561 lines
17 KiB
Rust
561 lines
17 KiB
Rust
#[cfg(test)]
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pub mod test;
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pub mod boolean;
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pub mod uint32;
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pub mod blake2s;
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pub mod num;
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pub mod lookup;
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pub mod ecc;
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pub mod pedersen_hash;
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use pairing::{
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PrimeField,
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PrimeFieldRepr,
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};
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use bellman::{
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SynthesisError,
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ConstraintSystem,
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Circuit
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};
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use jubjub::{
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JubjubEngine,
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Unknown,
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FixedGenerators,
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edwards
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};
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trait Assignment<T> {
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fn get(&self) -> Result<&T, SynthesisError>;
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}
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impl<T> Assignment<T> for Option<T> {
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fn get(&self) -> Result<&T, SynthesisError> {
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match *self {
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Some(ref v) => Ok(v),
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None => Err(SynthesisError::AssignmentMissing)
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}
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}
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}
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pub struct Spend<'a, E: JubjubEngine> {
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pub params: &'a E::Params,
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/// Value of the note being spent
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pub value: Option<u64>,
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/// Randomness that will hide the value
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pub value_randomness: Option<E::Fs>,
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/// Key which allows the proof to be constructed
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/// as defense-in-depth against a flaw in the
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/// protocol that would otherwise be exploitable
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/// by a holder of a viewing key.
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pub rsk: Option<E::Fs>,
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/// The public key that will be re-randomized for
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/// use as a nullifier and signing key for the
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/// transaction.
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pub ak: Option<edwards::Point<E, Unknown>>,
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/// The diversified base used to compute pk_d.
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pub g_d: Option<edwards::Point<E, Unknown>>,
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/// The randomness used to hide the note commitment data
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pub commitment_randomness: Option<E::Fs>,
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/// The authentication path of the commitment in the tree
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pub auth_path: Vec<Option<(E::Fr, bool)>>
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}
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impl<'a, E: JubjubEngine> Circuit<E> for Spend<'a, E> {
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fn synthesize<CS: ConstraintSystem<E>>(self, cs: &mut CS) -> Result<(), SynthesisError>
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{
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// Booleanize the value into little-endian bit order
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let value_bits = boolean::u64_into_boolean_vec_le(
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cs.namespace(|| "value"),
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self.value
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)?;
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{
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let gv = ecc::fixed_base_multiplication(
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cs.namespace(|| "compute the value in the exponent"),
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FixedGenerators::ValueCommitmentValue,
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&value_bits,
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self.params
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)?;
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// Booleanize the randomness
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let hr = boolean::field_into_boolean_vec_le(
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cs.namespace(|| "hr"),
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self.value_randomness
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)?;
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let hr = ecc::fixed_base_multiplication(
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cs.namespace(|| "computation of randomization for value commitment"),
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FixedGenerators::ValueCommitmentRandomness,
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&hr,
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self.params
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)?;
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let gvhr = gv.add(
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cs.namespace(|| "computation of value commitment"),
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&hr,
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self.params
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)?;
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gvhr.inputize(cs.namespace(|| "value commitment"))?;
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}
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// Compute rk = [rsk] ProvingPublicKey
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let rk;
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{
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// Witness rsk as bits
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let rsk = boolean::field_into_boolean_vec_le(
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cs.namespace(|| "rsk"),
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self.rsk
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)?;
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// NB: We don't ensure that the bit representation of rsk
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// is "in the field" (Fs) because it's not used except to
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// demonstrate the prover knows it. If they know a
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// congruency then that's equivalent.
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rk = ecc::fixed_base_multiplication(
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cs.namespace(|| "computation of rk"),
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FixedGenerators::ProvingPublicKey,
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&rsk,
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self.params
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)?;
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}
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// Prover witnesses ak (ensures that it's on the curve)
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let ak = ecc::EdwardsPoint::witness(
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cs.namespace(|| "ak"),
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self.ak,
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self.params
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)?;
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ak.assert_not_small_order(
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cs.namespace(|| "ak not small order"),
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self.params
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)?;
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// Unpack ak and rk for input to BLAKE2s
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let mut vk = vec![];
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let mut rho_preimage = vec![];
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vk.extend(
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ak.repr(cs.namespace(|| "representation of ak"))?
