Struct pallet_babe::RandomnessFromTwoEpochsAgo
source · pub struct RandomnessFromTwoEpochsAgo<T>(_);Expand description
Randomness usable by consensus protocols that depend upon finality and take action based upon on-chain commitments made during the epoch before the previous epoch.
An off-chain consensus protocol requires randomness be finalized before usage, but one
extra epoch delay beyond RandomnessFromOneEpochAgo suffices, under the assumption
that finality never stalls for longer than one 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 RandomnessFromTwoEpochsAgo should come from at least
three epochs ago. We require BABE session keys be registered at least three epochs
before being used to derive ParentBlockRandomness for example.
All users learn RandomnessFromTwoEpochsAgo when epoch current_epoch - 1 starts,
although some learn it a few block earlier inside epoch current_epoch - 2.
Adversaries with enough block producers could bias this randomness by choosing upon
what their block producers build at the end of epoch current_epoch - 2 or the
beginning epoch current_epoch - 1, or skipping slots at the end of epoch
current_epoch - 2.
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.
Trait Implementations§
source§impl<T: Config> Randomness<<T as Config>::Hash, <T as Config>::BlockNumber> for RandomnessFromTwoEpochsAgo<T>
impl<T: Config> Randomness<<T as Config>::Hash, <T as Config>::BlockNumber> for RandomnessFromTwoEpochsAgo<T>
source§fn random(subject: &[u8]) -> (T::Hash, T::BlockNumber)
fn random(subject: &[u8]) -> (T::Hash, T::BlockNumber)
Get the most recently determined random seed, along with the time in the past
since when it was determinable by chain observers. Read more
source§fn random_seed() -> (Output, BlockNumber)
fn random_seed() -> (Output, BlockNumber)
Get the basic random seed. Read more
Auto Trait Implementations§
impl<T> RefUnwindSafe for RandomnessFromTwoEpochsAgo<T>where
T: RefUnwindSafe,
impl<T> Send for RandomnessFromTwoEpochsAgo<T>where
T: Send,
impl<T> Sync for RandomnessFromTwoEpochsAgo<T>where
T: Sync,
impl<T> Unpin for RandomnessFromTwoEpochsAgo<T>where
T: Unpin,
impl<T> UnwindSafe for RandomnessFromTwoEpochsAgo<T>where
T: UnwindSafe,
Blanket Implementations§
source§impl<T> CheckedConversion for T
impl<T> CheckedConversion for T
source§impl<T> Downcast for Twhere
T: Any,
impl<T> Downcast for Twhere
T: Any,
source§fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>
fn into_any(self: Box<T, Global>) -> Box<dyn Any + 'static, Global>
Convert
Box<dyn Trait> (where Trait: Downcast) to Box<dyn Any>. Box<dyn Any> can
then be further downcast into Box<ConcreteType> where ConcreteType implements Trait. Read moresource§fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
fn into_any_rc(self: Rc<T>) -> Rc<dyn Any + 'static>
Convert
Rc<Trait> (where Trait: Downcast) to Rc<Any>. Rc<Any> can then be
further downcast into Rc<ConcreteType> where ConcreteType implements Trait. Read moresource§fn as_any(&self) -> &(dyn Any + 'static)
fn as_any(&self) -> &(dyn Any + 'static)
Convert
&Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot
generate &Any’s vtable from &Trait’s. Read moresource§fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)
Convert
&mut Trait (where Trait: Downcast) to &Any. This is needed since Rust cannot
generate &mut Any’s vtable from &mut Trait’s. Read moresource§impl<T> FmtForward for T
impl<T> FmtForward for T
source§fn fmt_binary(self) -> FmtBinary<Self>where
Self: Binary,
fn fmt_binary(self) -> FmtBinary<Self>where
Self: Binary,
source§fn fmt_display(self) -> FmtDisplay<Self>where
Self: Display,
fn fmt_display(self) -> FmtDisplay<Self>where
Self: Display,
source§fn fmt_lower_exp(self) -> FmtLowerExp<Self>where
Self: LowerExp,
fn fmt_lower_exp(self) -> FmtLowerExp<Self>where
Self: LowerExp,
