implement min, max, mux

examples/bomberman.rs

@@ -34,6 +34,8 @@ fn coordinates_is_equal(a: &Coordinates, b: &Coordinates) ->
     &(a.x().eq(b.x())) & &(a.y().eq(b.y()))
 }
 
+/// Traverse the map with `p0` moves and check whether any of the moves equal
+/// bomb coordinates (in encrypted domain)
 fn traverse_map(p0: &[Coordinates<FheUint8>], bomb_coords: &[Coordinates<FheUint8>]) -> FheBool {
     // First move
     let mut out = coordinates_is_equal(&p0[0], &bomb_coords[0]);
@@ -52,23 +54,23 @@ fn traverse_map(p0: &[Coordinates], bomb_coords: &[Coordinates
 }
 
 // Do you recall bomberman? It's an interesting game where the bomberman has to
-// cross the map without stepping on strategically placed bombs all across the
+// cross the map without stepping on strategically placed bombs all over the
 // map. Below we implement a very basic prototype of bomberman with 4 players.
 //
-// The map has 256 tiles with bottom left-most tile labelled with coordinate
-// (0,0) and top right-most tile labelled with coordinate (255, 255). There are
+// The map has 256 tiles with bottom left-most tile labelled with coordinates
+// (0,0) and top right-most tile labelled with coordinates (255, 255). There are
 // 4 players: Player 0, Player 1, Player 2, Player 3. Player 0's task is to walk
 // across the map with fixed no. of moves while preventing itself from stepping
-// on any of the bombs placed across the map by Player 1, 2, and 3.
+// on any of the bombs placed on the map by Player 1, 2, and 3.
 //
 // The twist is that Player 0's moves and the locations of bombs placed by other
 // players are encrypted. Player 0 moves across the map in encrypted domain.
 // Only a boolean output indicating whether player 0 survived after all the
 // moves or killed itself by stepping onto a bomb is revealed at the end. If
-// player 0 survives, Player 1, 2, 3 never learn what moves did it make. If
-// player 0 kills itself by stepping onto a bomb, it only learns that bomb was
-// placed on one coordinates it moved to. Moreover, Player 1, 2, 3 never learn
-// about locations of each other bombs or even whose bomb killed Player 1.
+// player 0 survives, Player 1, 2, 3 never learn what moves did Player 0 make.
+// If Player 0 kills itself by stepping onto a bomb, it only learns that bomb
+// was placed on one of the coordinates it moved to. Moreover, Player 1, 2, 3
+// never learn locations of each other bombs or whose bomb killed Player 0.
 fn main() {
     set_parameter_set(ParameterSelector::NonInteractiveLTE4Party);
 
@@ -81,29 +83,34 @@ fn main() {
 
     // Client side //
 
+    // Players generate client keys
     let cks = (0..no_of_parties).map(|_| gen_client_key()).collect_vec();
 
+    // Players generate server keys
     let server_key_shares = cks
         .iter()
         .enumerate()
         .map(|(index, k)| gen_server_key_share(index, no_of_parties, k))
         .collect_vec();
 
-    // encrypt inputs
+    // Player 0 describes its moves as sequence of coordinates on the map
     let no_of_moves = 10;
     let player_0_moves = (0..no_of_moves)
         .map(|_| Coordinates::new(thread_rng().gen::<u8>(), thread_rng().gen()))
         .collect_vec();
+    // Coordinates of bomb placed by Player 1
     let player_1_bomb = Coordinates::new(thread_rng().gen::<u8>(), thread_rng().gen());
+    // Coordinates of bomb placed by Player 2
     let player_2_bomb = Coordinates::new(thread_rng().gen::<u8>(), thread_rng().gen());
+    // Coordinates of bomb placed by Player 3
     let player_3_bomb = Coordinates::new(thread_rng().gen::<u8>(), thread_rng().gen());
 
     println!("P0 moves coordinates: {:?}", &player_0_moves);
-    println!("P1 bomb coordinate  : {:?}", &player_1_bomb);
-    println!("P2 bomb coordinate  : {:?}", &player_2_bomb);
-    println!("P3 bomb coordinate  : {:?}", &player_3_bomb);
+    println!("P1 bomb coordinates : {:?}", &player_1_bomb);
+    println!("P2 bomb coordinates : {:?}", &player_2_bomb);
+    println!("P3 bomb coordinates : {:?}", &player_3_bomb);
 
