> {
if ( flag ) { number2 = password; }
flag = false;
number1 = number2 & m16;
number1 = number1 >>> 4;
number2 = number2 << 28;
number1 = number1 + number2;
}
case '3' -> {
if ( flag ) { number2 = password; }
flag = false;
number1 = number2 & m8;
number1 = number1 >>> 3;
number2 = number2 << 29;
number1 = number1 + number2;
}
case '4' -> {
if ( flag ) { number2 = password; }
flag = false;
number1 = number2 << 1;
number2 = number2 >>> 31;
number1 = number1 + number2;
}
case '5' -> {
if ( flag ) { number2 = password; }
flag = false;
number1 = number2 << 5;
number2 = number2 >>> 27;
number1 = number1 + number2;
}
case '6' -> {
if ( flag ) { number2 = password; }
flag = false;
number1 = number2 << 12;
number2 = number2 >>> 20;
number1 = number1 + number2;
}
case '7' -> {
if ( flag ) { number2 = password; }
flag = false;
number1 = number2 & 0xFF00L;
number1 = number1 + ( ( number2 & 0xFFL ) << 24 );
number1 = number1 + ( ( number2 & 0xFF0000L ) >>> 16 );
number2 = ( number2 & m16777216 ) >>> 8;
number1 = number1 + number2;
}
case '8' -> {
if ( flag ) { number2 = password;}
flag = false;
number1 = number2 & 0xFFFFL;
number1 = number1 << 16;
number1 = number1 + ( number2 >>> 24 );
number2 = number2 & 0xFF0000L;
number2 = number2 >>> 8;
number1 = number1 + number2;
}
case '9' -> {
if ( flag ) { number2 = password; }
flag = false;
number1 = ~number2;
}
default -> number1 = number2;
}
number2 = number1;
}
return number1 & m1;
}
}
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