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use crate::{
encrypt::{decrypt_share, EncryptError, PrivateKey},
field::{merge_vector, FieldElement, FieldError},
polynomial::{poly_interpret_eval, PolyAuxMemory},
prng::{extract_share_from_seed, Prng, PrngError},
util::{proof_length, unpack_proof, SerializeError},
vdaf::suite::Suite,
};
use serde::{Deserialize, Serialize};
#[derive(Debug, thiserror::Error)]
pub enum ServerError {
#[error("encryption/decryption error")]
Encrypt(#[from] EncryptError),
#[error("finite field operation error")]
Field(#[from] FieldError),
#[error("serialization/deserialization error")]
Serialize(#[from] SerializeError),
#[error("getrandom: {0}")]
GetRandom(#[from] getrandom::Error),
#[error("prng error: {0}")]
Prng(#[from] PrngError),
}
#[derive(Debug)]
pub struct ValidationMemory<F> {
points_f: Vec<F>,
points_g: Vec<F>,
points_h: Vec<F>,
poly_mem: PolyAuxMemory<F>,
}
impl<F: FieldElement> ValidationMemory<F> {
pub fn new(dimension: usize) -> Self {
let n: usize = (dimension + 1).next_power_of_two();
ValidationMemory {
points_f: vec![F::zero(); n],
points_g: vec![F::zero(); n],
points_h: vec![F::zero(); 2 * n],
poly_mem: PolyAuxMemory::new(n),
}
}
}
#[derive(Debug)]
pub struct Server<F> {
prng: Prng<F>,
dimension: usize,
is_first_server: bool,
accumulator: Vec<F>,
validation_mem: ValidationMemory<F>,
private_key: PrivateKey,
}
impl<F: FieldElement> Server<F> {
pub fn new(
dimension: usize,
is_first_server: bool,
private_key: PrivateKey,
) -> Result<Server<F>, ServerError> {
Ok(Server {
prng: Prng::generate(Suite::Aes128CtrHmacSha256)?,
dimension,
is_first_server,
accumulator: vec![F::zero(); dimension],
validation_mem: ValidationMemory::new(dimension),
private_key,
})
}
fn deserialize_share(&self, encrypted_share: &[u8]) -> Result<Vec<F>, ServerError> {
let share = decrypt_share(encrypted_share, &self.private_key)?;
Ok(if self.is_first_server {
F::byte_slice_into_vec(&share)?
} else {
let len = proof_length(self.dimension);
extract_share_from_seed(len, &share)?
})
}
pub fn generate_verification_message(
&mut self,
eval_at: F,
share: &[u8],
) -> Result<VerificationMessage<F>, ServerError> {
let share_field = self.deserialize_share(share)?;
generate_verification_message(
self.dimension,
eval_at,
&share_field,
self.is_first_server,
&mut self.validation_mem,
)
}
pub fn aggregate(
&mut self,
share: &[u8],
v1: &VerificationMessage<F>,
v2: &VerificationMessage<F>,
) -> Result<bool, ServerError> {
let share_field = self.deserialize_share(share)?;
let is_valid = is_valid_share(v1, v2);
if is_valid {
merge_vector(&mut self.accumulator, &share_field[..self.dimension])?;
}
Ok(is_valid)
}
pub fn total_shares(&self) -> &[F] {
&self.accumulator
}
pub fn merge_total_shares(&mut self, other_total_shares: &[F]) -> Result<(), ServerError> {
Ok(merge_vector(&mut self.accumulator, other_total_shares)?)
