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use crate::{
encrypt::{encrypt_share, EncryptError, PublicKey},
field::FieldElement,
polynomial::{poly_fft, PolyAuxMemory},
prng::{Prng, PrngError},
util::{proof_length, unpack_proof_mut},
vdaf::suite::Suite,
};
use std::convert::TryFrom;
#[derive(Debug)]
pub struct Client<F: FieldElement> {
prng: Prng<F>,
dimension: usize,
points_f: Vec<F>,
points_g: Vec<F>,
evals_f: Vec<F>,
evals_g: Vec<F>,
poly_mem: PolyAuxMemory<F>,
public_key1: PublicKey,
public_key2: PublicKey,
}
#[derive(Debug, thiserror::Error)]
pub enum ClientError {
#[error("input size exceeds field capacity")]
InputSizeExceedsFieldCapacity,
#[error("input size exceeds field capacity")]
InputSizeExceedsMemoryCapacity,
#[error("encryption/decryption error")]
Encrypt(#[from] EncryptError),
#[error("prng error: {0}")]
Prng(#[from] PrngError),
}
impl<F: FieldElement> Client<F> {
pub fn new(
dimension: usize,
public_key1: PublicKey,
public_key2: PublicKey,
) -> Result<Self, ClientError> {
let n = (dimension + 1).next_power_of_two();
if let Ok(size) = F::Integer::try_from(2 * n) {
if size > F::generator_order() {
return Err(ClientError::InputSizeExceedsFieldCapacity);
}
} else {
return Err(ClientError::InputSizeExceedsMemoryCapacity);
}
Ok(Client {
prng: Prng::generate(Suite::Aes128CtrHmacSha256)?,
dimension,
points_f: vec![F::zero(); n],
points_g: vec![F::zero(); n],
evals_f: vec![F::zero(); 2 * n],
evals_g: vec![F::zero(); 2 * n],
poly_mem: PolyAuxMemory::new(n),
public_key1,
public_key2,
})
}
pub fn encode_simple(&mut self, data: &[F]) -> Result<(Vec<u8>, Vec<u8>), ClientError> {
let copy_data = |share_data: &mut [F]| {
share_data[..].clone_from_slice(data);
};
Ok(self.encode_with(copy_data)?)
}
pub fn encode_with<G>(&mut self, init_function: G) -> Result<(Vec<u8>, Vec<u8>), EncryptError>
where
G: FnOnce(&mut [F]),
{
let mut proof = self.prove_with(init_function);
let share2 = crate::prng::secret_share(&mut proof)?;
let share1 = F::slice_into_byte_vec(&proof);
let encrypted_share1 = encrypt_share(&share1, &self.public_key1)?;
let encrypted_share2 = encrypt_share(&share2, &self.public_key2)?;
Ok((encrypted_share1, encrypted_share2))
}
pub(crate) fn prove_with<G>(&mut self, init_function: G) -> Vec<F>
where
G: FnOnce(&mut [F]),
{
let mut proof = vec![F::zero(); proof_length(self.dimension)];
let mut unpacked = unpack_proof_mut(&mut proof, self.dimension).unwrap();
init_function(&mut unpacked.data);
construct_proof(
unpacked.data,
self.dimension,
&mut unpacked.f0,
&mut unpacked.g0,
&mut unpacked.h0,
&mut unpacked.points_h_packed,
self,
);
proof
}
}
pub fn encode_simple<F: FieldElement>(
data: &[F],
public_key1: PublicKey,
public_key2: PublicKey,
) -> Result<(Vec<u8>, Vec<u8>), ClientError> {
let dimension = data.len();
let mut client_memory = Client::new(dimension, public_key1, public_key2)?;
client_memory.encode_simple(data)
}
fn interpolate_and_evaluate_at_2n<F: FieldElement>(
n: usize,
points_in: &[F],
evals_out: &mut [F],
mem: &mut PolyAuxMemory<F>,
) {
poly_fft(
&mut mem.coeffs,
points_in,
&mem.roots_n_inverted,
n,
true,
&mut mem.fft_memory,
);
poly_fft(
evals_out,
&mem.coeffs,
&mem.roots_2n,
2 * n,
false,
&mut mem.fft_memory,
);
}
fn construct_proof<F: FieldElement>(
data: &[F],
dimension: usize,
f0: &mut F,
g0: &mut F,
h0: &mut F,
points_h_packed: &mut [F],
mem: &mut Client<F>,
) {
let n = (dimension + 1).next_power_of_two();
*f0 = mem.prng.next().unwrap();
*g0 = mem.prng.next().unwrap();
mem.points_f[0] = *f0;
mem.points_g[0] = *g0;
*h0 = *f0 * *g0;
#[allow(clippy::needless_range_loop)]
for i in 0..dimension {
mem.points_f[i + 1] = data[i];
mem.points_g[i + 1] = data[i] - F::one();
}
interpolate_and_evaluate_at_2n(n, &mem.points_f, &mut mem.evals_f, &mut mem.poly_mem);
interpolate_and_evaluate_at_2n(n, &mem.points_g, &mut mem.evals_g, &mut mem.poly_mem);
let mut j: usize = 0;
let mut i: usize = 1;
while i < 2 * n {
points_h_packed[j] = mem.evals_f[i] * mem.evals_g[i];
j += 1;
i += 2;
}
}
#[test]
fn test_encode() {
use crate::field::Field32;
let pub_key1 = PublicKey::from_base64(
"BIl6j+J6dYttxALdjISDv6ZI4/VWVEhUzaS05LgrsfswmbLOgNt9HUC2E0w+9RqZx3XMkdEHBHfNuCSMpOwofVQ=",
)
.unwrap();
let pub_key2 = PublicKey::from_base64(
"BNNOqoU54GPo+1gTPv+hCgA9U2ZCKd76yOMrWa1xTWgeb4LhFLMQIQoRwDVaW64g/WTdcxT4rDULoycUNFB60LE=",
)
.unwrap();
let data_u32 = [0u32, 1, 0, 1, 1, 0, 0, 0, 1];
let data = data_u32
.iter()
.map(|x| Field32::from(*x))
.collect::<Vec<Field32>>();
let encoded_shares = encode_simple(&data, pub_key1, pub_key2);
assert!(encoded_shares.is_ok());
}