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Refactor faand and flaand
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@kisakishy
kisakishy committed Oct 31, 2024
1 parent e427a70 commit 6a8bb69
Showing 1 changed file with 36 additions and 75 deletions.
111 changes: 36 additions & 75 deletions src/faand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -377,13 +377,10 @@ async fn fhaand(
for ll in 0..l {
let sj: bool = random();
let (_, kixj) = xshares[ll].1 .0[j];
let hash_kixj: [u8; 32] = blake3::hash(&kixj.0.to_le_bytes()).into();
let lsb0 = (hash_kixj[31] & 0b0000_0001) != 0;
h0h1[ll].0 = lsb0 ^ sj;

let hash_kixj_delta: [u8; 32] = blake3::hash(&(kixj.0 ^ delta.0).to_le_bytes()).into();
let lsb1 = (hash_kixj_delta[31] & 0b0000_0001) != 0;
h0h1[ll].1 = lsb1 ^ sj ^ yi[ll];
let hash_kixj = blake3::hash(&kixj.0.to_le_bytes());
let hash_kixj_delta = blake3::hash(&(kixj.0 ^ delta.0).to_le_bytes());
h0h1[ll].0 = (hash_kixj.as_bytes()[31] & 1 != 0) ^ sj;
h0h1[ll].1 = (hash_kixj_delta.as_bytes()[31] & 1 != 0) ^ sj ^ yi[ll];
vi[ll] ^= sj;
}
send_to(channel, j, "haand", &h0h1).await?;
Expand All @@ -393,13 +390,13 @@ async fn fhaand(
let h0h1_j = recv_vec_from::<(bool, bool)>(channel, j, "haand", l).await?;
for ll in 0..l {
let (mixj, _) = xshares[ll].1 .0[j];
let hash_mixj: [u8; 32] = blake3::hash(&mixj.0.to_le_bytes()).into();
let mut t = (hash_mixj[31] & 0b0000_0001) != 0;
if xshares[ll].0 {
t ^= h0h1_j[ll].1;
let hash_mixj = blake3::hash(&mixj.0.to_le_bytes());
let mut t = hash_mixj.as_bytes()[31] & 1 != 0;
t ^= if xshares[ll].0 {
h0h1_j[ll].1
} else {
t ^= h0h1_j[ll].0;
}
h0h1_j[ll].0
};
vi[ll] ^= t;
}
}
Expand All @@ -415,12 +412,8 @@ async fn fhaand(
/// with u128s instead while still cancelling the hashes out if correct.
fn hash128(input: u128) -> u128 {
let res: [u8; 32] = blake3::hash(&input.to_le_bytes()).into();
let mut value1: u128 = 0;
let mut value2: u128 = 0;
for i in 0..16 {
value1 |= (res[i] as u128) << (8 * i);
value2 |= (res[i + 16] as u128) << (8 * i);
}
let value1 = u128::from_le_bytes(res[0..16].try_into().unwrap());
let value2 = u128::from_le_bytes(res[16..32].try_into().unwrap());
value1 ^ value2
}

Expand All @@ -436,7 +429,7 @@ async fn flaand(
l: usize,
) -> Result<Vec<Share>, Error> {
// Triple computation.
// Step 1) Triple computation (inputs).
// Step 1) Triple computation [random authenticated shares as input parameters xshares, yshares, rshares].

// Step 2) Run Pi_HaAND to get back some v.
let y = yshares.iter().take(l).map(|share| share.0).collect();
Expand All @@ -445,16 +438,12 @@ async fn flaand(
// Step 3) Compute z and e AND shares.
let mut z = vec![false; l];
let mut e = vec![false; l];
let mut zshares = vec![Share(false, Auth(smallvec![(Mac(0), Key(0)); n])); l];

for ll in 0..l {
z[ll] = v[ll] ^ (xshares[ll].0 & yshares[ll].0);
e[ll] = z[ll] ^ rshares[ll].0;
}
let mut zshares = vec![Share(false, Auth(smallvec![(Mac(0), Key(0)); n])); l];
for ll in 0..l {
zshares[ll].0 = z[ll];
for k in (0..n).filter(|k| *k != i) {
zshares[ll].1 .0[k] = rshares[ll].1 .0[k];
}
}
drop(v);
drop(z);
Expand Down Expand Up @@ -489,10 +478,8 @@ async fn flaand(
let (mi_xj, _) = xshares[ll].1 .0[j];
ki_xj_phi[j][ll] ^= hash128(mi_xj.0) ^ (xbit.0 as u128 * ei_uij_k[ll].1);
// mi_xj_phi added here
}
for ll in 0..ei_uij_k.len() {
let (mac, key) = rshares[ll].1 .0[j];
// Part of Step 3) If e is true, this is negation of r as described in WRK17b, if e is false, this is a copy.
let (mac, key) = rshares[ll].1 .0[j];
if ei_uij_k[ll].0 {
zshares[ll].1 .0[j] = (mac, Key(key.0 ^ delta.0));
} else {
Expand All @@ -503,46 +490,35 @@ async fn flaand(