-    // Al players encrypt their private inputs
+    // Players encrypt their private inputs
     let player_0_enc = cks[0].encrypt(
         player_0_moves
             .iter()
@@ -115,14 +122,14 @@ fn main() {
     let player_2_enc = cks[2].encrypt(vec![*player_2_bomb.x(), *player_2_bomb.y()].as_slice());
     let player_3_enc = cks[3].encrypt(vec![*player_3_bomb.x(), *player_3_bomb.y()].as_slice());
 
-    // All player upload the encrypted inputs and server key shates to the server
+    // Players upload the encrypted inputs and server key shares to the server
 
     // Server side //
 
     let server_key = aggregate_server_key_shares(&server_key_shares);
     server_key.set_server_key();
 
-    // server parses all player inputs
+    // server parses Player inputs
     let player_0_moves_enc = {
         let c = player_0_enc
             .unseed::<Vec<Vec<u64>>>()
@@ -147,17 +154,20 @@ fn main() {
         Coordinates::new(c.extract_at(0), c.extract_at(1))
     };
 
-    // run the game
+    // Server runs the game
     let player_0_dead_ct = traverse_map(
         &player_0_moves_enc,
         &vec![player_1_bomb_enc, player_2_bomb_enc, player_3_bomb_enc],
     );
 
-    // All players generate decryption shares
+    // Client side //
+
+    // Players generate decryption shares and send them to each other
     let decryption_shares = cks
         .iter()
         .map(|k| k.gen_decryption_share(&player_0_dead_ct))
         .collect_vec();
+    // Players decrypt to find whether Player 0 survived
     let player_0_dead = cks[0].aggregate_decryption_shares(&player_0_dead_ct, &decryption_shares);
 
     if player_0_dead {

examples/meeting_friends.rs

@@ -1,6 +1,6 @@
 use bin_rs::*;
 use itertools::Itertools;
-use rand::{thread_rng, RngCore};
+use rand::{thread_rng, Rng, RngCore};
 
 struct Location<T>(T, T);
 
@@ -47,17 +47,19 @@ fn should_meet_fhe(
 // Here we write a simple application with two users `a` and `b`. User `a` wants
 // to find (long distance) friends that live in their neighbourhood. User `b` is
 // open to meeting new friends within some distance of their location. Both user
-// `a` and `b` encrypt their location and upload to the server. User `b` also
-// encrypts the distance square threshold within which they are interested in
-// meeting new friends. The server calculates the square of the distance between
-// user a's location and user b's location and returns encrypted boolean output
-// indicating whether square of distance is <= user b's supplied distance square
-// threshold. User `a` then comes online, downloads output ciphertext, produces
-// their decryption share for user `b`, and uploads the decryption share to the
+// `a` and `b` encrypt their locations and upload their encrypted locations to
+// the server. User `b` also encrypts the distance square threshold within which
+// they are interested in meeting new friends. and send encrypted distance
+// square threshold to the server.
+// The server calculates the square of the distance between user a's location
+// and user b's location and produces encrypted boolean output indicating
+// whether square of distance is <= user b's supplied distance square threshold.
+// User `a` then comes online, downloads output ciphertext, produces their
+// decryption share for user `b`, and uploads the decryption share to the
 // server. User `b` comes online, downloads output ciphertext and user a's
 // decryption share, produces their own decryption share, and then decrypts the
-// encrypted boolean output. If the output is `True`, it indicates
-// user `a` is within the distance square threshold defined by user `b`.
+// encrypted boolean output. If the output is `True`, it indicates user `a` is
+// within the distance square threshold defined by user `b`.
 fn main() {
     set_parameter_set(ParameterSelector::NonInteractiveLTE2Party);
 
@@ -73,7 +75,7 @@ fn main() {
     // Generate client keys
     let cks = (0..no_of_parties).map(|_| gen_client_key()).collect_vec();
 
