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zsa-note-encryption: introduce AssetType and encode and decode it in note plaintexts

This commit is contained in:
Aurélien Nicolas 2022-05-23 16:52:18 +02:00
parent 0d7ecad8e9
commit 96442412af
6 changed files with 138 additions and 23 deletions
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4
src/builder.rs
View File

@ -23,6 +23,7 @@ use crate::{
tree::{Anchor, MerklePath},
value::{self, NoteValue, OverflowError, ValueCommitTrapdoor, ValueCommitment, ValueSum},
};
use crate::note::AssetType;
const MIN_ACTIONS: usize = 2;
@ -150,8 +151,9 @@ impl ActionInfo {
let ak: SpendValidatingKey = self.spend.fvk.clone().into();
let alpha = pallas::Scalar::random(&mut rng);
let rk = ak.randomize(&alpha);
let asset_type = self.spend.note.asset_type();
let note = Note::new(self.output.recipient, self.output.value, nf_old, &mut rng);
let note = Note::new(self.output.recipient, self.output.value, nf_old, &mut rng, asset_type);
let cm_new = note.commitment();
let cmx = cm_new.into();

3
src/constants/fixed_bases.rs
View File

@ -30,6 +30,9 @@ pub const VALUE_COMMITMENT_R_BYTES: [u8; 1] = *b"r";
/// SWU hash-to-curve personalization for the note commitment generator
pub const NOTE_COMMITMENT_PERSONALIZATION: &str = "z.cash:Orchard-NoteCommit";
/// SWU hash-to-curve personalization for the ZSA note commitment generator
pub const NOTE_ZSA_COMMITMENT_PERSONALIZATION: &str = "z.cash:ZSA-NoteCommit";
/// SWU hash-to-curve personalization for the IVK commitment generator
pub const COMMIT_IVK_PERSONALIZATION: &str = "z.cash:Orchard-CommitIvk";

2
src/keys.rs
View File

@ -967,6 +967,7 @@ mod tests {
value::NoteValue,
Note,
};
use crate::note::AssetType;
#[test]
fn spend_validating_key_from_bytes() {
@ -1049,6 +1050,7 @@ mod tests {
NoteValue::from_raw(tv.note_v),
rho,
RandomSeed::from_bytes(tv.note_rseed, &rho).unwrap(),
AssetType::ZEC,
);
let cmx: ExtractedNoteCommitment = note.commitment().into();

40
src/note.rs
View File

@ -79,6 +79,28 @@ impl RandomSeed {
}
}
/// The ID of ZEC or a ZSA asset.
#[derive(Debug, Copy, Clone)]
pub enum AssetType {
/// Represents the native asset of the protocol, a.k.a. ZEC.
ZEC,
/// Represents a user-defined asset.
// TODO: check the uniqueness of the encoding.
Asset(ZSAType),
}
impl AssetType {
/// Parse the encoding of a ZSA asset type.
pub fn from_bytes(bytes: &[u8; 32]) -> CtOption<Self> {
pallas::Affine::from_bytes(bytes)
.map(|t| AssetType::Asset(ZSAType(t)))
}
}
/// The ID of a ZSA asset. This type cannot represent native ZEC.
#[derive(Debug, Copy, Clone)]
pub struct ZSAType(pub(crate) pallas::Affine);
/// A discrete amount of funds received by an address.
#[derive(Debug, Copy, Clone)]
pub struct Note {
@ -95,6 +117,9 @@ pub struct Note {
rho: Nullifier,
/// The seed randomness for various note components.
rseed: RandomSeed,
// TODO: merge with the value field to make it impossible to ignore?
// TODO: use a constant-time structure (like CtOption)?
asset_type: AssetType,
}
impl PartialEq for Note {
@ -113,12 +138,14 @@ impl Note {
value: NoteValue,
rho: Nullifier,
rseed: RandomSeed,
asset_type: AssetType,
) -> Self {
Note {
recipient,
value,
rho,
rseed,
asset_type,
}
}
@ -132,6 +159,7 @@ impl Note {
value: NoteValue,
rho: Nullifier,
mut rng: impl RngCore,
asset_type: AssetType,
) -> Self {
loop {
let note = Note {
@ -139,6 +167,7 @@ impl Note {
value,
rho,
rseed: RandomSeed::random(&mut rng, &rho),
asset_type,
};
if note.commitment_inner().is_some().into() {
break note;
@ -158,12 +187,14 @@ impl Note {
let sk = SpendingKey::random(rng);
let fvk: FullViewingKey = (&sk).into();
let recipient = fvk.address_at(0u32, Scope::External);
let asset_type = AssetType::ZEC;
let note = Note::new(
recipient,
NoteValue::zero(),
rho.unwrap_or_else(|| Nullifier::dummy(rng)),
rng,
asset_type,
);
(sk, fvk, note)
@ -179,6 +210,11 @@ impl Note {
self.value
}
/// Returns the asset type of this note.
pub fn asset_type(&self) -> AssetType {
self.asset_type
}
/// Returns the rseed value of this note.
pub(crate) fn rseed(&self) -> &RandomSeed {
&self.rseed
@ -223,6 +259,7 @@ impl Note {
self.rho.0,
self.rseed.psi(&self.rho),
self.rseed.rcm(&self.rho),
self.asset_type,
)
}
@ -269,7 +306,7 @@ pub mod testing {
address::testing::arb_address, note::nullifier::testing::arb_nullifier, value::NoteValue,
};
use super::{Note, RandomSeed};
use super::{AssetType, Note, RandomSeed};
prop_compose! {
/// Generate an arbitrary random seed
@ -290,6 +327,7 @@ pub mod testing {
value,
rho,
rseed,
asset_type: AssetType::ZEC,
}
}
}