// Step 6) Compute hash and comm and send to all parties.
let mut hi = vec![0; l];
{
let mut commhi = Vec::with_capacity(l);
for ll in 0..l {
for k in (0..n).filter(|k| *k != i) {
let (mk_zi, ki_zk) = zshares[ll].1 .0[k];
hi[ll] ^= mk_zi.0 ^ ki_zk.0 ^ ki_xj_phi[k][ll];
}
hi[ll] ^= xshares[ll].0 as u128 * phi[ll];
hi[ll] ^= zshares[ll].0 as u128 * delta.0;
commhi.push(commit(&hi[ll].to_be_bytes()));
}
let mut commhi = Vec::with_capacity(l);
for ll in 0..l {
for k in (0..n).filter(|k| *k != i) {
send_to(channel, k, "flaand comm", &commhi).await?;
let (mk_zi, ki_zk) = zshares[ll].1 .0[k];
hi[ll] ^= mk_zi.0 ^ ki_zk.0 ^ ki_xj_phi[k][ll];
}
hi[ll] ^= (xshares[ll].0 as u128 * phi[ll]) ^ (zshares[ll].0 as u128 * delta.0);
commhi.push(commit(&hi[ll].to_be_bytes()));
}
drop(phi);
drop(ki_xj_phi);

let mut commhi_k = Vec::with_capacity(n);
for k in 0..n {
if k == i {
commhi_k.push(vec![]);
} else {
commhi_k.push(recv_vec_from::<Commitment>(channel, k, "flaand comm", l).await?);
}
// All parties first broadcast the commitment of Hi.
for k in (0..n).filter(|k| *k != i) {
send_to(channel, k, "flaand comm", &commhi).await?;
}
let mut commhi_k: Vec<Vec<Commitment>> = vec![vec![]; n];
for k in (0..n).filter(|k| *k != i) {
commhi_k[k] = recv_vec_from::<Commitment>(channel, k, "flaand comm", l).await?;
}

// Then all parties broadcast Hi.
for k in (0..n).filter(|k| *k != i) {
send_to(channel, k, "flaand hash", &hi).await?;
}

let mut xor_all_hi = hi; // XOR for all parties, including p_own
for k in (0..n).filter(|k| *k != i) {
let hi_k = recv_vec_from::<u128>(channel, k, "flaand hash", l).await?;
for (ll, (xh, hi_k)) in xor_all_hi
.iter_mut()
.zip(hi_k.into_iter())
.enumerate()
.take(l)
{
for (ll, (xh, hi_k)) in xor_all_hi.iter_mut().zip(hi_k).enumerate() {
if !open_commitment(&commhi_k[k][ll], &hi_k.to_be_bytes()) {
return Err(Error::CommitmentCouldNotBeOpened);
}
Expand All @@ -551,12 +527,9 @@ async fn flaand(
}

// Step 7) Check that the xor of all his is zero.
for xh in xor_all_hi.iter().take(l) {
if *xh != 0 {
return Err(Error::LaANDXorNotZero);
}
if xor_all_hi.iter().take(l).any(|&xh| xh != 0) {
return Err(Error::LaANDXorNotZero);
}

Ok(zshares)
}

Expand All @@ -569,20 +542,6 @@ pub(crate) fn bucket_size(circuit_size: usize) -> usize {
}
}

/// Transforms all triples into a single vector of triples.
fn transform<'a>(
x: &'a [Share],
y: &'a [Share],
z: &'a [Share],
length: usize,
) -> Vec<(&'a Share, &'a Share, &'a Share)> {
let mut triples = Vec::with_capacity(length);
for l in 0..length {
triples.push((&x[l], &y[l], &z[l]));
}
triples
}

type Bucket<'a> = SmallVec<[(&'a Share, &'a Share, &'a Share); 3]>;

/// Protocol Pi_aAND that performs F_aAND.
Expand All @@ -604,7 +563,9 @@ async fn faand(

// Step 1) Generate all leaky AND triples.
let zshares = flaand((channel, delta), (xshares, yshares, rshares), i, n, lprime).await?;
let triples = transform(xshares, yshares, &zshares, lprime);
let triples: Vec<(&Share, &Share, &Share)> = (0..lprime)
.map(|l| (&xshares[l], &yshares[l], &zshares[l]))
.collect();

// Step 2) Randomly partition all objects into l buckets, each with b objects.
let mut buckets: Vec<Bucket> = vec![smallvec![]; l];
Expand Down

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