-    // We assign id 0 to client 0 and id 1 to client 1
+    // We assign user_id 0 to client 0 and user_id 1 to client 1
     let a_id = 0;
     let b_id = 1;
     let user_a_secret = &cks[0];
@@ -85,30 +87,30 @@ fn main() {
 
     // User a and b encrypt their locations
     let user_a_secret = &cks[0];
-    let user_a_location = Location::new(50, 60);
+    let user_a_location = Location::new(thread_rng().gen::<u8>(), thread_rng().gen::<u8>());
     let user_a_enc =
         user_a_secret.encrypt(vec![*user_a_location.x(), *user_a_location.y()].as_slice());
 
-    let user_b_location = Location::new(50, 60);
-    // User b also encrypts the distance sq threshold
-    let user_b_threshold = 20;
+    let user_b_location = Location::new(thread_rng().gen::<u8>(), thread_rng().gen::<u8>());
+    // User b also encrypts the distance square threshold
+    let user_b_threshold = 40;
     let user_b_enc = user_b_secret
         .encrypt(vec![*user_b_location.x(), *user_b_location.y(), user_b_threshold].as_slice());
 
     // Server Side //
 
     // Both user a and b upload their private inputs and server key shares to
-    // the server in one shot message
+    // the server in single shot message
     let server_key = aggregate_server_key_shares(&vec![a_server_key_share, b_server_key_share]);
     server_key.set_server_key();
 
     // Server parses private inputs from user a and b
     let user_a_location_enc = {
-        let c = user_a_enc.unseed::<Vec<Vec<u64>>>().key_switch(0);
+        let c = user_a_enc.unseed::<Vec<Vec<u64>>>().key_switch(a_id);
         Location::new(c.extract_at(0), c.extract_at(1))
     };
     let (user_b_location_enc, user_b_threshold_enc) = {
-        let c = user_b_enc.unseed::<Vec<Vec<u64>>>().key_switch(1);
+        let c = user_b_enc.unseed::<Vec<Vec<u64>>>().key_switch(b_id);
         (
             Location::new(c.extract_at(0), c.extract_at(1)),
             c.extract_at(2),
@@ -124,13 +126,13 @@ fn main() {
 
     // Client Side //
 
-    // user a comes online, downloads out_c, produces a decryption share, and
+    // user `a` comes online, downloads `out_c`, produces a decryption share, and
     // uploads the decryption share to the server.
     let a_dec_share = user_a_secret.gen_decryption_share(&out_c);
 
-    // user b comes online downloads user a's decryption share, generates their
+    // user `b` comes online downloads user `a`'s decryption share, generates their
     // own decryption share, decrypts the output ciphertext. If the output is
-    // True, they contact user a to meet.
+    // True, they contact user `a` to meet.
     let b_dec_share = user_b_secret.gen_decryption_share(&out_c);
     let out_bool =
         user_b_secret.aggregate_decryption_shares(&out_c, &vec![b_dec_share, a_dec_share]);

examples/non_interactive_fheuint8.rs

@@ -46,7 +46,7 @@ fn main() {
     let c2_a = thread_rng().gen::<u8>();
     let c2_enc = cks[2].encrypt(vec![c2_a].as_slice());
 
-    // client 1 encrypts its private inputs
+    // client 3 encrypts its private inputs
     let c3_a = thread_rng().gen::<u8>();
     let c3_enc = cks[3].encrypt(vec![c3_a].as_slice());
 
@@ -66,26 +66,26 @@ fn main() {
     // Server side //
 
     // Server receives server key shares from each client and proceeds to aggregate
-    // them to produce server key. After this point, server can use server key share
-    // to evaluate any arbitrary function on encrypted private inputs from the fixed
-    // set of clients
+    // them to produce the server key. After this point, server can use the server
+    // key to evaluate any arbitrary function on encrypted private inputs from
+    // the fixed set of clients
 
-    // aggregate shares and generates server key
+    // aggregate server shares and generate the server key
     let server_key = aggregate_server_key_shares(&server_key_shares);
     server_key.set_server_key();
 
