Struct Nullifier 

pub struct Nullifier {
    pub inner: FieldElement,
}

A nullifier is a unique, one-time identifier derived from (user, rpId, action) that lets RPs detect duplicate actions without learning who the user is. Used with the contract’s verify() function.

Internally, this is a thin wrapper to identify explicitly a single nullifier. This wrapper is used to expose explicit canonical serialization which is critical for uniqueness.

Fields

inner: FieldElement

The FieldElement representing the nullifier.

Implementations

impl Nullifier

pub const fn new(nullifier: FieldElement) -> Self

Initializes a new Nullifier from a FieldElement

pub fn as_number(&self) -> U256

Outputs the nullifier as a number. This is the recommended way of enforcing nullifier uniqueness.

Store this number directly to enforce uniqueness.

pub fn to_canonical_string(&self) -> String

Serializes a nullifier in a canonical string representation.

It is generally safe to do uniqueness on nullifiers treating them as strings if you always serialize them with this method. However, storing nullifiers as numbers instead is recommended.

Warning

Using a canonical representation is particularly important for nullifiers. Otherwise, different strings may actually represent the same field elements, which could result in a compromise of uniqueness.

Details

In particular, this method adds an explicit prefix, serializes the field element to a 32-byte hex padded string with only lowercase characters.

pub fn from_canonical_string(nullifier: String) -> Result<Self, PrimitiveError>

Deserializes a nullifier from a canonical string representation. In particular, this method will enforce all the required rules to ensure the value was canonically serialized.

For example, the following string representations are equivalently the same field element: 0xa, 0xA, 0x0A, this method will ensure a single representation exists for each field element.

Errors

Will return an error if any of the encoding conditions failed (e.g. invalid characters, invalid length, etc.)

Methods from Deref<Target = FieldElement>

pub const ZERO: Self

pub const ONE: Self

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

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

pub fn to_u256(&self) -> U256

Converts the field element to a U256.

Trait Implementations

impl Clone for Nullifier

fn clone(&self) -> Nullifier

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Nullifier

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

Formats the value using the given formatter.

impl Deref for Nullifier

type Target = FieldElement

The resulting type after dereferencing.

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

Dereferences the value.

impl<'de> Deserialize<'de> for Nullifier

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

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for Nullifier

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

Formats the value using the given formatter.

impl From<FieldElement> for Nullifier

fn from(value: FieldElement) -> Self

Converts to this type from the input type.

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

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<Nullifier> for U256

fn from(value: Nullifier) -> Self

Converts to this type from the input type.

impl Hash for Nullifier

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 PartialEq for Nullifier

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Nullifier

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

where S: Serializer,

Serialize this value into the given Serde serializer.

impl Copy for Nullifier

impl Eq for Nullifier

impl StructuralPartialEq for Nullifier