Struct FieldElement 

pub struct FieldElement(/* private fields */);

Represents an element of the field used in the World ID Protocol (Fq), which is the BabyJubJub base field.

Note the base field of BabyJubJub is the scalar field of the BN254 curve.

This wrapper ensures consistent serialization and deserialization of field elements, where string-based serialization is done with hex encoding and binary serialization is done with byte vectors.

Implementations

impl FieldElement

pub const ZERO: Self

The additive identity of the field.

pub const ONE: Self

The multiplicative identity of the field.

pub fn to_be_bytes(&self) -> [u8; 32]

Returns the 32-byte big-endian representation of this field element.

pub fn from_be_bytes(be_bytes: &[u8; 32]) -> Result<Self, PrimitiveError>

Constructs a field element from a 32-byte big-endian representation.

Unlike from_be_bytes_mod_order, this rejects values >= the field modulus.

Errors

Returns PrimitiveError::NotInField if the value is >= the field modulus.

pub fn from_arbitrary_raw_bytes(bytes: &[u8]) -> Self

Takes arbitrary raw bytes, hashes them with a byte-friendly gas-efficient hash function and reduces it to a field element. Particularly useful for EVM on-chain use.

pub fn random<R: CryptoRng + RngCore>(rng: &mut R) -> Self

Generates a random field element using the system’s CSPRNG.

pub fn to_u256(&self) -> U256

Converts the field element to a U256.

Trait Implementations

impl Clone for FieldElement

fn clone(&self) -> FieldElement

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for FieldElement

impl Debug for FieldElement

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

Formats the value using the given formatter.

impl Default for FieldElement

fn default() -> FieldElement

Returns the “default value” for a type.

impl Deref for FieldElement

type Target = Fp<MontBackend<FrConfig, 4>, 4>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl DerefMut for FieldElement

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<'de> Deserialize<'de> for FieldElement

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for FieldElement

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

Formats the value using the given formatter.

impl Eq for FieldElement

impl From<FieldElement> for Nullifier

fn from(value: FieldElement) -> Self

Converts to this type from the input type.

impl From<FieldElement> for U256

fn from(value: FieldElement) -> Self

Converts to this type from the input type.

impl From<Fp<MontBackend<FrConfig, 4>, 4>> for FieldElement

fn from(value: Fq) -> Self

Converts to this type from the input type.

impl From<Nullifier> for FieldElement

fn from(value: Nullifier) -> Self

Converts to this type from the input type.

impl From<RpId> for FieldElement

fn from(value: RpId) -> Self

Converts to this type from the input type.

impl From<Uint<160, 3>> for FieldElement

fn from(value: U160) -> Self

Converts to this type from the input type.

impl From<u64> for FieldElement

fn from(value: u64) -> Self

Converts to this type from the input type.

impl From<u128> for FieldElement

fn from(value: u128) -> Self

Converts to this type from the input type.

impl FromStr for FieldElement

fn from_str(s: &str) -> Result<Self, Self::Err>

Parses a field element from a hex string (with optional “0x” prefix).

The value must be lower than the modulus and specifically for string encoding, proper padding is enforced (strictly 32 bytes). This is because some values in the Protocol are meant to be enforced uniqueness with, and this reduces the possibility of accidental string non-collisions.

type Err = PrimitiveError

The associated error which can be returned from parsing.

impl Hash for FieldElement

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl OprfPrefixedFieldElement for FieldElement

fn random_with_prefix<R: CryptoRng + RngCore>( rng: &mut R, prefix: OprfPrefix, ) -> FieldElement

Generate a randomized field element carrying the given OPRF prefix.

fn has_prefix(&self, prefix: OprfPrefix) -> bool

Returns whether the field element carries the given OPRF prefix.

impl Ord for FieldElement

fn cmp(&self, other: &FieldElement) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to)

Restrict a value to a certain range.

impl PartialEq for FieldElement

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for FieldElement

fn partial_cmp(&self, other: &FieldElement) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for FieldElement

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for FieldElement

impl TryFrom<FieldElement> for u64

type Error = PrimitiveError

The type returned in the event of a conversion error.

fn try_from(value: FieldElement) -> Result<Self, Self::Error>

Performs the conversion.

impl TryFrom<FieldElement> for usize

type Error = PrimitiveError

The type returned in the event of a conversion error.

fn try_from(value: FieldElement) -> Result<Self, Self::Error>

Performs the conversion.

impl TryFrom<Uint<256, 4>> for FieldElement

type Error = PrimitiveError

The type returned in the event of a conversion error.

fn try_from(value: U256) -> Result<Self, Self::Error>

Performs the conversion.