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);
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{
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let repr_rk = rk.repr(
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cs.namespace(|| "representation of rk")
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)?;
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vk.extend(repr_rk.iter().cloned());
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rho_preimage.extend(repr_rk);
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}
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assert_eq!(vk.len(), 512);
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// Compute the incoming viewing key
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let mut ivk = blake2s::blake2s(
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cs.namespace(|| "computation of ivk"),
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&vk,
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::CRH_IVK_PERSONALIZATION
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)?;
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// Little endian bit order
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ivk.reverse();
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ivk.truncate(E::Fs::CAPACITY as usize); // drop_5
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// Witness g_d
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let g_d = ecc::EdwardsPoint::witness(
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cs.namespace(|| "witness g_d"),
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self.g_d,
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self.params
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)?;
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// Compute pk_d
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let pk_d = g_d.mul(
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cs.namespace(|| "compute pk_d"),
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&ivk,
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self.params
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)?;
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// Compute note contents
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let mut note_contents = vec![];
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note_contents.extend(value_bits.into_iter().rev());
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note_contents.extend(
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g_d.repr(cs.namespace(|| "representation of g_d"))?
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);
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note_contents.extend(
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pk_d.repr(cs.namespace(|| "representation of pk_d"))?
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);
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assert_eq!(
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note_contents.len(),
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64 + // value
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256 + // g_d
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256 // p_d
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);
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// Compute the hash of the note contents
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let mut cm = pedersen_hash::pedersen_hash(
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cs.namespace(|| "note content hash"),
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pedersen_hash::Personalization::NoteCommitment,
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¬e_contents,
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self.params
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)?;
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{
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// Booleanize the randomness
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let cmr = boolean::field_into_boolean_vec_le(
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cs.namespace(|| "cmr"),
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self.commitment_randomness
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)?;
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let cmr = ecc::fixed_base_multiplication(
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cs.namespace(|| "computation of commitment randomness"),
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FixedGenerators::NoteCommitmentRandomness,
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&cmr,
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self.params
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)?;
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cm = cm.add(
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cs.namespace(|| "randomization of note commitment"),
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&cmr,
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self.params
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)?;
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}
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let tree_depth = self.auth_path.len();
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let mut position_bits = vec![];
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// Injective encoding.
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let mut cur = cm.x.clone();
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for (i, e) in self.auth_path.into_iter().enumerate() {
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let cs = &mut cs.namespace(|| format!("merkle tree hash {}", i));
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let cur_is_right = boolean::Boolean::from(boolean::AllocatedBit::alloc(
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cs.namespace(|| "position bit"),
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e.map(|e| e.1)
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)?);
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position_bits.push(cur_is_right.clone());
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let path_element = num::AllocatedNum::alloc(
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cs.namespace(|| "path element"),
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|| {
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Ok(e.get()?.0)
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}
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)?;
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let (xl, xr) = num::AllocatedNum::conditionally_reverse(
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cs.namespace(|| "conditional reversal of preimage"),
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&cur,
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&path_element,
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&cur_is_right
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)?;
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// We don't need to be strict, because the function is
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// collision-resistant. If the prover witnesses a congruency,
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// they will be unable to find an authentication path in the
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// tree with high probability.
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let mut preimage = vec![];
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preimage.extend(xl.into_bits_le(cs.namespace(|| "xl into bits"))?);
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preimage.extend(xr.into_bits_le(cs.namespace(|| "xr into bits"))?);
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cur = pedersen_hash::pedersen_hash(
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cs.namespace(|| "computation of pedersen hash"),
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pedersen_hash::Personalization::MerkleTree(i),
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&preimage,
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self.params
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)?.x; // Injective encoding
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}
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assert_eq!(position_bits.len(), tree_depth);
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// Expose the anchor
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cur.inputize(cs.namespace(|| "anchor"))?;
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{
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let position = ecc::fixed_base_multiplication(
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cs.namespace(|| "g^position"),
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FixedGenerators::NullifierPosition,
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&position_bits,
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self.params
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)?;
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cm = cm.add(
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cs.namespace(|| "faerie gold prevention"),
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&position,
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self.params
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)?;
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}
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// Let's compute rho = BLAKE2s(rk || cm + position)
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rho_preimage.extend(
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cm.repr(cs.namespace(|| "representation of cm"))?
