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- // We really want points to be capital letters and scalars to be
- // lowercase letters
- #![allow(non_snake_case)]
- pub mod aligned_memory_mt;
- pub mod params;
- pub mod spiral_mt;
- use aes::cipher::{BlockEncrypt, KeyInit};
- use aes::Aes128Enc;
- use aes::Block;
- use std::env;
- use std::mem;
- use std::time::Instant;
- use subtle::Choice;
- use subtle::ConditionallySelectable;
- use rand::RngCore;
- use sha2::Digest;
- use sha2::Sha256;
- use sha2::Sha512;
- use curve25519_dalek::constants as dalek_constants;
- use curve25519_dalek::ristretto::CompressedRistretto;
- use curve25519_dalek::ristretto::RistrettoBasepointTable;
- use curve25519_dalek::ristretto::RistrettoPoint;
- use curve25519_dalek::scalar::Scalar;
- use spiral_rs::client::*;
- use spiral_rs::params::*;
- use spiral_rs::server::*;
- use crate::spiral_mt::*;
- use lazy_static::lazy_static;
- type DbEntry = u64;
- // Generators of the Ristretto group (the standard B and another one C,
- // for which the DL relationship is unknown), and their precomputed
- // multiplication tables. Used for the Oblivious Transfer protocol
- lazy_static! {
- pub static ref OT_B: RistrettoPoint = dalek_constants::RISTRETTO_BASEPOINT_POINT;
- pub static ref OT_C: RistrettoPoint =
- RistrettoPoint::hash_from_bytes::<Sha512>(b"OT Generator C");
- pub static ref OT_B_TABLE: RistrettoBasepointTable = dalek_constants::RISTRETTO_BASEPOINT_TABLE;
- pub static ref OT_C_TABLE: RistrettoBasepointTable = RistrettoBasepointTable::create(&OT_C);
- }
- // XOR a 16-byte slice into a Block (which will be used as an AES key)
- fn xor16(outar: &mut Block, inar: &[u8; 16]) {
- for i in 0..16 {
- outar[i] ^= inar[i];
- }
- }
- // Encrypt a database of 2^r elements, where each element is a DbEntry,
- // using the 2*r provided keys (r pairs of keys). Also add the provided
- // blinding factor to each element before encryption (the same blinding
- // factor for all elements). Each element is encrypted in AES counter
- // mode, with the counter being the element number and the key computed
- // as the XOR of r of the provided keys, one from each pair, according
- // to the bits of the element number. Outputs a byte vector containing
- // the encrypted database.
- fn encdb_xor_keys(db: &[DbEntry], keys: &[[u8; 16]], r: usize, blind: DbEntry) -> Vec<u8> {
- let num_records: usize = 1 << r;
- let mut ret = Vec::<u8>::with_capacity(num_records * mem::size_of::<DbEntry>());
- for j in 0..num_records {
- let mut key = Block::from([0u8; 16]);
- for i in 0..r {
- let bit = if (j & (1 << i)) == 0 { 0 } else { 1 };
- xor16(&mut key, &keys[2 * i + bit]);
- }
- let aes = Aes128Enc::new(&key);
- let mut block = Block::from([0u8; 16]);
- block[0..8].copy_from_slice(&j.to_le_bytes());
- aes.encrypt_block(&mut block);
- let aeskeystream = DbEntry::from_le_bytes(block[0..8].try_into().unwrap());
- let encelem = (db[j].wrapping_add(blind)) ^ aeskeystream;
- ret.extend(encelem.to_le_bytes());
- }
- ret
- }
- // Generate the keys for encrypting the database
- fn gen_db_enc_keys(r: usize) -> Vec<[u8; 16]> {
- let mut keys: Vec<[u8; 16]> = Vec::new();
- let mut rng = rand::thread_rng();
- for _ in 0..2 * r {
- let mut k: [u8; 16] = [0; 16];
- rng.fill_bytes(&mut k);
- keys.push(k);
- }
- keys
- }
- // 1-out-of-2 Oblivious Transfer (OT)
- fn ot12_request(sel: Choice) -> ((Choice, Scalar), [u8; 32]) {
- let Btable: &RistrettoBasepointTable = &OT_B_TABLE;
- let C: &RistrettoPoint = &OT_C;
- let mut rng = rand07::thread_rng();
- let x = Scalar::random(&mut rng);
- let xB = &x * Btable;
- let CmxB = C - xB;
- let P = RistrettoPoint::conditional_select(&xB, &CmxB, sel);
- ((sel, x), P.compress().to_bytes())
- }
- fn ot12_serve(query: &[u8; 32], m0: &[u8; 16], m1: &[u8; 16]) -> [u8; 64] {
- let Btable: &RistrettoBasepointTable = &OT_B_TABLE;
- let Ctable: &RistrettoBasepointTable = &OT_C_TABLE;
- let mut rng = rand07::thread_rng();
- let y = Scalar::random(&mut rng);
- let yB = &y * Btable;
- let yC = &y * Ctable;
- let P = CompressedRistretto::from_slice(query).decompress().unwrap();
- let yP0 = y * P;
- let yP1 = yC - yP0;
- let mut HyP0 = Sha256::digest(yP0.compress().as_bytes());
- for i in 0..16 {
- HyP0[i] ^= m0[i];
- }
- let mut HyP1 = Sha256::digest(yP1.compress().as_bytes());
- for i in 0..16 {
- HyP1[i] ^= m1[i];
- }
- let mut ret = [0u8; 64];
- ret[0..32].copy_from_slice(yB.compress().as_bytes());
- ret[32..48].copy_from_slice(&HyP0[0..16]);
- ret[48..64].copy_from_slice(&HyP1[0..16]);
- ret
- }
- fn ot12_receive(state: (Choice, Scalar), response: &[u8; 64]) -> [u8; 16] {
- let yB = CompressedRistretto::from_slice(&response[0..32])
- .decompress()
- .unwrap();
- let yP = state.1 * yB;
- let mut HyP = Sha256::digest(yP.compress().as_bytes());
- for i in 0..16 {
- HyP[i] ^= u8::conditional_select(&response[32 + i], &response[48 + i], state.0);
- }
- HyP[0..16].try_into().unwrap()
- }
- // Obliviously fetch the key for element q of the database (which has
- // 2^r elements total). Each bit of q is used in a 1-out-of-2 OT to get
- // one of the keys in each of the r pairs of keys on the server side.
