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adds test for linear relation between pedersen hash generators

This commit is contained in:
Kobi Gurkan 2018-08-01 09:26:30 +03:00 committed by Jack Grigg
parent 3efb7f9146
commit 15b4c37ab0
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GPG Key ID: 9E8255172BBF9898
1 changed files with 112 additions and 58 deletions
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170
zcash_primitives/src/jubjub/mod.rs
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@ -216,28 +216,6 @@ impl JubjubBls12 {
fixed_base_circuit_generators: vec![],
};
fn find_group_hash<E: JubjubEngine>(
m: &[u8],
personalization: &[u8; 8],
params: &E::Params,
) -> edwards::Point<E, PrimeOrder> {
let mut tag = m.to_vec();
let i = tag.len();
tag.push(0u8);
loop {
let gh = group_hash(&tag, personalization, params);
// We don't want to overflow and start reusing generators
assert!(tag[i] != u8::max_value());
tag[i] += 1;
if let Some(gh) = gh {
break gh;
}
}
}
// Create the bases for the Pedersen hashes
{
let mut pedersen_hash_generators = vec![];
@ -250,26 +228,17 @@ impl JubjubBls12 {
.write_u32::<LittleEndian>(m)
.unwrap();
pedersen_hash_generators.push(find_group_hash(
pedersen_hash_generators.push(JubjubBls12::find_group_hash(
&segment_number,
constants::PEDERSEN_HASH_GENERATORS_PERSONALIZATION,
&tmp_params,
));
}
// Check for duplicates, far worse than spec inconsistencies!
for (i, p1) in pedersen_hash_generators.iter().enumerate() {
if p1 == &edwards::Point::zero() {
panic!("Neutral element!");
}
for p2 in pedersen_hash_generators.iter().skip(i + 1) {
if p1 == p2 {
panic!("Duplicate generator!");
}
}
}
JubjubBls12::check_consistency_of_pedersen_hash_generators(
&tmp_params,
&pedersen_hash_generators,
);
tmp_params.pedersen_hash_generators = pedersen_hash_generators;
}
@ -314,43 +283,47 @@ impl JubjubBls12 {
let mut fixed_base_generators =
vec![edwards::Point::zero(); FixedGenerators::Max as usize];
fixed_base_generators[FixedGenerators::ProofGenerationKey as usize] = find_group_hash(
&[],
constants::PROOF_GENERATION_KEY_BASE_GENERATOR_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::ProofGenerationKey as usize] =
JubjubBls12::find_group_hash(
&[],
constants::PROOF_GENERATION_KEY_BASE_GENERATOR_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::NoteCommitmentRandomness as usize] =
find_group_hash(
JubjubBls12::find_group_hash(
b"r",
constants::PEDERSEN_HASH_GENERATORS_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::NullifierPosition as usize] = find_group_hash(
&[],
constants::NULLIFIER_POSITION_IN_TREE_GENERATOR_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::NullifierPosition as usize] =
JubjubBls12::find_group_hash(
&[],
constants::NULLIFIER_POSITION_IN_TREE_GENERATOR_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::ValueCommitmentValue as usize] = find_group_hash(
b"v",
constants::VALUE_COMMITMENT_GENERATOR_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::ValueCommitmentValue as usize] =
JubjubBls12::find_group_hash(
b"v",
constants::VALUE_COMMITMENT_GENERATOR_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::ValueCommitmentRandomness as usize] =
find_group_hash(
JubjubBls12::find_group_hash(
b"r",
constants::VALUE_COMMITMENT_GENERATOR_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::SpendingKeyGenerator as usize] = find_group_hash(
&[],
constants::SPENDING_KEY_GENERATOR_PERSONALIZATION,
&tmp_params,
);
fixed_base_generators[FixedGenerators::SpendingKeyGenerator as usize] =
JubjubBls12::find_group_hash(
&[],
constants::SPENDING_KEY_GENERATOR_PERSONALIZATION,
&tmp_params,
);
// Check for duplicates, far worse than spec inconsistencies!
for (i, p1) in fixed_base_generators.iter().enumerate() {
@ -427,6 +400,55 @@ impl JubjubBls12 {
tmp_params
}
fn find_group_hash<E: JubjubEngine>(
m: &[u8],
personalization: &[u8; 8],
params: &E::Params,
) -> edwards::Point<E, PrimeOrder> {
let mut tag = m.to_vec();
let i = tag.len();
tag.push(0u8);
loop {
let gh = group_hash(&tag, personalization, params);
// We don't want to overflow and start reusing generators
assert!(tag[i] != u8::max_value());
tag[i] += 1;
if let Some(gh) = gh {
break gh;
}
}
}
/// Check for simple relations between the generators, that make finding collisions easy;
/// far worse than spec inconsistencies!
fn check_consistency_of_pedersen_hash_generators<E: JubjubEngine>(
tmp_params: &E::Params,
pedersen_hash_generators: &[edwards::Point<E, PrimeOrder>],
) {
let sum = &edwards::Point::zero();
for (i, p1) in pedersen_hash_generators.iter().enumerate() {
if p1 == &edwards::Point::zero() {
panic!("Neutral element!");
}
// Used for checking no generator is a sum of previous ones.
let sum = &sum.add(&p1, &tmp_params);
for p2 in pedersen_hash_generators.iter().skip(i + 1) {
if p1 == p2 {
panic!("Duplicate generator!");
}
if p1 == &p2.negate() {
panic!("Inverse generator!");
}
if sum == p2 {
panic!("Linear relation between generators!");
}
}
}
}
}
#[test]
@ -464,3 +486,35 @@ fn test_jubjub_bls12() {
assert!(p == q);
}
#[test]
#[should_panic(expected = "Linear relation between generators!")]
fn test_jubjub_bls12_pedersen_hash_generators_consistency_check_linear_relation() {
let params = JubjubBls12::new();
let mut pedersen_hash_generators: Vec<edwards::Point<Bls12, PrimeOrder>> = vec![];
use byteorder::{LittleEndian, WriteBytesExt};
for m in 0..5 {
let mut segment_number = [0u8; 4];
(&mut segment_number[0..4])
.write_u32::<LittleEndian>(m)
.unwrap();
let p = JubjubBls12::find_group_hash(
&segment_number,
constants::PEDERSEN_HASH_GENERATORS_PERSONALIZATION,
&params,
);
pedersen_hash_generators.push(p);
}
let p1 = pedersen_hash_generators[0].clone();
let p2 = pedersen_hash_generators[1].clone();
//test for linear relation
pedersen_hash_generators.push(p1.add(&p2, &params));
JubjubBls12::check_consistency_of_pedersen_hash_generators(&params, &pedersen_hash_generators);
}