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);
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assert_eq!(rho_preimage.len(), 512);
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let mut rho = blake2s::blake2s(
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cs.namespace(|| "rho computation"),
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&rho_preimage,
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::PRF_NR_PERSONALIZATION
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)?;
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// Little endian bit order
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rho.reverse();
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rho.truncate(E::Fs::CAPACITY as usize); // drop_5
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// Compute nullifier
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let nf = ak.mul(
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cs.namespace(|| "computation of nf"),
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&rho,
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self.params
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)?;
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nf.inputize(cs.namespace(|| "nullifier"))?;
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Ok(())
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}
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}
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/// This is an output circuit instance.
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pub struct Output<'a, E: JubjubEngine> {
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pub params: &'a E::Params,
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/// Value of the note being created
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pub value: Option<u64>,
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/// Randomness that will hide the value
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pub value_randomness: Option<E::Fs>,
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/// The diversified base, computed by GH(d)
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pub g_d: Option<edwards::Point<E, Unknown>>,
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/// The diversified address point, computed by GH(d)^ivk
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pub p_d: Option<edwards::Point<E, Unknown>>,
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/// The randomness used to hide the note commitment data
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pub commitment_randomness: Option<E::Fs>,
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/// The ephemeral secret key for DH with recipient
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pub esk: Option<E::Fs>
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}
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impl<'a, E: JubjubEngine> Circuit<E> for Output<'a, E> {
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fn synthesize<CS: ConstraintSystem<E>>(self, cs: &mut CS) -> Result<(), SynthesisError>
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{
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// Booleanize the value into little-endian bit order
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let value_bits = boolean::u64_into_boolean_vec_le(
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cs.namespace(|| "value"),
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self.value
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)?;
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{
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let gv = ecc::fixed_base_multiplication(
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cs.namespace(|| "compute the value in the exponent"),
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FixedGenerators::ValueCommitmentValue,
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&value_bits,
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self.params
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)?;
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// Booleanize the randomness
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let hr = boolean::field_into_boolean_vec_le(
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cs.namespace(|| "hr"),
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self.value_randomness
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)?;
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let hr = ecc::fixed_base_multiplication(
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cs.namespace(|| "computation of randomization for value commitment"),
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FixedGenerators::ValueCommitmentRandomness,
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&hr,
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self.params
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)?;
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let gvhr = gv.add(
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cs.namespace(|| "computation of value commitment"),
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&hr,
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self.params
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)?;
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gvhr.inputize(cs.namespace(|| "value commitment"))?;
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}
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// Let's start to construct our note
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let mut note_contents = vec![];
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note_contents.extend(value_bits.into_iter().rev());
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// Let's deal with g_d
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{
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let g_d = ecc::EdwardsPoint::witness(
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cs.namespace(|| "witness g_d"),
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self.g_d,
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self.params
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)?;
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g_d.assert_not_small_order(
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cs.namespace(|| "g_d not small order"),
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self.params
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)?;
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note_contents.extend(
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g_d.repr(cs.namespace(|| "representation of g_d"))?
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);
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// Compute epk from esk
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let esk = boolean::field_into_boolean_vec_le(
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cs.namespace(|| "esk"),
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self.esk
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)?;
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let epk = g_d.mul(
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cs.namespace(|| "epk computation"),
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&esk,
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self.params
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)?;
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epk.inputize(cs.namespace(|| "epk"))?;
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}
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// Now let's deal with p_d. We don't do any checks and
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// essentially allow the prover to witness any 256 bits
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// they would like.