- // The resulting r keys are XORed together.
- fn otkey_request(q: usize, r: usize) -> (Vec<(Choice, Scalar)>, Vec<[u8; 32]>) {
- let mut state: Vec<(Choice, Scalar)> = Vec::with_capacity(r);
- let mut query: Vec<[u8; 32]> = Vec::with_capacity(r);
- for i in 0..r {
- let bit = ((q >> i) & 1) as u8;
- let (si, qi) = ot12_request(bit.into());
- state.push(si);
- query.push(qi);
- }
- (state, query)
- }
- fn otkey_serve(query: Vec<[u8; 32]>, keys: &Vec<[u8; 16]>) -> Vec<[u8; 64]> {
- let r = query.len();
- assert!(keys.len() == 2 * r);
- let mut response: Vec<[u8; 64]> = Vec::with_capacity(r);
- for i in 0..r {
- response.push(ot12_serve(&query[i], &keys[2 * i], &keys[2 * i + 1]));
- }
- response
- }
- fn otkey_receive(state: Vec<(Choice, Scalar)>, response: &Vec<[u8; 64]>) -> Block {
- let r = state.len();
- assert!(response.len() == r);
- let mut key = Block::from([0u8; 16]);
- for i in 0..r {
- xor16(&mut key, &ot12_receive(state[i], &response[i]));
- }
- key
- }
- // Having received the key for element q with r parallel 1-out-of-2 OTs,
- // and having received the encrypted element with (non-symmetric) PIR,
- // use the key to decrypt the element.
- fn otkey_decrypt(key: &Block, q: usize, encelement: DbEntry) -> DbEntry {
- let aes = Aes128Enc::new(key);
- let mut block = Block::from([0u8; 16]);
- block[0..8].copy_from_slice(&q.to_le_bytes());
- aes.encrypt_block(&mut block);
- let aeskeystream = DbEntry::from_le_bytes(block[0..8].try_into().unwrap());
- encelement ^ aeskeystream
- }
- // Things that are only done once total, not once for each SPIR
- fn one_time_setup() {
- // Resolve the lazy statics
- let _B: &RistrettoPoint = &OT_B;
- let _Btable: &RistrettoBasepointTable = &OT_B_TABLE;
- let _C: &RistrettoPoint = &OT_C;
- let _Ctable: &RistrettoBasepointTable = &OT_C_TABLE;
- }
- fn print_params_summary(params: &Params) {
- let db_elem_size = params.item_size();
- let total_size = params.num_items() * db_elem_size;
- println!(
- "Using a {} x {} byte database ({} bytes total)",
- params.num_items(),
- db_elem_size,
- total_size
- );
- }
- fn main() {
- let args: Vec<String> = env::args().collect();
- if args.len() != 2 && args.len() != 3 {
- println!("Usage: {} r [num_threads]\nr = log_2(num_records)", args[0]);
- return;
- }
- let r: usize = args[1].parse().unwrap();
- let mut num_threads = 1usize;
- if args.len() == 3 {
- num_threads = args[2].parse().unwrap();
- }
- let num_records = 1 << r;
- println!("===== ONE-TIME SETUP =====\n");
- let otsetup_start = Instant::now();
- let spiral_params = params::get_spiral_params(r);
- let mut rng = rand::thread_rng();
- one_time_setup();
- let otsetup_us = otsetup_start.elapsed().as_micros();
- print_params_summary(&spiral_params);
- println!("OT one-time setup: {} µs", otsetup_us);
- // One-time setup for the Spiral client
- let spc_otsetup_start = Instant::now();
- let mut clientrng = rand::thread_rng();
- let mut client = Client::init(&spiral_params, &mut clientrng);
- let pub_params = client.generate_keys();
- let pub_params_buf = pub_params.serialize();
- let spc_otsetup_us = spc_otsetup_start.elapsed().as_micros();
- let spiral_blocking_factor = spiral_params.db_item_size / mem::size_of::<DbEntry>();
- println!(
- "Spiral client one-time setup: {} µs, {} bytes",
- spc_otsetup_us,
- pub_params_buf.len()
- );
- println!("\n===== PREPROCESSING =====\n");
- // Spiral preprocessing: create a PIR lookup for an element at a
- // random location
- let spc_query_start = Instant::now();
- let rand_idx = (rng.next_u64() as usize) % num_records;
- let rand_pir_idx = rand_idx / spiral_blocking_factor;
- println!("rand_idx = {} rand_pir_idx = {}", rand_idx, rand_pir_idx);