source§fn fmt_lower_hex(self) -> FmtLowerHex<Self>where
Self: LowerHex,
fn fmt_lower_hex(self) -> FmtLowerHex<Self>where
Self: LowerHex,
source§fn fmt_pointer(self) -> FmtPointer<Self>where
Self: Pointer,
fn fmt_pointer(self) -> FmtPointer<Self>where
Self: Pointer,
source§fn fmt_upper_exp(self) -> FmtUpperExp<Self>where
Self: UpperExp,
fn fmt_upper_exp(self) -> FmtUpperExp<Self>where
Self: UpperExp,
source§fn fmt_upper_hex(self) -> FmtUpperHex<Self>where
Self: UpperHex,
fn fmt_upper_hex(self) -> FmtUpperHex<Self>where
Self: UpperHex,
source§impl<T> Instrument for T
impl<T> Instrument for T
source§fn instrument(self, span: Span) -> Instrumented<Self>
fn instrument(self, span: Span) -> Instrumented<Self>
source§fn in_current_span(self) -> Instrumented<Self>
fn in_current_span(self) -> Instrumented<Self>
source§impl<T, Outer> IsWrappedBy<Outer> for Twhere
Outer: AsRef<T> + AsMut<T> + From<T>,
T: From<Outer>,
impl<T, Outer> IsWrappedBy<Outer> for Twhere
Outer: AsRef<T> + AsMut<T> + From<T>,
T: From<Outer>,
source§impl<T> Pipe for Twhere
T: ?Sized,
impl<T> Pipe for Twhere
T: ?Sized,
source§fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> Rwhere
Self: Sized,
fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> Rwhere
Self: Sized,
Pipes by value. This is generally the method you want to use. Read more
source§fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> Rwhere
R: 'a,
fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> Rwhere
R: 'a,
Borrows
self and passes that borrow into the pipe function. Read moresource§fn pipe_ref_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> Rwhere
R: 'a,
fn pipe_ref_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> Rwhere
R: 'a,
Mutably borrows
self and passes that borrow into the pipe function. Read moresource§fn pipe_borrow<'a, B, R>(&'a self, func: impl FnOnce(&'a B) -> R) -> Rwhere
Self: Borrow<B>,
B: 'a + ?Sized,
R: 'a,
fn pipe_borrow<'a, B, R>(&'a self, func: impl FnOnce(&'a B) -> R) -> Rwhere
Self: Borrow<B>,
B: 'a + ?Sized,
R: 'a,
source§fn pipe_borrow_mut<'a, B, R>(
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> Rwhere
Self: BorrowMut<B>,
B: 'a + ?Sized,
R: 'a,
fn pipe_borrow_mut<'a, B, R>(
&'a mut self,
func: impl FnOnce(&'a mut B) -> R
) -> Rwhere
Self: BorrowMut<B>,
B: 'a + ?Sized,
R: 'a,
source§fn pipe_as_ref<'a, U, R>(&'a self, func: impl FnOnce(&'a U) -> R) -> Rwhere
Self: AsRef<U>,
U: 'a + ?Sized,
R: 'a,
fn pipe_as_ref<'a, U, R>(&'a self, func: impl FnOnce(&'a U) -> R) -> Rwhere
Self: AsRef<U>,
U: 'a + ?Sized,
R: 'a,
Borrows
self, then passes self.as_ref() into the pipe function.source§fn pipe_as_mut<'a, U, R>(&'a mut self, func: impl FnOnce(&'a mut U) -> R) -> Rwhere
Self: AsMut<U>,
U: 'a + ?Sized,
R: 'a,
fn pipe_as_mut<'a, U, R>(&'a mut self, func: impl FnOnce(&'a mut U) -> R) -> Rwhere
Self: AsMut<U>,
U: 'a + ?Sized,
R: 'a,
source§impl<T> Pointable for T
impl<T> Pointable for T
source§impl<T> SaturatedConversion for T
impl<T> SaturatedConversion for T
source§fn saturated_from<T>(t: T) -> Selfwhere
Self: UniqueSaturatedFrom<T>,
fn saturated_from<T>(t: T) -> Selfwhere
Self: UniqueSaturatedFrom<T>,
source§fn saturated_into<T>(self) -> Twhere
Self: UniqueSaturatedInto<T>,
fn saturated_into<T>(self) -> Twhere
Self: UniqueSaturatedInto<T>,
Consume self to return an equivalent value of
T. Read moresource§impl<SS, SP> SupersetOf<SS> for SPwhere
SS: SubsetOf<SP>,
impl<SS, SP> SupersetOf<SS> for SPwhere
SS: SubsetOf<SP>,
source§fn to_subset(&self) -> Option<SS>
fn to_subset(&self) -> Option<SS>
The inverse inclusion map: attempts to construct
self from the equivalent element of its
superset. Read moresource§fn is_in_subset(&self) -> bool
fn is_in_subset(&self) -> bool
Checks if
self is actually part of its subset T (and can be converted to it).source§fn to_subset_unchecked(&self) -> SS
fn to_subset_unchecked(&self) -> SS
