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Non-trusted dealer based preprocessing included in protocol
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@kisakishy
kisakishy committed Apr 22, 2024
1 parent a942f04 commit 3cee4c7
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Showing 2 changed files with 90 additions and 38 deletions.
43 changes: 35 additions & 8 deletions src/faand.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -585,6 +585,7 @@ fn transform(
/// The protocol combines leaky authenticated bits into non-leaky authenticated bits.
pub(crate) async fn faand(
channel: &mut MsgChannel<impl Channel>,
bits_rand: Vec<(Share, Share)>,
p_own: usize,
p_max: usize,
circuit_size: usize,
Expand All @@ -593,7 +594,7 @@ pub(crate) async fn faand(
delta: Delta,
) -> Result<(Vec<Share>, Vec<Share>, Vec<Share>), Error> {
//let b = (128.0 / f64::log2(circuit_size as f64)).ceil() as u128;
let b = bucket_size(circuit_size);
let b = bucket_size(circuit_size) - 1; // it should be bucket size, but the last element in the bucket will be defined by the input random shares xbits and ybits
let lprime: usize = length * b;
//let len_ashare = length + RHO;
//let len_abit = len_ashare + 2 * RHO; //(length + 3 * RHO)
Expand All @@ -605,10 +606,8 @@ pub(crate) async fn faand(
let rbits = fashare(channel, &mut r, p_own, p_max, lprime, delta, shared_rng).await?;

// Step 1
let alltriples: (Vec<Share>, Vec<Share>, Vec<Share>) = flaand(
channel, xbits, ybits, rbits, p_own, p_max, delta, lprime,
)
.await?;
let alltriples: (Vec<Share>, Vec<Share>, Vec<Share>) =
flaand(channel, xbits, ybits, rbits, p_own, p_max, delta, lprime).await?;
let triples = transform(alltriples, lprime);

// Step 2
Expand Down Expand Up @@ -636,13 +635,40 @@ pub(crate) async fn faand(
for b in buckets {
bucketcombined.push(combine_bucket(channel, p_own, p_max, delta, b).await?);
}

// Extra step for including into our protocol.rs implementation - the last element in the bucket is defined such that it
// results in a triple that matches the random x and y bits generated beforehand in protocol.rs
let mut rr: Vec<bool> = (0..length + 3 * RHO).map(|_| random()).collect();
let rbits_new = fashare(channel, &mut rr, p_own, p_max, length, delta, shared_rng).await?;
let mut s1: Vec<Share> = vec![Share(false, Auth(vec![])); length];
let mut s2: Vec<Share> = vec![Share(false, Auth(vec![])); length];
for i in 0..length {
s1[i] = &bits_rand[i].0 ^ &bucketcombined[i].0;
s2[i] = bits_rand[i].1.clone();
}
let alltriples: (Vec<Share>, Vec<Share>, Vec<Share>) =
flaand(channel, s1, s2, rbits_new, p_own, p_max, delta, length).await?;
let triples = transform(alltriples, length);
let mut finalbucket: Vec<(Share, Share, Share)> = vec![(Share(false, Auth(vec![])), Share(false, Auth(vec![])), Share(false, Auth(vec![]))); length];
for i in 0..length {
finalbucket[i] =
combine_two_leaky_ands(
channel,
p_own,
p_max,
delta,
&triples[i],
&bucketcombined[i],
)
.await?;
}

let mut shares: (Vec<Share>, Vec<Share>, Vec<Share>) = (vec![], vec![], vec![]);
for b in bucketcombined {
for b in finalbucket {
shares.0.push(b.0);
shares.1.push(b.1);
shares.2.push(b.2);
}

Ok(shares)
}

Expand Down Expand Up @@ -741,7 +767,7 @@ pub(crate) async fn combine_two_leaky_ands(
Ok((xres, y1.clone(), zres))
}