- let spc_query = client.generate_query(rand_pir_idx);
- let spc_query_buf = spc_query.serialize();
- let spc_query_us = spc_query_start.elapsed().as_micros();
- println!(
- "Spiral query: {} µs, {} bytes",
- spc_query_us,
- spc_query_buf.len()
- );
- // Create the database encryption keys and do the OT to fetch the
- // right one, but don't actually encrypt the database yet
- let dbkeys = gen_db_enc_keys(r);
- let otkeyreq_start = Instant::now();
- let (keystate, keyquery) = otkey_request(rand_idx, r);
- let keyquerysize = keyquery.len() * keyquery[0].len();
- let otkeyreq_us = otkeyreq_start.elapsed().as_micros();
- let otkeysrv_start = Instant::now();
- let keyresponse = otkey_serve(keyquery, &dbkeys);
- let keyrespsize = keyresponse.len() * keyresponse[0].len();
- let otkeysrv_us = otkeysrv_start.elapsed().as_micros();
- let otkeyrcv_start = Instant::now();
- let otkey = otkey_receive(keystate, &keyresponse);
- let otkeyrcv_us = otkeyrcv_start.elapsed().as_micros();
- println!("key OT query in {} µs, {} bytes", otkeyreq_us, keyquerysize);
- println!("key OT serve in {} µs, {} bytes", otkeysrv_us, keyrespsize);
- println!("key OT receive in {} µs", otkeyrcv_us);
- // Create a database with recognizable contents
- let mut db: Vec<DbEntry> = ((0 as DbEntry)..(num_records as DbEntry))
- .map(|x| 10000001 * x)
- .collect();
- println!("\n===== RUNTIME =====\n");
- // Pick the record we actually want to query
- let q = (rng.next_u64() as usize) % num_records;
- // Compute the offset from the record index we're actually looking
- // for to the random one we picked earlier. Tell it to the server,
- // who will rotate right the database by that amount before
- // encrypting it.
- let idx_offset = (num_records + rand_idx - q) % num_records;
- println!("Send to server {} bytes", 8 /* sizeof(idx_offset) */);
- // The server rotates, blinds, and encrypts the database
- let blind: DbEntry = 20;
- let encdb_start = Instant::now();
- db.rotate_right(idx_offset);
- let encdb = encdb_xor_keys(&db, &dbkeys, r, blind);
- let encdb_us = encdb_start.elapsed().as_micros();
- println!("Server encrypt database {} µs", encdb_us);
- // Load the encrypted database into Spiral
- let sps_loaddb_start = Instant::now();
- let sps_db = load_db_from_slice_mt(&spiral_params, &encdb, num_threads);
- let sps_loaddb_us = sps_loaddb_start.elapsed().as_micros();
- println!("Server load database {} µs", sps_loaddb_us);
- // Do the PIR query
- let sps_query_start = Instant::now();
- let sps_query = Query::deserialize(&spiral_params, &spc_query_buf);
- let sps_response = process_query(&spiral_params, &pub_params, &sps_query, sps_db.as_slice());
- let sps_query_us = sps_query_start.elapsed().as_micros();
- println!(
- "Server compute response {} µs, {} bytes (*including* the above expansion time)",
- sps_query_us,
- sps_response.len()
- );
- // Decode the response to yield the whole Spiral block
- let spc_recv_start = Instant::now();
- let encdbblock = client.decode_response(sps_response.as_slice());
- // Extract the one encrypted DbEntry we were looking for (and the
- // only one we are able to decrypt)
- let entry_in_block = rand_idx % spiral_blocking_factor;
- let loc_in_block = entry_in_block * mem::size_of::<DbEntry>();
- let loc_in_block_end = (entry_in_block + 1) * mem::size_of::<DbEntry>();
- let encdbentry = DbEntry::from_le_bytes(
- encdbblock[loc_in_block..loc_in_block_end]
- .try_into()
- .unwrap(),
- );
- let decdbentry = otkey_decrypt(&otkey, rand_idx, encdbentry);
- let spc_recv_us = spc_recv_start.elapsed().as_micros();
- println!("Client decode response {} µs", spc_recv_us);
- println!("index = {}, Response = {}", q, decdbentry);
- }
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