}
pub fn choose_eval_at(&mut self) -> F {
loop {
let eval_at = self.prng.next().unwrap();
if !self.validation_mem.poly_mem.roots_2n.contains(&eval_at) {
break eval_at;
}
}
}
}
#[derive(Debug, Serialize, Deserialize)]
pub struct VerificationMessage<F> {
pub f_r: F,
pub g_r: F,
pub h_r: F,
}
pub fn generate_verification_message<F: FieldElement>(
dimension: usize,
eval_at: F,
proof: &[F],
is_first_server: bool,
mem: &mut ValidationMemory<F>,
) -> Result<VerificationMessage<F>, ServerError> {
let unpacked = unpack_proof(proof, dimension)?;
let proof_length = 2 * (dimension + 1).next_power_of_two();
mem.points_f[0] = *unpacked.f0;
mem.points_g[0] = *unpacked.g0;
mem.points_h[0] = *unpacked.h0;
for (i, x) in unpacked.data.iter().enumerate() {
mem.points_f[i + 1] = *x;
if is_first_server {
mem.points_g[i + 1] = *x - F::one();
} else {
mem.points_g[i + 1] = *x;
}
}
let mut i = 1;
let mut j = 0;
while i < proof_length {
mem.points_h[i] = unpacked.points_h_packed[j];
j += 1;
i += 2;
}
let f_r = poly_interpret_eval(
&mem.points_f,
&mem.poly_mem.roots_n_inverted,
eval_at,
&mut mem.poly_mem.coeffs,
&mut mem.poly_mem.fft_memory,
);
let g_r = poly_interpret_eval(
&mem.points_g,
&mem.poly_mem.roots_n_inverted,
eval_at,
&mut mem.poly_mem.coeffs,
&mut mem.poly_mem.fft_memory,
);
let h_r = poly_interpret_eval(
&mem.points_h,
&mem.poly_mem.roots_2n_inverted,
eval_at,
&mut mem.poly_mem.coeffs,
&mut mem.poly_mem.fft_memory,
);
Ok(VerificationMessage { f_r, g_r, h_r })
}
pub fn is_valid_share<F: FieldElement>(
v1: &VerificationMessage<F>,
v2: &VerificationMessage<F>,
) -> bool {
let f_r = v1.f_r + v2.f_r;
let g_r = v1.g_r + v2.g_r;
let h_r = v1.h_r + v2.h_r;
f_r * g_r == h_r
}
#[cfg(test)]
mod tests {
use super::*;
use crate::{
encrypt::{encrypt_share, PublicKey},
field::{Field32, FieldPriov2},
test_vector::Priov2TestVector,
util::{self, unpack_proof_mut},
};
use serde_json;
#[test]
fn test_validation() {
let dim = 8;
let proof_u32: Vec<u32> = vec![
1, 0, 0, 0, 0, 0, 0, 0, 2052337230, 3217065186, 1886032198, 2533724497, 397524722,
3820138372, 1535223968, 4291254640, 3565670552, 2447741959, 163741941, 335831680,
2567182742, 3542857140, 124017604, 4201373647, 431621210, 1618555683, 267689149,
];
let mut proof: Vec<Field32> = proof_u32.iter().map(|x| Field32::from(*x)).collect();
let share2 = util::tests::secret_share(&mut proof);
let eval_at = Field32::from(12313);
let mut validation_mem = ValidationMemory::new(dim);
let v1 =
generate_verification_message(dim, eval_at, &proof, true, &mut validation_mem).unwrap();
let v2 = generate_verification_message(dim, eval_at, &share2, false, &mut validation_mem)
.unwrap();
assert!(is_valid_share(&v1, &v2));
}
#[test]
fn test_verification_message_serde() {
let dim = 8;
let proof_u32: Vec<u32> = vec![
1, 0, 0, 0, 0, 0, 0, 0, 2052337230, 3217065186, 1886032198, 2533724497, 397524722,
3820138372, 1535223968, 4291254640, 3565670552, 2447741959, 163741941, 335831680,
2567182742, 3542857140, 124017604, 4201373647, 431621210, 1618555683, 267689149,
];
