[−][src]Struct pallet_randomness_collective_flip::Module
Methods
impl<T: Trait + 'static> Module<T>
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pub fn random_material() -> Vec<T::Hash>
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Series of block headers from the last 81 blocks that acts as random seed material. This
is arranged as a ring buffer with block_number % 81
being the index into the Vec
of
the oldest hash.
Trait Implementations
impl<T: Trait> Callable<T> for Module<T>
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impl<T: Clone + Trait> Clone for Module<T>
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impl<T: Copy + Trait> Copy for Module<T>
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impl<T: Trait> Debug for Module<T> where
T: Debug,
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T: Debug,
impl<T: Eq + Trait> Eq for Module<T>
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impl<T: Trait> ModuleErrorMetadata for Module<T>
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fn metadata() -> &'static [ErrorMetadata]
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impl<T: Trait> OffchainWorker<<T as Trait>::BlockNumber> for Module<T>
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fn offchain_worker(_n: BlockNumber)
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impl<T: Trait> OnFinalize<<T as Trait>::BlockNumber> for Module<T>
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fn on_finalize(_n: BlockNumber)
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impl<T: Trait> OnInitialize<<T as Trait>::BlockNumber> for Module<T>
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fn on_initialize(block_number: T::BlockNumber) -> Weight
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impl<T: Trait> OnRuntimeUpgrade for Module<T>
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fn on_runtime_upgrade() -> u32
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impl<T: PartialEq + Trait> PartialEq<Module<T>> for Module<T>
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impl<T: Trait> Randomness<<T as Trait>::Hash> for Module<T>
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fn random(subject: &[u8]) -> T::Hash
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Get a low-influence "random" value.
Being a deterministic block chain, real randomness is difficult to come by. This gives you
something that approximates it. subject
is a context identifier and allows you to get a
different result to other callers of this function; use it like
random(&b"my context"[..])
. This is initially implemented through a low-influence
"triplet mix" convolution of previous block hash values. In the future it will be generated
from a secure verifiable random function (VRF).
Security Notes
This randomness uses a low-influence function, drawing upon the block hashes from the previous 81 blocks. Its result for any given subject will be known far in advance by anyone observing the chain. Any block producer has significant influence over their block hashes bounded only by their computational resources. Our low-influence function reduces the actual block producer's influence over the randomness, but increases the influence of small colluding groups of recent block producers.
Some BABE blocks have VRF outputs where the block producer has exactly one bit of influence, either they make the block or they do not make the block and thus someone else makes the next block. Yet, this randomness is not fresh in all BABE blocks.
If that is an insufficient security guarantee then two things can be used to improve this randomness:
- Name, in advance, the block number whose random value will be used; ensure your module retains a buffer of previous random values for its subject and then index into these in order to obviate the ability of your user to look up the parent hash and choose when to transact based upon it.
- Require your user to first commit to an additional value by first posting its hash. Require them to reveal the value to determine the final result, hashing it with the output of this random function. This reduces the ability of a cabal of block producers from conspiring against individuals.
WARNING: Hashing the result of this function will remove any low-influence properties it has
and mean that all bits of the resulting value are entirely manipulatable by the author of
the parent block, who can determine the value of parent_hash
.
fn random_seed() -> Output
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impl<T: Trait> StructuralEq for Module<T>
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impl<T: Trait> StructuralPartialEq for Module<T>
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Auto Trait Implementations
impl<T> RefUnwindSafe for Module<T> where
T: RefUnwindSafe,
T: RefUnwindSafe,
impl<T> Send for Module<T> where
T: Send,
T: Send,
impl<T> Sync for Module<T> where
T: Sync,
T: Sync,
impl<T> Unpin for Module<T> where
T: Unpin,
T: Unpin,
impl<T> UnwindSafe for Module<T> where
T: UnwindSafe,
T: UnwindSafe,
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> CheckedConversion for T
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fn checked_from<T>(t: T) -> Option<Self> where
Self: TryFrom<T>,
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Self: TryFrom<T>,
fn checked_into<T>(self) -> Option<T> where
Self: TryInto<T>,
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Self: TryInto<T>,
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, Outer> IsWrappedBy<Outer> for T where
Outer: AsRef<T> + AsMut<T> + From<T>,
T: From<Outer>,
Outer: AsRef<T> + AsMut<T> + From<T>,
T: From<Outer>,
fn from_ref(outer: &Outer) -> &T
Get a reference to the inner from the outer.
fn from_mut(outer: &mut Outer) -> &mut T
Get a mutable reference to the inner from the outer.
impl<T> MaybeDebug for T where
T: Debug,
T: Debug,
impl<T> MaybeDebug for T where
T: Debug,
T: Debug,
impl<T> MaybeRefUnwindSafe for T where
T: RefUnwindSafe,
T: RefUnwindSafe,
impl<T> Member for T where
T: 'static + Clone + PartialEq<T> + Eq + Send + Sync + Debug,
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T: 'static + Clone + PartialEq<T> + Eq + Send + Sync + Debug,
impl<T> Same<T> for T
type Output = T
Should always be Self
impl<T> SaturatedConversion for T
fn saturated_from<T>(t: T) -> Self where
Self: UniqueSaturatedFrom<T>,
Self: UniqueSaturatedFrom<T>,
fn saturated_into<T>(self) -> T where
Self: UniqueSaturatedInto<T>,
Self: UniqueSaturatedInto<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
type Owned = T
The resulting type after obtaining ownership.
fn to_owned(&self) -> T
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fn clone_into(&self, target: &mut T)
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<S, T> UncheckedInto<T> for S where
T: UncheckedFrom<S>,
T: UncheckedFrom<S>,
fn unchecked_into(self) -> T
impl<T, S> UniqueSaturatedInto<T> for S where
S: TryInto<T>,
T: Bounded,
S: TryInto<T>,
T: Bounded,
fn unique_saturated_into(self) -> T
impl<V, T> VZip<V> for T where
V: MultiLane<T>,
V: MultiLane<T>,