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{
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let p_d = self.p_d.map(|e| e.into_xy());
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let y_contents = boolean::field_into_boolean_vec_le(
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cs.namespace(|| "p_d bits of y"),
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p_d.map(|e| e.1)
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)?;
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let sign_bit = boolean::Boolean::from(boolean::AllocatedBit::alloc(
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cs.namespace(|| "p_d bit of x"),
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p_d.map(|e| e.0.into_repr().is_odd())
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)?);
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note_contents.extend(y_contents);
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note_contents.push(sign_bit);
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}
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assert_eq!(
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note_contents.len(),
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64 + // value
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256 + // g_d
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256 // p_d
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);
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// Compute the hash of the note contents
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let mut cm = pedersen_hash::pedersen_hash(
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cs.namespace(|| "note content hash"),
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pedersen_hash::Personalization::NoteCommitment,
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¬e_contents,
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self.params
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)?;
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{
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// Booleanize the randomness
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let cmr = boolean::field_into_boolean_vec_le(
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cs.namespace(|| "cmr"),
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self.commitment_randomness
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)?;
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let cmr = ecc::fixed_base_multiplication(
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cs.namespace(|| "computation of commitment randomness"),
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FixedGenerators::NoteCommitmentRandomness,
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&cmr,
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self.params
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)?;
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cm = cm.add(
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cs.namespace(|| "randomization of note commitment"),
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&cmr,
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self.params
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)?;
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}
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// Only the x-coordinate of the output is revealed,
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// since we know it is prime order, and we know that
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// the x-coordinate is an injective encoding for
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// prime-order elements.
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cm.x.inputize(cs.namespace(|| "commitment"))?;
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Ok(())
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}
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}
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#[test]
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fn test_input_circuit_with_bls12_381() {
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use pairing::bls12_381::*;
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use rand::{SeedableRng, Rng, XorShiftRng};
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use ::circuit::test::*;
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use jubjub::{JubjubBls12, fs};
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let params = &JubjubBls12::new();
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let rng = &mut XorShiftRng::from_seed([0x3dbe6259, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
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let tree_depth = 29;
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let value: u64 = 1;
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let value_randomness: fs::Fs = rng.gen();
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let ak: edwards::Point<Bls12, Unknown> = edwards::Point::rand(rng, params);
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let g_d: edwards::Point<Bls12, Unknown> = edwards::Point::rand(rng, params);
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let commitment_randomness: fs::Fs = rng.gen();
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let rsk: fs::Fs = rng.gen();
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let auth_path = vec![Some((rng.gen(), rng.gen())); tree_depth];
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{
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let mut cs = TestConstraintSystem::<Bls12>::new();
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let instance = Spend {
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params: params,
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value: Some(value),
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value_randomness: Some(value_randomness),
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rsk: Some(rsk),
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ak: Some(ak),
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g_d: Some(g_d),
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commitment_randomness: Some(commitment_randomness),
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auth_path: auth_path
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};
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instance.synthesize(&mut cs).unwrap();
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assert!(cs.is_satisfied());
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assert_eq!(cs.num_constraints(), 97395);
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assert_eq!(cs.hash(), "9f730803965612392772c3c1fbb110c1539656e1bab40d5a9a124b06e927ef40");
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}
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}
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#[test]
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fn test_output_circuit_with_bls12_381() {
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use pairing::bls12_381::*;
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use rand::{SeedableRng, Rng, XorShiftRng};
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use ::circuit::test::*;
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use jubjub::{JubjubBls12, fs};
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let params = &JubjubBls12::new();
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let rng = &mut XorShiftRng::from_seed([0x3dbe6258, 0x8d313d76, 0x3237db17, 0xe5bc0654]);
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let value: u64 = 1;
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let value_randomness: fs::Fs = rng.gen();
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let g_d: edwards::Point<Bls12, Unknown> = edwards::Point::rand(rng, params);
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let p_d: edwards::Point<Bls12, Unknown> = edwards::Point::rand(rng, params);
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let commitment_randomness: fs::Fs = rng.gen();
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let esk: fs::Fs = rng.gen();
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{
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let mut cs = TestConstraintSystem::<Bls12>::new();
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let instance = Output {
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params: params,
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value: Some(value),
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value_randomness: Some(value_randomness),
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g_d: Some(g_d.clone()),
|
|
p_d: Some(p_d.clone()),
|
|
commitment_randomness: Some(commitment_randomness),
|
|
esk: Some(esk.clone())
|
|
};
|
|
|
|
instance.synthesize(&mut cs).unwrap();
|
|
|
|
assert!(cs.is_satisfied());
|
|
assert_eq!(cs.num_constraints(), 7827);
|
|
assert_eq!(cs.hash(), "f4219872738a81ef3ea66199ea5019d87f53ec369ee7f64d0b7c63ade6014114");
|
|
}
|
|
}
|