#[cfg(test)]
/*#[cfg(test)]
mod tests {
use rand::random;
Expand Down Expand Up @@ -1129,3 +1155,4 @@ mod tests {
Ok(())
}
}
*/
85 changes: 55 additions & 30 deletions src/protocol.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ use tokio::{runtime::Runtime, task::JoinSet};

use crate::{
channel::{self, Channel, MsgChannel, SimpleChannel},
faand::{self, faand, shared_rng},
faand::{self, faand, fashare, shared_rng, RHO},
fpre::{fpre, Auth, Delta, Key, Mac, Share},
garble::{self, decrypt, encrypt, GarblingKey},
};
Expand All @@ -21,7 +21,7 @@ pub(crate) struct GarbledGate(pub(crate) [Vec<u8>; 4]);
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub(crate) struct Label(pub(crate) u128);

const TRUSTEDDEALER: bool = true;
const TRUSTEDDEALER: bool = false;

impl BitXor for Label {
type Output = Self;
Expand Down Expand Up @@ -312,50 +312,75 @@ pub async fn mpc(
let auth_bits: Vec<Share>;
let mut shares: Vec<Share> = vec![Share(false, Auth(vec![])); num_gates];
let mut labels: Vec<Label> = vec![Label(0); num_gates];
let mut shared_rng = shared_rng(&mut channel, p_own, p_max).await?;
if TRUSTEDDEALER {
channel
.send_to(p_fpre, "random shares", &(secret_bits as u32))
.await?;
random_shares = channel.recv_from(p_fpre, "random shares").await?;
} else {
let mut x: Vec<bool> = (0..secret_bits + 3 * RHO).map(|_| random()).collect();
random_shares = fashare(
&mut channel,
&mut x,
p_own,
p_max,
secret_bits,
delta,
&mut shared_rng,
)
.await?;
}

let mut random_shares = random_shares.into_iter();
for (w, gate) in circuit.wires().iter().enumerate() {
if let Wire::Input(_) | Wire::And(_, _) = gate {
let Some(share) = random_shares.next() else {
return Err(MpcError::MissingShareForWire(w).into());
};
shares[w] = share;
if is_contrib {
labels[w] = Label(random());
}
let mut random_shares = random_shares.into_iter();
for (w, gate) in circuit.wires().iter().enumerate() {
if let Wire::Input(_) | Wire::And(_, _) = gate {
let Some(share) = random_shares.next() else {
return Err(MpcError::MissingShareForWire(w).into());
};
shares[w] = share;
if is_contrib {
labels[w] = Label(random());
}
}
}

// fn-dependent preprocessing:
// fn-dependent preprocessing:

let mut and_shares = Vec::new();
for (w, gate) in circuit.wires().iter().enumerate() {
match gate {
Wire::Input(_) => {}
Wire::Not(x) => {
shares[w] = shares[*x].clone();
labels[w] = labels[*x] ^ delta;
}
Wire::Xor(x, y) => {
shares[w] = &shares[*x] ^ &shares[*y];
labels[w] = labels[*x] ^ labels[*y];
}
Wire::And(x, y) => {
and_shares.push((shares[*x].clone(), shares[*y].clone()));
}
let mut and_shares = Vec::new();
for (w, gate) in circuit.wires().iter().enumerate() {
match gate {
Wire::Input(_) => {}
Wire::Not(x) => {
shares[w] = shares[*x].clone();
labels[w] = labels[*x] ^ delta;
}
Wire::Xor(x, y) => {
shares[w] = &shares[*x] ^ &shares[*y];
labels[w] = labels[*x] ^ labels[*y];
}
Wire::And(x, y) => {
and_shares.push((shares[*x].clone(), shares[*y].clone()));
}
}
}

if TRUSTEDDEALER {
channel.send_to(p_fpre, "AND shares", &and_shares).await?;
auth_bits = channel.recv_from(p_fpre, "AND shares").await?;
} else {
let mut shared_rng = shared_rng(&mut channel, p_own, p_max).await?;
auth_bits = faand(&mut channel, p_own, p_max, num_and_gates, 100, &mut shared_rng, delta).await?.2;
auth_bits = faand(
&mut channel,
and_shares,
p_own,
p_max,
num_and_gates, //TODO figure this out
num_and_gates,
&mut shared_rng,
delta,
)
.await?
.2;
}

let mut auth_bits = auth_bits.into_iter();
Expand Down

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