Dia Randomness Oracle

Randomness in Blockchain

Randomness in blockchains is crucial for a fair and unpredictable distribution of validator responsibilities. Computers are deterministic devices, meaning the same input always produces the same output, making true randomness difficult to achieve. What is commonly referred to as random numbers on a computer are actually pseudo-random. These numbers depend on a sufficiently random seed provided by the user or another type of oracle, such as a weather station for atmospheric noise, heart rate, or even lava lamps. From this seed, a series of seemingly random numbers can be generated, but given the same seed, the same sequence will always be produced.

However, there are distributed systems that try to solve the problem of "predictability" of randomness, one of which is drand.

The given dia-oracle implementation is an example of safe randomization. The source code, developed using the Sails framework, is available on GitHub.

State

The Random structure stores a random value, its cryptographic signature, and the signature of the previous value, ensuring integrity and traceability.

oracle/randomness/app/src/lib.rs

pub struct Random {
    pub randomness: RandomSeed,
    pub signature: String,
    pub prev_signature: String,
}

The RandomnessOracle structure maintains the overall oracle state, tracking ownership, stored random values, the last updated round, and the manager responsible for updates.

oracle/randomness/app/src/lib.rs

pub struct RandomnessOracle {
    pub owner: ActorId,
    pub values: HashMap<u128, Random>,
    pub last_round: u128,
    pub manager: ActorId,
}

Actions

oracle/randomness/app/src/lib.rs

    pub fn set_random_value(&mut self, round: u128, value: Random);
    pub fn get_last_round_with_random_value(&mut self) -> (u128, u128);
    pub fn update_manager(&mut self, new_manager: ActorId);

• The set_random_value method securely assigns a new random value to a specific round, ensuring sequential updates.
• The get_last_round_with_random_value method retrieves the most recent round and its associated random value.
• The update_manager method changes the manager, allowing controlled delegation of responsibility.

oracle/randomness/app/src/lib.rs

    pub fn get_owner(&self) -> ActorId;
    pub fn get_last_round(&self) -> u128;
    pub fn get_manager(&self) -> ActorId;
    pub fn get_values(&self) -> Vec<(u128, Random)>;

Methods like get_owner, get_last_round, get_manager, and get_values provide convenient access to the oracle's current state.

Events

The Event enum defines key events: updating the manager, adding a new random value, and retrieving the last round's random value, ensuring clear system behavior tracking.

oracle/randomness/app/src/lib.rs

    pub enum Event {
        NewManager(ActorId),
        NewRandomValue { round: u128, value: Random },
        LastRoundWithRandomValue { round: u128, random_value: u128 },
    }

Initialisation

The init method initializes the oracle with the given manager and sets up its default state, defining ownership and control.

oracle/randomness/app/src/lib.rs

    pub async fn init(manager: ActorId) -> Self {
        unsafe {
            RANDOMNESS_ORACLE = Some(RandomnessOracle {
                owner: msg::source(),
                manager,
                ..Default::default()
            });
        }
        Self(())
    }

Conclusion

The source code of this example of a Dia Randomness Oracle program is available on GitHub: gear-foundation/dapps/contracts/oracle/randomness.

See also an example of the program testing implementation based on gtest: gear-foundation/dapps/contracts/oracle/randomness/tests/gtest.rs.

For more details about testing programs written on Vara, refer to this article: Program Testing.