pub struct RandomnessFromOneEpochAgo<T>(_);
Expand description

Randomness usable by on-chain code that does not depend upon finality and takes action based upon on-chain commitments made during the previous epoch.

All randomness is relative to commitments to any other inputs to the computation: If Alice samples randomness near perfectly using radioactive decay, but then afterwards Eve selects an arbitrary value with which to xor Alice’s randomness, then Eve always wins whatever game they play.

All input commitments used with RandomnessFromOneEpochAgo should come from at least two epochs ago, although the previous epoch might work in special cases under additional assumption.

All users learn RandomnessFromOneEpochAgo at the end of the previous epoch, although some block producers learn it several block earlier.

Adversaries with enough block producers could bias this randomness by choosing upon what their block producers build at either the end of the previous epoch or the beginning of the current epoch, or electing to skipping some of their own block production slots towards the end of the previous epoch.

Adversaries should not possess many block production slots towards the beginning or end of every epoch, but they possess some influence over when they possess more slots.

As an example usage, we determine parachain auctions ending times in Polkadot using RandomnessFromOneEpochAgo because it reduces bias from ParentBlockRandomness and does not require the extra finality delay of RandomnessFromTwoEpochsAgo.

Trait Implementations§

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impl<T: Config> Randomness<<T as Config>::Hash, <<<T as Config>::Block as HeaderProvider>::HeaderT as Header>::Number> for RandomnessFromOneEpochAgo<T>

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fn random(subject: &[u8]) -> (T::Hash, BlockNumberFor<T>)

Get the most recently determined random seed, along with the time in the past since when it was determinable by chain observers. Read more
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fn random_seed() -> (Output, BlockNumber)

Get the basic random seed. Read more

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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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>,

Convert from a value of T into an equivalent instance of Option<Self>. Read more
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fn checked_into<T>(self) -> Option<T>where Self: TryInto<T>,

Consume self to return Some equivalent value of Option<T>. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for Twhere U: From<T>,

const: unstable · source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IsType<T> for T

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fn from_ref(t: &T) -> &T

Cast reference.
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fn into_ref(&self) -> &T

Cast reference.
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fn from_mut(t: &mut T) -> &mut T

Cast mutable reference.
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fn into_mut(&mut self) -> &mut T

Cast mutable reference.
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impl<T, Outer> IsWrappedBy<Outer> for Twhere Outer: AsRef<T> + AsMut<T> + From<T>, T: From<Outer>,

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fn from_ref(outer: &Outer) -> &T

Get a reference to the inner from the outer.

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fn from_mut(outer: &mut Outer) -> &mut T

Get a mutable reference to the inner from the outer.

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impl<T> Pointable for T

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const ALIGN: usize = mem::align_of::<T>()

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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impl<T> Same<T> for T

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type Output = T

Should always be Self
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impl<T> SaturatedConversion for T

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fn saturated_from<T>(t: T) -> Selfwhere Self: UniqueSaturatedFrom<T>,

Convert from a value of T into an equivalent instance of Self. Read more
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fn saturated_into<T>(self) -> Twhere Self: UniqueSaturatedInto<T>,

Consume self to return an equivalent value of T. Read more
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impl<SS, SP> SupersetOf<SS> for SPwhere SS: SubsetOf<SP>,

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fn to_subset(&self) -> Option<SS>

The inverse inclusion map: attempts to construct self from the equivalent element of its superset. Read more
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fn is_in_subset(&self) -> bool

Checks if self is actually part of its subset T (and can be converted to it).
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fn to_subset_unchecked(&self) -> SS

Use with care! Same as self.to_subset but without any property checks. Always succeeds.
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fn from_subset(element: &SS) -> SP

The inclusion map: converts self to the equivalent element of its superset.
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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<S, T> UncheckedInto<T> for Swhere T: UncheckedFrom<S>,

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fn unchecked_into(self) -> T

The counterpart to unchecked_from.
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impl<T, S> UniqueSaturatedInto<T> for Swhere T: Bounded, S: TryInto<T>,

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fn unique_saturated_into(self) -> T

Consume self to return an equivalent value of T.
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impl<V, T> VZip<V> for Twhere V: MultiLane<T>,

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fn vzip(self) -> V

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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>where S: Into<Dispatch>,

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Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
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impl<T> JsonSchemaMaybe for T

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impl<T> MaybeRefUnwindSafe for Twhere T: RefUnwindSafe,