Use with care! Same as
self.to_subset but without any property checks. Always succeeds.source§fn from_subset(element: &SS) -> SP
fn from_subset(element: &SS) -> SP
The inclusion map: converts
self to the equivalent element of its superset.source§impl<T> Tap for T
impl<T> Tap for T
source§fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Selfwhere
Self: Borrow<B>,
B: ?Sized,
fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Selfwhere
Self: Borrow<B>,
B: ?Sized,
Immutable access to the
Borrow<B> of a value. Read moresource§fn tap_borrow_mut<B>(self, func: impl FnOnce(&mut B)) -> Selfwhere
Self: BorrowMut<B>,
B: ?Sized,
fn tap_borrow_mut<B>(self, func: impl FnOnce(&mut B)) -> Selfwhere
Self: BorrowMut<B>,
B: ?Sized,
Mutable access to the
BorrowMut<B> of a value. Read moresource§fn tap_ref<R>(self, func: impl FnOnce(&R)) -> Selfwhere
Self: AsRef<R>,
R: ?Sized,
fn tap_ref<R>(self, func: impl FnOnce(&R)) -> Selfwhere
Self: AsRef<R>,
R: ?Sized,
Immutable access to the
AsRef<R> view of a value. Read moresource§fn tap_ref_mut<R>(self, func: impl FnOnce(&mut R)) -> Selfwhere
Self: AsMut<R>,
R: ?Sized,
fn tap_ref_mut<R>(self, func: impl FnOnce(&mut R)) -> Selfwhere
Self: AsMut<R>,
R: ?Sized,
Mutable access to the
AsMut<R> view of a value. Read moresource§fn tap_deref<T>(self, func: impl FnOnce(&T)) -> Selfwhere
Self: Deref<Target = T>,
T: ?Sized,
fn tap_deref<T>(self, func: impl FnOnce(&T)) -> Selfwhere
Self: Deref<Target = T>,
T: ?Sized,
Immutable access to the
Deref::Target of a value. Read moresource§fn tap_deref_mut<T>(self, func: impl FnOnce(&mut T)) -> Selfwhere
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
fn tap_deref_mut<T>(self, func: impl FnOnce(&mut T)) -> Selfwhere
Self: DerefMut<Target = T> + Deref,
T: ?Sized,
Mutable access to the
Deref::Target of a value. Read moresource§fn tap_dbg(self, func: impl FnOnce(&Self)) -> Self
fn tap_dbg(self, func: impl FnOnce(&Self)) -> Self
Calls
.tap() only in debug builds, and is erased in release builds.source§fn tap_mut_dbg(self, func: impl FnOnce(&mut Self)) -> Self
fn tap_mut_dbg(self, func: impl FnOnce(&mut Self)) -> Self
Calls
.tap_mut() only in debug builds, and is erased in release
builds. Read moresource§fn tap_borrow_dbg<B>(self, func: impl FnOnce(&B)) -> Selfwhere
Self: Borrow<B>,
B: ?Sized,
fn tap_borrow_dbg<B>(self, func: impl FnOnce(&B)) -> Selfwhere
Self: Borrow<B>,
B: ?Sized,
Calls
.tap_borrow() only in debug builds, and is erased in release
builds. Read moresource§fn tap_borrow_mut_dbg<B>(self, func: impl FnOnce(&mut B)) -> Selfwhere
Self: BorrowMut<B>,
B: ?Sized,
fn tap_borrow_mut_dbg<B>(self, func: impl FnOnce(&mut B)) -> Selfwhere
Self: BorrowMut<B>,
B: ?Sized,
Calls
.tap_borrow_mut() only in debug builds, and is erased in release
builds. Read moresource§fn tap_ref_dbg<R>(self, func: impl FnOnce(&R)) -> Selfwhere
Self: AsRef<R>,
R: ?Sized,
fn tap_ref_dbg<R>(self, func: impl FnOnce(&R)) -> Selfwhere
Self: AsRef<R>,
R: ?Sized,
Calls
.tap_ref() only in debug builds, and is erased in release
builds. Read moresource§fn tap_ref_mut_dbg<R>(self, func: impl FnOnce(&mut R)) -> Selfwhere
Self: AsMut<R>,
R: ?Sized,
fn tap_ref_mut_dbg<R>(self, func: impl FnOnce(&mut R)) -> Selfwhere
Self: AsMut<R>,
R: ?Sized,
Calls
.tap_ref_mut() only in debug builds, and is erased in release
builds. Read moresource§impl<S, T> UncheckedInto<T> for Swhere
T: UncheckedFrom<S>,
impl<S, T> UncheckedInto<T> for Swhere
T: UncheckedFrom<S>,
source§fn unchecked_into(self) -> T
fn unchecked_into(self) -> T
The counterpart to
unchecked_from.source§impl<T, S> UniqueSaturatedInto<T> for Swhere
T: Bounded,
S: TryInto<T>,
impl<T, S> UniqueSaturatedInto<T> for Swhere
T: Bounded,
S: TryInto<T>,
source§fn unique_saturated_into(self) -> T
fn unique_saturated_into(self) -> T
Consume self to return an equivalent value of
T.