Secure Battleship Game

[Envoy-VC]

BattleshipX is a secure and private battleship game that can be played with friends.

Showcase Link: https://ethglobal.com/showcase/battleshipx-0gc9h

How nillion is used?

While storing the secret game state in nillion, it is stored as follows:

{
	"carrier": [101, 102, 103, 104, 105],
	"battleship": [112, 113, 114, 115],
	"cruiser": [121, 122, 123],
	"submarine": [165, 175, 185],
	"destroyer": [191, 192]
}

where each number is 1XY where X is the row number and Y is the column number. The game state is stored in nillion in encrypted form. X and Y are in range of 0-9.

Why extra 1 at start? The extra 1 is added to make the number 3 digit as zero at the X position will be ignored by the game logic.

When a user attacks a position, the user sends the position to the contract.

For Example: User attacks position 7, 5. The contract will compute the attack with position 175, the computation starts at 1 and multiplies it by (value - position)

This is done through Array.reduce method. The logic is if there is a ship at that position, somewhere in the computation value == position and the result becomes 0. If the result is 0, the user has hit the ship.

---

Here is the entire nada program

from nada_dsl import *


def nada_main():
    party1 = Party(name="Party1")
    """
    Input for Each Ship co-ordinates
    
    Coordinates for Carrier: 5
    Coordinates for Battleship: 4
    Coordinates for Cruiser: 3
    Coordinates for Submarine: 3
    Coordinates for Destroyer: 2
    
    Each co-ordinate is a SecretInteger of form 1XY where X is the row number and Y is the column number (0,9)
    
    Position is the attack co-ordinate of form 1XY where X is the row number and Y is the column number (0,9)
    
    
    How attack is determined:
    
    For each ship we run a reduce function with accumulator as Previous Result. The reduce function returns
    Previous Result * (position - current_value) for each value in the ship coordinates.
    
    So if the attack co-ordinate is present in the ship coordinates, the result will be 0 and further reduce will return 0.
    """
    carrier = Array(SecretInteger(Input(name="carrier", party=party1)), size=5)
    battleship = Array(SecretInteger(
        Input(name="battleship", party=party1)), size=4)
    cruiser = Array(SecretInteger(Input(name="cruiser", party=party1)), size=3)
    submarine = Array(SecretInteger(
        Input(name="submarine", party=party1)), size=3)
    destroyer = Array(SecretInteger(
        Input(name="destroyer", party=party1)), size=2)

    position = SecretInteger(Input(name="position", party=party1))

    @nada_fn
    def check_exists(a: SecretInteger, b: SecretInteger) -> SecretInteger:
        return a * (b - position)

    result1 = carrier.reduce(check_exists, Integer(1))
    result2 = battleship.reduce(check_exists, result1)
    result3 = cruiser.reduce(check_exists, result2)
    result4 = submarine.reduce(check_exists, result3)
    result5 = destroyer.reduce(check_exists, result4)

    result = result5 * result5

    out = Output(result, "out", party1)

    return [out]

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The entre nillion methods are served through a FastAPI Server created in Python

https://github.com/Envoy-VC/battleship-x/tree/main/packages/api