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Simplify client implementation - make it easier to read
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Signed-off-by: Anjan Roy <[email protected]>
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@itzmeanjan
itzmeanjan committed Oct 22, 2024
1 parent cf8c0d6 commit 220c2e8
Showing 1 changed file with 31 additions and 28 deletions.
59 changes: 31 additions & 28 deletions include/frodoPIR/client.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -37,10 +37,22 @@ template<size_t λ, size_t db_entry_count, size_t db_entry_byte_len, size_t mat_
struct client_t
{
public:
// Compile-time computable values.
static constexpr auto parsed_db_num_cols = frodoPIR_matrix::get_required_num_columns(db_entry_byte_len, mat_element_bitlen);
static constexpr auto pub_mat_M_byte_len = lwe_dimension * parsed_db_num_cols * sizeof(frodoPIR_matrix::zq_t);
static constexpr auto query_byte_len = db_entry_count * sizeof(frodoPIR_matrix::zq_t);
static constexpr auto response_byte_len = parsed_db_num_cols * sizeof(frodoPIR_matrix::zq_t);

// Type aliases.
using pub_mat_A_t = frodoPIR_matrix::matrix_t<lwe_dimension, db_entry_count>;
using pub_mat_M_t = frodoPIR_matrix::matrix_t<lwe_dimension, parsed_db_num_cols>;
using secret_vec_t = frodoPIR_vector::row_vector_t<lwe_dimension>;
using error_vec_t = frodoPIR_vector::row_vector_t<db_entry_count>;
using query_t = client_query_t<db_entry_count, db_entry_byte_len, mat_element_bitlen>;
using response_t = frodoPIR_vector::row_vector_t<parsed_db_num_cols>;

// Constructor(s)
explicit constexpr client_t(
frodoPIR_matrix::matrix_t<lwe_dimension, db_entry_count> pub_matA,
frodoPIR_matrix::matrix_t<lwe_dimension, frodoPIR_matrix::get_required_num_columns(db_entry_byte_len, mat_element_bitlen)> pub_matM)
explicit constexpr client_t(auto pub_matA, auto pub_matM)
: A(std::move(pub_matA))
, M(std::move(pub_matM))
{
Expand All @@ -53,15 +65,10 @@ struct client_t

// Given a `λ` -bit seed and a byte serialized public matrix M, computed by frodoPIR server, this routine can be used
// for setting up FrodoPIR client, ready to generate queries and process server response.
static forceinline constexpr client_t setup(
std::span<const uint8_t, λ / std::numeric_limits<uint8_t>::digits> seed_μ,
std::span<const uint8_t, lwe_dimension * frodoPIR_matrix::get_required_num_columns(db_entry_byte_len, mat_element_bitlen) * sizeof(frodoPIR_matrix::zq_t)>
pub_matM_bytes)
static forceinline constexpr client_t setup(std::span<const uint8_t, λ / std::numeric_limits<uint8_t>::digits> seed_μ,
std::span<const uint8_t, pub_mat_M_byte_len> pub_matM_bytes)
{
constexpr auto cols = frodoPIR_matrix::get_required_num_columns(db_entry_byte_len, mat_element_bitlen);

return client_t(frodoPIR_matrix::matrix_t<lwe_dimension, db_entry_count>::template generate<λ>(seed_μ),
frodoPIR_matrix::matrix_t<lwe_dimension, cols>::from_le_bytes(pub_matM_bytes));
return client_t(pub_mat_A_t::template generate<λ>(seed_μ), pub_mat_M_t::from_le_bytes(pub_matM_bytes));
}

// Given `n` -many database row indices, this routine prepares `n` -many queries, for enquiring their values,
Expand Down Expand Up @@ -90,13 +97,13 @@ struct client_t
return false;
}

const auto s = frodoPIR_vector::row_vector_t<lwe_dimension>::sample_from_uniform_ternary_distribution(prng); // secret vector
const auto e = frodoPIR_vector::row_vector_t<db_entry_count>::sample_from_uniform_ternary_distribution(prng); // error vector
const auto s = secret_vec_t::sample_from_uniform_ternary_distribution(prng); // secret vector
const auto e = error_vec_t::sample_from_uniform_ternary_distribution(prng); // error vector

const auto b = s * this->A + e;
const auto c = s * this->M;

this->queries[db_row_index] = client_query_t<db_entry_count, db_entry_byte_len, mat_element_bitlen>{
this->queries[db_row_index] = query_t{
.status = query_status_t::prepared,
.db_index = db_row_index,
.b = b,
Expand All @@ -112,8 +119,7 @@ struct client_t
//
// (a) Query is not yet prepared for requested database row index.
// (b) Query is already sent to server for requested database row index.
[[nodiscard("Must use status of query finalization")]] constexpr bool query(const size_t db_row_index,
std::span<uint8_t, db_entry_count * sizeof(frodoPIR_matrix::zq_t)> query_bytes)
[[nodiscard("Must use status of query finalization")]] constexpr bool query(const size_t db_row_index, std::span<uint8_t, query_byte_len> query_bytes)
{
if (!this->queries.contains(db_row_index)) {
return false;
Expand All @@ -139,10 +145,9 @@ struct client_t
//
// (a) Query is not yet prepared for requested database row index.
// (b) Query has not yet been sent to server, so can't process response for it.
[[nodiscard("Must use status of response decoding")]] constexpr bool process_response(
const size_t db_row_index,
std::span<const uint8_t, frodoPIR_matrix::get_required_num_columns(db_entry_byte_len, mat_element_bitlen) * sizeof(frodoPIR_matrix::zq_t)> response_bytes,
std::span<uint8_t, db_entry_byte_len> db_row_bytes)
[[nodiscard("Must use status of response decoding")]] constexpr bool process_response(const size_t db_row_index,
std::span<const uint8_t, response_byte_len> response_bytes,
std::span<uint8_t, db_entry_byte_len> db_row_bytes)
{
if (!this->queries.contains(db_row_index)) {
return false;
Expand All @@ -155,12 +160,10 @@ struct client_t
constexpr auto rounding_factor = static_cast<frodoPIR_matrix::zq_t>(frodoPIR_matrix::Q / rho);
constexpr auto rounding_floor = rounding_factor / 2;

constexpr size_t db_matrix_row_width = frodoPIR_matrix::get_required_num_columns(db_entry_byte_len, mat_element_bitlen);

frodoPIR_vector::row_vector_t<db_matrix_row_width> db_matrix_row{};
auto c_tilda = frodoPIR_vector::row_vector_t<db_matrix_row_width>::from_le_bytes(response_bytes);
response_t db_matrix_row{};
auto c_tilda = response_t::from_le_bytes(response_bytes);

for (size_t idx = 0; idx < db_matrix_row_width; idx++) {
for (size_t idx = 0; idx < parsed_db_num_cols; idx++) {
const auto unscaled_res = c_tilda[idx] - this->queries[db_row_index].c[idx];

const auto scaled_res = unscaled_res / rounding_factor;
Expand All @@ -181,9 +184,9 @@ struct client_t
}

private:
frodoPIR_matrix::matrix_t<lwe_dimension, db_entry_count> A{};
frodoPIR_matrix::matrix_t<lwe_dimension, frodoPIR_matrix::get_required_num_columns(db_entry_byte_len, mat_element_bitlen)> M{};
std::unordered_map<size_t, client_query_t<db_entry_count, db_entry_byte_len, mat_element_bitlen>> queries{};
pub_mat_A_t A{};
pub_mat_M_t M{};
std::unordered_map<size_t, query_t> queries{};
};

}

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