     // Server proceeds to extract private inputs sent by clients
     //
     // To extract client 0's (with user_id=0) private inputs we first key switch
-    // client 0's private inputs from thei secret to ideal secret of the mpc
+    // client 0's private inputs from theit secret to ideal secret of the mpc
     // protocol. To indicate we're key switching client 0's private input we
-    // supply client 0's user_id i.e. we call `key_switch(0)`. Then we extract
+    // supply client 0's `user_id` i.e. we call `key_switch(0)`. Then we extract
     // the first ciphertext by calling `extract_at(0)`.
     //
-    // Since client 0 only encrypted 1 input in batched ciphertext calling
+    // Since client 0 only encrypts 1 input in batched ciphertext, calling
     // extract_at(index) for `index` > 0 will panic. If client 0 had more private
-    // inputs then we can either extract them all at once by `extract_all` or first
-    // `many` of them by `extract_many(many)`
+    // inputs then we can either extract them all at once with `extract_all` or
+    // first `many` of them with `extract_many(many)`
     let ct_c0_a = c0_enc.unseed::<Vec<Vec<u64>>>().key_switch(0).extract_at(0);
 
     let ct_c1_a = c1_enc.unseed::<Vec<Vec<u64>>>().key_switch(1).extract_at(0);
@@ -93,7 +93,7 @@ fn main() {
     let ct_c3_a = c3_enc.unseed::<Vec<Vec<u64>>>().key_switch(3).extract_at(0);
 
     // After extracting each client's private inputs, server proceeds to evaluate
-    // the function1
+    // function1
     let now = std::time::Instant::now();
     let ct_out_f1 = function1_fhe(&ct_c0_a, &ct_c1_a, &ct_c2_a, &ct_c3_a);
     println!("Function1 FHE evaluation time: {:?}", now.elapsed());
@@ -104,10 +104,10 @@ fn main() {
     // Client side //
 
     // In multi-party decryption, each client needs to come online, download output
-    // ciphertext from the server, produce decryption share, and send to other
-    // parties (either via p2p or via server). After receving decryption shares
-    // for output ciphertext from other parties, client can independently decrypt
-    // output ciphertext.
+    // ciphertext from the server, produce "output ciphertext" dependent decryption
+    // share, and send it to other parties (either via p2p or via server). After
+    // receving decryption shares from other parties, clients can independently
+    // decrypt output ciphertext.
 
     // each client produces decryption share
     let decryption_shares = cks
@@ -115,19 +115,19 @@ fn main() {
         .map(|k| k.gen_decryption_share(&ct_out_f1))
         .collect_vec();
 
-    // With all decrytpion shares, client can aggregate the shares and decrypt the
+    // With all decrytpion shares, clients can aggregate the shares and decrypt the
     // ciphertext
     let out_f1 = cks[0].aggregate_decryption_shares(&ct_out_f1, &decryption_shares);
 
-    // we check that output is correct
+    // we check correctness of function1
     let want_out_f1 = function1(c0_a, c1_a, c2_a, c3_a);
     assert_eq!(out_f1, want_out_f1);
 
     // -----------
 
-    // Server key can be re-used for different function with different private
-    // client inputs for same set of clients. Here we run `function2_fhe` for
-    // the same set of client but with new inputs. Client only have to upload their
+    // Server key can be re-used for different functions with different private
+    // client inputs for the same set of clients. Here we run `function2_fhe` for
+    // the same set of client but with new inputs. Clients only have to upload their
     // private inputs to the server this time.
 
     // Each client encrypts their private input
@@ -140,7 +140,7 @@ fn main() {
     let c3_a = thread_rng().gen::<u8>();
     let c3_enc = cks[3].encrypt(vec![c3_a].as_slice());
 
-    // Client upload their private inputs to the server
+    // Clients upload their private inputs to the server
 
     // Server side //
 
@@ -163,7 +163,7 @@ fn main() {
         .map(|k| k.gen_decryption_share(&ct_out_f2))
         .collect_vec();
 
-    // Client independently aggregate the shares and decrypt
+    // Clients independently aggregate the shares and decrypt
     let out_f2 = cks[0].aggregate_decryption_shares(&ct_out_f2, &decryption_shares);
 