let mut proof: Vec<Field32> = proof_u32.iter().map(|x| Field32::from(*x)).collect();
let share2 = util::tests::secret_share(&mut proof);
let eval_at = Field32::from(12313);
let mut validation_mem = ValidationMemory::new(dim);
let v1 =
generate_verification_message(dim, eval_at, &proof, true, &mut validation_mem).unwrap();
let v2 = generate_verification_message(dim, eval_at, &share2, false, &mut validation_mem)
.unwrap();
let serialized = serde_json::to_string(&v1).unwrap();
let deserialized: VerificationMessage<Field32> = serde_json::from_str(&serialized).unwrap();
assert!(is_valid_share(&deserialized, &v2));
}
#[derive(Debug, Clone, Copy, PartialEq)]
enum Tweak {
None,
WrongInput,
DataPartOfShare,
ZeroTermF,
ZeroTermG,
ZeroTermH,
PointsH,
VerificationF,
VerificationG,
VerificationH,
}
fn tweaks(tweak: Tweak) {
let dim = 123;
let test_vector = Priov2TestVector::new(dim, 0).unwrap();
let mut server1 = test_vector.server_1().unwrap();
let mut server2 = test_vector.server_2().unwrap();
let mut client = test_vector.client().unwrap();
let mut data = vec![FieldPriov2::zero(); dim];
if let Tweak::WrongInput = tweak {
data[0] = FieldPriov2::from(2);
}
let (share1_original, share2) = client.encode_simple(&data).unwrap();
let decrypted_share1 = decrypt_share(&share1_original, &server1.private_key).unwrap();
let mut share1_field = FieldPriov2::byte_slice_into_vec(&decrypted_share1).unwrap();
let unpacked_share1 = unpack_proof_mut(&mut share1_field, dim).unwrap();
let one = FieldPriov2::from(1);
match tweak {
Tweak::DataPartOfShare => unpacked_share1.data[0] += one,
Tweak::ZeroTermF => *unpacked_share1.f0 += one,
Tweak::ZeroTermG => *unpacked_share1.g0 += one,
Tweak::ZeroTermH => *unpacked_share1.h0 += one,
Tweak::PointsH => unpacked_share1.points_h_packed[0] += one,
_ => (),
};
let share1_modified = encrypt_share(
&FieldPriov2::slice_into_byte_vec(&share1_field),
&PublicKey::from(&server1.private_key),
)
.unwrap();
let eval_at = server1.choose_eval_at();
let mut v1 = server1
.generate_verification_message(eval_at, &share1_modified)
.unwrap();
let v2 = server2
.generate_verification_message(eval_at, &share2)
.unwrap();
match tweak {
Tweak::VerificationF => v1.f_r += one,
Tweak::VerificationG => v1.g_r += one,
Tweak::VerificationH => v1.h_r += one,
_ => (),
}
let should_be_valid = matches!(tweak, Tweak::None);
assert_eq!(
server1.aggregate(&share1_modified, &v1, &v2).unwrap(),
should_be_valid
);
assert_eq!(
server2.aggregate(&share2, &v1, &v2).unwrap(),
should_be_valid
);
}
#[test]
fn tweak_none() {
tweaks(Tweak::None);
}
#[test]
fn tweak_input() {
tweaks(Tweak::WrongInput);
}
#[test]
fn tweak_data() {
tweaks(Tweak::DataPartOfShare);
}
#[test]
fn tweak_f_zero() {
tweaks(Tweak::ZeroTermF);
}
#[test]
fn tweak_g_zero() {
tweaks(Tweak::ZeroTermG);
}
#[test]
fn tweak_h_zero() {
tweaks(Tweak::ZeroTermH);
}
#[test]
fn tweak_h_points() {
tweaks(Tweak::PointsH);
}
#[test]
fn tweak_f_verif() {
tweaks(Tweak::VerificationF);
}
#[test]
fn tweak_g_verif() {
tweaks(Tweak::VerificationG);
}
#[test]
fn tweak_h_verif() {
tweaks(Tweak::VerificationH);
}
}