Struct EidosRandomCoin 

pub struct EidosRandomCoin { /* private fields */ }

A reseedable random coin built from Eidos compression.

State derivation and output generation use separate Eidos domains. Output block i is the field hash of the internal state and a non-wrapping u64 counter. Reseeding replaces the state with the field hash of the current state, counter, and supplied data, discards buffered output, and resets the counter. The output path uses only Eidos field elements and is independent of the compression core’s output representation. The stored random-coin state is distinct from the temporary, domain-specific chaining value constructed by each framed Eidos hash.

This counter-mode construction does not provide backtracking resistance within a reseed interval: knowledge of the stored state permits recomputing every output block derived from that state.

Implementations

impl EidosRandomCoin

pub fn new(seed: Word) -> EidosRandomCoin

Returns a random coin initialized with seed.

pub fn from_parts( state: Word, output: Word, counter: u64, current: usize, ) -> EidosRandomCoin

Returns a random coin reconstructed from its serialized components.

counter is the index of the next output block and therefore the number of blocks generated since initialization or the most recent reseed. If current is less than four, output is the block at counter - 1, and current identifies its next candidate Felt. A value of four means that the buffer is exhausted. This constructor trusts output; it does not recompute the buffered block.

Panics

Panics if current is greater than the number of buffered output elements, or if buffered output is supplied before any output block has been generated.

pub fn into_parts(self) -> (Word, Word, u64, usize)

Returns (state, output, counter, current).

counter is the index of the next output block, and current is the next candidate Felt in output. A current value equal to four marks an exhausted buffer.

pub fn fill_bytes(&mut self, dest: &mut [u8])

Fills dest with random bytes.

Panics

Panics if output generation requires another block after the u64 block counter is exhausted.

pub fn draw_basefield(&mut self) -> Felt

Draws a uniformly distributed base-field element.

Panics

Panics if output generation requires another block after the u64 block counter is exhausted.

pub fn draw(&mut self) -> Felt

Draws a uniformly distributed base-field element.

Panics

Panics under the same condition as Self::draw_basefield.

pub fn draw_ext_field<E>(&mut self) -> E

where E: ExtensionField<Felt>,

Draws a uniformly distributed extension-field element.

Panics

Panics under the same condition as Self::draw_basefield.

pub fn reseed(&mut self, data: Word)

Mixes four additional field elements into the random-coin state.

The current output-block counter is bound into the new state. Any buffered output is discarded, and the block counter is reset to zero.

Trait Implementations

impl Clone for EidosRandomCoin

fn clone(&self) -> EidosRandomCoin

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for EidosRandomCoin

impl Debug for EidosRandomCoin

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Deserializable for EidosRandomCoin

fn read_from<R>(source: &mut R) -> Result<EidosRandomCoin, DeserializationError>

where R: ByteReader,

Reads a sequence of bytes from the provided source, attempts to deserialize these bytes into Self, and returns the result.

fn min_serialized_size() -> usize

Returns the minimum serialized size for one instance of this type.

fn read_from_bytes(bytes: &[u8]) -> Result<Self, DeserializationError>

Attempts to deserialize the provided bytes into Self and returns the result.

fn read_from_bytes_with_budget( bytes: &[u8], budget: usize, ) -> Result<Self, DeserializationError>

Deserializes Self from bytes with a byte budget limit.

impl Eq for EidosRandomCoin

impl FeltRng for EidosRandomCoin

fn draw_element(&mut self) -> Felt

Draw, uniformly at random, a base field element.

fn draw_word(&mut self) -> Word

Draw, uniformly at random, a Word.

impl PartialEq for EidosRandomCoin

fn eq(&self, other: &EidosRandomCoin) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serializable for EidosRandomCoin

fn write_into<W>(&self, target: &mut W)

where W: ByteWriter,

Serializes self into bytes and writes these bytes into the target.

fn to_bytes(&self) -> Vec<u8>

Serializes self into a vector of bytes.

fn get_size_hint(&self) -> usize

Returns an estimate of how many bytes are needed to represent self.

impl StructuralPartialEq for EidosRandomCoin

impl TryRng for EidosRandomCoin

type Error = !

The type returned in the event of a RNG error.

fn try_next_u32(&mut self) -> Result<u32, <EidosRandomCoin as TryRng>::Error>

Return the next random u32.

fn try_next_u64(&mut self) -> Result<u64, <EidosRandomCoin as TryRng>::Error>

Return the next random u64.

fn try_fill_bytes( &mut self, dest: &mut [u8], ) -> Result<(), <EidosRandomCoin as TryRng>::Error>

Fill dst entirely with random data.