     // We check correctness of function2

src/bool/mp_api.rs

@@ -517,7 +517,7 @@ mod tests {
             let ct = seeded_ct.unseed::<Vec<Vec<u64>>>();
 
             let m_back = (0..batch_size)
-                .map(|i| ck.decrypt(&ct.extract(i)))
+                .map(|i| ck.decrypt(&ct.extract_at(i)))
                 .collect_vec();
 
             assert_eq!(m, m_back);
@@ -528,7 +528,7 @@ mod tests {
         fn all_uint8_apis() {
             use num_traits::Euclid;
 
-            use crate::div_zero_error_flag;
+            use crate::{div_zero_error_flag, FheBool};
 
             set_single_party_parameter_sets(SP_TEST_BOOL_PARAMS);
 
@@ -624,7 +624,7 @@ mod tests {
                         }
                     }
 
-                    // Comparisons
+                    // // Comparisons
                     {
                         {
                             let c_eq = c0.eq(&c1);
@@ -681,6 +681,15 @@ mod tests {
                             );
                         }
                     }
+
+                    // mux
+                    {
+                        let selector = thread_rng().gen_bool(0.5);
+                        let selector_enc: FheBool = ck.encrypt(&selector);
+                        let mux_out = ck.decrypt(&c0.mux(&c1, &selector_enc));
+                        let want_mux_out = if selector { m0 } else { m1 };
+                        assert_eq!(mux_out, want_mux_out);
+                    }
                 }
             }
         }

src/lib.rs

@@ -16,13 +16,10 @@ mod utils;
 pub use backend::{
     ArithmeticLazyOps, ArithmeticOps, ModInit, ModularOpsU64, ShoupMatrixFMA, VectorOps,
 };
-// pub use bool::{
-//     aggregate_public_key_shares, aggregate_server_key_shares, gen_client_key,
-// gen_mp_keys_phase1,     gen_mp_keys_phase2, set_mp_seed, set_parameter_set,
-// ParameterSelector, };
+
 pub use bool::*;
 pub use ntt::{Ntt, NttBackendU64, NttInit};
-pub use shortint::{div_zero_error_flag, FheUint8};
+pub use shortint::{div_zero_error_flag, reset_error_flags, FheUint8};
 
 pub use decomposer::{Decomposer, DecomposerIter, DefaultDecomposer};
 
@@ -96,11 +93,6 @@ pub trait RowEntity: Row {
     fn zeros(col: usize) -> Self;
 }
 
-trait Secret {
-    type Element;
-    fn values(&self) -> &[Self::Element];
-}
-
 impl<T> Matrix for Vec<Vec<T>> {
     type MatElement = T;
     type R = Vec<T>;

src/lwe.rs

@@ -173,7 +173,7 @@ mod tests {
         decomposer::DefaultDecomposer,
         random::{DefaultSecureRng, NewWithSeed},
         utils::{fill_random_ternary_secret_with_hamming_weight, WithLocal},
-        MatrixEntity, MatrixMut, Secret,
+        MatrixEntity, MatrixMut,
     };
 
     use super::*;
@@ -185,13 +185,6 @@ mod tests {
         pub(crate) values: Vec<i32>,
     }
 
-    impl Secret for LweSecret {
-        type Element = i32;
-        fn values(&self) -> &[Self::Element] {
-            &self.values
-        }
-    }
-
     impl LweSecret {
         fn random(hw: usize, n: usize) -> LweSecret {
             DefaultSecureRng::with_local_mut(|rng| {
@@ -201,6 +194,10 @@ mod tests {
                 LweSecret { values: out }
             })
         }
+
+        fn values(&self) -> &[i32] {
+            &self.values
+        }
     }
 
     struct LweKeySwitchingKey<M, R> {

src/rgsw/mod.rs

@@ -24,7 +24,7 @@ pub(crate) mod tests {
             fill_random_ternary_secret_with_hamming_weight, generate_prime, negacyclic_mul,
             tests::Stats, ToShoup, TryConvertFrom1, WithLocal,
         },
-        Matrix, MatrixEntity, MatrixMut, Row, RowEntity, RowMut, Secret,
+        Matrix, MatrixEntity, MatrixMut, Row, RowEntity, RowMut,
     };
 
     use super::{
@@ -406,13 +406,6 @@ pub(crate) mod tests {
         pub(crate) values: Vec<i32>,
     }
 
