Struct ValueCommitment

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

A commitment to a ValueSum.

Consensus rules

The Zcash Protocol Spec requires Sapling Spend Descriptions and Output Descriptions to not contain a small order ValueCommitment. However, the ValueCommitment type as specified (and implemented here) may contain a small order point. In practice, it will not occur:

• ValueCommitment::derive will only produce a small order point if both the given NoteValue and ValueCommitTrapdoor are zero. However, the only constructor available for ValueCommitTrapdoor is ValueCommitTrapdoor::random, which will produce zero with negligible probability (assuming a non-broken PRNG).
• ValueCommitment::from_bytes_not_small_order enforces this by definition, and is the only constructor that can be used with data received over the network.

Implementations

impl ValueCommitment

pub fn derive(value: NoteValue, rcv: ValueCommitTrapdoor) -> Self

Derives a ValueCommitment by $\mathsf{ValueCommit^{Sapling}}$.

Defined in Zcash Protocol Spec § 5.4.8.3: Homomorphic Pedersen commitments (Sapling and Orchard).

pub fn as_inner(&self) -> &ExtendedPoint

Returns the inner Jubjub point representing this value commitment.

This is public for access by zcash_proofs.

pub fn from_bytes_not_small_order(bytes: &[u8; 32]) -> CtOption<ValueCommitment>

Deserializes a value commitment from its byte representation.

Returns None if bytes is an invalid representation of a Jubjub point, or the resulting point is of small order.

This method can be used to enforce the “not small order” consensus rules defined in Zcash Protocol Spec § 4.4: Spend Descriptions and § 4.5: Output Descriptions.

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

Serializes this value commitment to its canonical byte representation.

Trait Implementations

impl Add<&ValueCommitment> for CommitmentSum

type Output = CommitmentSum

The resulting type after applying the + operator.

fn add(self, rhs: &ValueCommitment) -> Self::Output

Performs the + operation.

impl Add<&ValueCommitment> for ValueCommitment

type Output = CommitmentSum

The resulting type after applying the + operator.

fn add(self, rhs: &Self) -> Self::Output

Performs the + operation.

impl AddAssign<&ValueCommitment> for CommitmentSum

fn add_assign(&mut self, rhs: &ValueCommitment)

Performs the += operation.

impl Clone for ValueCommitment

fn clone(&self) -> ValueCommitment

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for ValueCommitment

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

Formats the value using the given formatter.

impl Sub<&ValueCommitment> for ValueCommitment

type Output = CommitmentSum

The resulting type after applying the - operator.

fn sub(self, rhs: &Self) -> Self::Output

Performs the - operation.

impl SubAssign<&ValueCommitment> for CommitmentSum

fn sub_assign(&mut self, rhs: &ValueCommitment)

Performs the -= operation.

impl<'a> Sum<&'a ValueCommitment> for CommitmentSum

fn sum<I: Iterator<Item = &'a ValueCommitment>>(iter: I) -> Self

Takes an iterator and generates Self from the elements by “summing up” the items.

impl Sum<ValueCommitment> for CommitmentSum

fn sum<I: Iterator<Item = ValueCommitment>>(iter: I) -> Self

Takes an iterator and generates Self from the elements by “summing up” the items.