58
src/note/commitment.rs
View File

@ -11,6 +11,9 @@ use crate::{
spec::extract_p,
value::NoteValue,
};
use crate::note::AssetType;
use group::GroupEncoding;
use crate::constants::fixed_bases::NOTE_ZSA_COMMITMENT_PERSONALIZATION;
#[derive(Clone, Debug)]
pub(crate) struct NoteCommitTrapdoor(pub(super) pallas::Scalar);
@ -44,16 +47,57 @@ impl NoteCommitment {
rho: pallas::Base,
psi: pallas::Base,
rcm: NoteCommitTrapdoor,
asset_type: AssetType,
) -> CtOption<Self> {
let domain = sinsemilla::CommitDomain::new(NOTE_COMMITMENT_PERSONALIZATION);
let g_d_bits = BitArray::<_, Lsb0>::new(g_d);
let pk_d_bits = BitArray::<_, Lsb0>::new(pk_d);
let v_bits = v.to_le_bits();
let rho_bits = rho.to_le_bits();
let psi_bits = psi.to_le_bits();
let zec_note_bits = iter::empty()
.chain(g_d_bits.iter().by_vals())
.chain(pk_d_bits.iter().by_vals())
.chain(v_bits.iter().by_vals())
.chain(rho_bits.iter().by_vals().take(L_ORCHARD_BASE))
.chain(psi_bits.iter().by_vals().take(L_ORCHARD_BASE));
// TODO: make this match constant-time.
match asset_type {
// Commit to ZEC notes as per the Orchard protocol.
AssetType::ZEC =>
Self::commit(
NOTE_COMMITMENT_PERSONALIZATION,
zec_note_bits,
rcm,
),
// Commit to non-ZEC notes as per the ZSA protocol.
AssetType::Asset(zsa_type) => {
// Append the asset type to the Orchard note encoding.
let encoded_type = BitArray::<_, Lsb0>::new(zsa_type.0.to_bytes());
let zsa_note_bits = zec_note_bits
.chain(encoded_type.iter().by_vals());
// Commit in a different domain than Orchard notes.
Self::commit(
NOTE_ZSA_COMMITMENT_PERSONALIZATION,
zsa_note_bits,
rcm,
)
},
}
}
fn commit(
personalization: &str,
bits: impl Iterator<Item = bool>,
rcm: NoteCommitTrapdoor,
) -> CtOption<Self> {
let domain = sinsemilla::CommitDomain::new(personalization);
domain
.commit(
iter::empty()
.chain(BitArray::<_, Lsb0>::new(g_d).iter().by_vals())
.chain(BitArray::<_, Lsb0>::new(pk_d).iter().by_vals())
.chain(v.to_le_bits().iter().by_vals())
.chain(rho.to_le_bits().iter().by_vals().take(L_ORCHARD_BASE))
.chain(psi.to_le_bits().iter().by_vals().take(L_ORCHARD_BASE)),
bits,
&rcm.0,
)
.map(NoteCommitment)