-    impl Secret for RlweSecret {
-        type Element = i32;
-        fn values(&self) -> &[Self::Element] {
-            &self.values
-        }
-    }
-
     impl RlweSecret {
         pub fn random(hw: usize, n: usize) -> RlweSecret {
             DefaultSecureRng::with_local_mut(|rng| {
@@ -422,6 +415,10 @@ pub(crate) mod tests {
                 RlweSecret { values: out }
             })
         }
+
+        fn values(&self) -> &[i32] {
+            &self.values
+        }
     }
 
     fn random_seed() -> [u8; 32] {

src/shortint/mod.rs

@@ -17,6 +17,16 @@ pub fn div_zero_error_flag() -> Option {
     DIV_ZERO_ERROR.with_borrow(|c| c.clone())
 }
 
+/// Reset all error flags
+///
+/// Error flags are thread local. When running multiple circuits in sequence
+/// within a single program you must prevent error flags set during the
+/// execution of previous circuit to affect error flags set during execution of
+/// the next circuit by resetting the flags before starting with next circuit.
+pub fn reset_error_flags() {
+    DIV_ZERO_ERROR.with_borrow_mut(|c| *c = None);
+}
+
 mod frontend {
     use super::ops::{
         arbitrary_bit_adder, arbitrary_bit_division_for_quotient_and_rem, arbitrary_bit_subtractor,
@@ -176,7 +186,9 @@ mod frontend {
     }
 
     mod booleans {
-        use crate::shortint::ops::{arbitrary_bit_comparator, arbitrary_bit_equality};
+        use crate::shortint::ops::{
+            arbitrary_bit_comparator, arbitrary_bit_equality, arbitrary_bit_mux,
+        };
 
         use super::*;
 
@@ -238,6 +250,27 @@ mod frontend {
                     FheBool { data: a_less_b }
                 })
             }
+
+            /// Returns `Self` if `selector = True` else returns `other`
+            pub fn mux(&self, other: &FheUint8, selector: &FheBool) -> FheUint8 {
+                BoolEvaluator::with_local_mut(|e| {
+                    let key = RuntimeServerKey::global();
+                    let out = arbitrary_bit_mux(e, selector.data(), self.data(), other.data(), key);
+                    FheUint8 { data: out }
+                })
+            }
+
+            /// max(`Self`, `other`)
+            pub fn max(&self, other: &FheUint8) -> FheUint8 {
+                let self_gt = self.gt(other);
+                self.mux(other, &self_gt)
+            }
+
+            /// min(`Self`, `other`)
+            pub fn min(&self, other: &FheUint8) -> FheUint8 {
+                let self_lt = self.lt(other);
+                self.mux(other, &self_lt)
+            }
         }
     }
 }

src/shortint/ops.rs

@@ -114,9 +114,10 @@ pub(super) fn bit_mux(
     // (s&a) | ((1-s)^b)
     let not_selector = evaluator.not(&selector);
 
-    let s_and_a = evaluator.and(&selector, if_true, key);
+    let mut s_and_a = evaluator.and(&selector, if_true, key);
     let s_and_b = evaluator.and(&not_selector, if_false, key);
-    evaluator.or(&s_and_a, &s_and_b, key)
+    evaluator.or(&mut s_and_a, &s_and_b, key);
+    s_and_a
 }
 
 pub(super) fn arbitrary_bit_mux<E: BooleanGates>(
@@ -131,9 +132,10 @@ pub(super) fn arbitrary_bit_mux(
 
     izip!(if_true.iter(), if_false.iter())
         .map(|(a, b)| {
-            let s_and_a = evaluator.and(&selector, a, key);
+            let mut s_and_a = evaluator.and(&selector, a, key);
             let s_and_b = evaluator.and(&not_selector, b, key);
-            evaluator.or(&s_and_a, &s_and_b, key)
+            evaluator.or_inplace(&mut s_and_a, &s_and_b, key);
+            s_and_a
         })
         .collect()
 }