54
src/note_encryption.rs
View File

@ -4,11 +4,7 @@ use core::fmt;
use blake2b_simd::{Hash, Params};
use group::ff::PrimeField;
use zcash_note_encryption::{
BatchDomain, Domain, EphemeralKeyBytes, NotePlaintextBytes, OutPlaintextBytes,
OutgoingCipherKey, ShieldedOutput, COMPACT_NOTE_SIZE, ENC_CIPHERTEXT_SIZE, NOTE_PLAINTEXT_SIZE,
OUT_PLAINTEXT_SIZE,
};
use zcash_note_encryption::{BatchDomain, Domain, EphemeralKeyBytes, NotePlaintextBytes, OutPlaintextBytes, OutgoingCipherKey, ShieldedOutput, COMPACT_NOTE_SIZE, COMPACT_ZSA_NOTE_SIZE, ENC_CIPHERTEXT_SIZE, NOTE_PLAINTEXT_SIZE, OUT_PLAINTEXT_SIZE, MEMO_SIZE};
use crate::{
action::Action,
@ -21,6 +17,9 @@ use crate::{
value::{NoteValue, ValueCommitment},
Address, Note,
};
use crate::note::AssetType;
use group::GroupEncoding;
use subtle::CtOption;
const PRF_OCK_ORCHARD_PERSONALIZATION: &[u8; 16] = b"Zcash_Orchardock";
@ -57,12 +56,11 @@ fn orchard_parse_note_plaintext_without_memo<F>(
where
F: FnOnce(&Diversifier) -> Option<DiversifiedTransmissionKey>,
{
assert!(plaintext.len() >= COMPACT_NOTE_SIZE);
assert!(plaintext.len() >= COMPACT_NOTE_SIZE); // TODO: don’t panic, return None.
// Check note plaintext version
if plaintext[0] != 0x02 {
return None;
}
// and parse the asset type accordingly.
let asset_type = parse_version_and_asset_type(plaintext)?;
// The unwraps below are guaranteed to succeed by the assertion above
let diversifier = Diversifier::from_bytes(plaintext[1..12].try_into().unwrap());
@ -75,10 +73,23 @@ where
let pk_d = get_validated_pk_d(&diversifier)?;
let recipient = Address::from_parts(diversifier, pk_d);
let note = Note::from_parts(recipient, value, domain.rho, rseed);
let note = Note::from_parts(recipient, value, domain.rho, rseed, asset_type);
Some((note, recipient))
}
fn parse_version_and_asset_type(plaintext: &[u8]) -> Option<AssetType> {
// TODO: make this constant-time?
match plaintext[0] {
0x02 => Some(AssetType::ZEC),
0x03 if plaintext.len() >= COMPACT_ZSA_NOTE_SIZE => {
let bytes = &plaintext[COMPACT_NOTE_SIZE..COMPACT_ZSA_NOTE_SIZE].try_into().unwrap();
AssetType::from_bytes(bytes).into()
}
_ => None,
}
}
/// Orchard-specific note encryption logic.
#[derive(Debug)]
pub struct OrchardDomain {
@ -107,7 +118,7 @@ impl Domain for OrchardDomain {
type ValueCommitment = ValueCommitment;
type ExtractedCommitment = ExtractedNoteCommitment;
type ExtractedCommitmentBytes = [u8; 32];
type Memo = [u8; 512]; // TODO use a more interesting type
type Memo = [u8; MEMO_SIZE]; // TODO use a more interesting type
fn derive_esk(note: &Self::Note) -> Option<Self::EphemeralSecretKey> {
Some(note.esk())
@ -148,11 +159,24 @@ impl Domain for OrchardDomain {
memo: &Self::Memo,
) -> NotePlaintextBytes {
let mut np = [0; NOTE_PLAINTEXT_SIZE];
np[0] = 0x02;
np[0] = match note.asset_type() {
AssetType::ZEC => 0x02,
AssetType::Asset(_) => 0x03,
};
np[1..12].copy_from_slice(note.recipient().diversifier().as_array());
np[12..20].copy_from_slice(&note.value().to_bytes());
np[20..52].copy_from_slice(note.rseed().as_bytes());
np[52..].copy_from_slice(memo);
match note.asset_type() {
AssetType::ZEC => {
np[52..].copy_from_slice(memo);
},
AssetType::Asset(zsa_type) => {
np[52..84].copy_from_slice(&zsa_type.0.to_bytes());
let short_memo = &memo[0..memo.len()-32];
np[84..].copy_from_slice(short_memo);
// TODO: handle full-size memo or make short_memo explicit.
}
};
NotePlaintextBytes(np)
}
@ -327,6 +351,7 @@ mod tests {
value::{NoteValue, ValueCommitment},
Address, Note,
};
use crate::note::AssetType;
#[test]
fn test_vectors() {
@ -369,7 +394,8 @@ mod tests {
assert_eq!(ock.as_ref(), tv.ock);
let recipient = Address::from_parts(d, pk_d);
let note = Note::from_parts(recipient, value, rho, rseed);
let asset_type = AssetType::ZEC; // TODO: from data.
let note = Note::from_parts(recipient, value, rho, rseed, asset_type);
assert_eq!(ExtractedNoteCommitment::from(note.commitment()), cmx);
let action = Action::from_parts(