mp-spdz-rs: ffi: Add bindings for ciphertext <> plaintext ops

mp-spdz-rs/build.rs

@@ -63,7 +63,7 @@ fn main() {
     }
 
     // Build cache flags
-    println!("cargo:rerun-if-changed=../MP-SPDZ");
+    println!("cargo:rerun-if-changed=src/include/MP-SPDZ");
 }
 
 /// Get the vendor of the current host

mp-spdz-rs/src/ffi.rs

@@ -40,6 +40,8 @@ mod ffi_inner {
 
         // `Ciphertext`
         type Ciphertext;
+        fn add_plaintext(c0: &Ciphertext, p1: &Plaintext_mod_prime) -> UniquePtr<Ciphertext>;
+        fn mul_plaintext(c0: &Ciphertext, p1: &Plaintext_mod_prime) -> UniquePtr<Ciphertext>;
         fn add_ciphertexts(c0: &Ciphertext, c1: &Ciphertext) -> UniquePtr<Ciphertext>;
         fn mul_ciphertexts(c0: &Ciphertext, c1: &Ciphertext, pk: &FHE_PK) -> UniquePtr<Ciphertext>;
     }
@@ -65,18 +67,71 @@ mod test {
         (params, keypair)
     }
 
+    /// Create a plaintext value with the given integer in the first slot
+    fn plaintext_int(val: u32, params: &FHE_Params) -> UniquePtr<Plaintext_mod_prime> {
+        let mut plaintext = new_plaintext(params);
+        set_element_int(plaintext.pin_mut(), 0 /* idx */, val);
+
+        plaintext
+    }
+
     /// Create a ciphertext encrypting a single integer in the zero'th slot
     fn encrypt_int(
-        params: &FHE_Params,
-        keypair: &FHE_KeyPair,
         value: u32,
+        keypair: &FHE_KeyPair,
+        params: &FHE_Params,
     ) -> UniquePtr<Ciphertext> {
-        let mut plaintext = new_plaintext(params);
-        set_element_int(plaintext.pin_mut(), 0 /* idx */, value);
-
+        let mut plaintext = plaintext_int(value, params);
         encrypt(keypair, &plaintext)
     }
 
+    /// Tests addition of a plaintext to a ciphertext
+    #[test]
+    fn test_plaintext_addition() {
+        let mut rng = thread_rng();
+        let (params, mut keypair) = setup_fhe(0, 254);
+
+        // Add a plaintext to a ciphertext
+        let val1 = rng.next_u32() / 2;
+        let val2 = rng.next_u32() / 2;
+
+        let plaintext = plaintext_int(val1, &params);
+        let ciphertext = encrypt_int(val2, keypair.as_ref().unwrap(), &params);
+
+        let sum = add_plaintext(ciphertext.as_ref().unwrap(), plaintext.as_ref().unwrap());
+
+        // Decrypt the sum
+        let plaintext_res = decrypt(keypair.pin_mut(), &sum);
+        let pt_u32 = get_element_int(&plaintext_res, 0);
+        let expected = val1 + val2;
+
+        assert_eq!(pt_u32, expected);
+    }
+
+    /// Tests multiplication of a plaintext to a ciphertext
+    #[test]
+    fn test_plaintext_multiplication() {
+        let mut rng = thread_rng();
+        let (params, mut keypair) = setup_fhe(1, 254);
+
+        // Multiply a plaintext to a ciphertext
+        let range = 0..(2u32.pow(16));
+        let val1 = rng.gen_range(range.clone());
+        let val2 = rng.gen_range(range.clone());
+
+        let plaintext = plaintext_int(val1, &params);
+        let ciphertext = encrypt_int(val2, keypair.as_ref().unwrap(), &params);
+
+        let product = mul_plaintext(ciphertext.as_ref().unwrap(), plaintext.as_ref().unwrap());
+
+        // Decrypt the product
+        let plaintext_res = decrypt(keypair.pin_mut(), &product);
+        let pt_u32 = get_element_int(&plaintext_res, 0);
+        let expected = val1 * val2;
+
+        assert_eq!(pt_u32, expected);
+    }
+
     /// Tests addition of two encrypted values
     #[test]
     fn test_encrypted_addition() {
@@ -87,8 +142,8 @@ mod test {
         let val1 = rng.next_u32() / 2;
         let val2 = rng.next_u32() / 2;
 
-        let cipher1 = encrypt_int(&params, &keypair, val1);
-        let cipher2 = encrypt_int(&params, &keypair, val2);
+        let cipher1 = encrypt_int(val1, &keypair, &params);
+        let cipher2 = encrypt_int(val2, &keypair, &params);
 
         let sum = add_ciphertexts(cipher1.as_ref().unwrap(), cipher2.as_ref().unwrap());
 
@@ -107,12 +162,12 @@ mod test {
         let (params, mut keypair) = setup_fhe(1, 254);
 
         // Multiply two ciphertexts; capped bit length to avoid overflow
-        let range = (0..(2u32.pow(16)));
+        let range = 0..(2u32.pow(16));
         let val1 = rng.gen_range(range.clone());
         let val2 = rng.gen_range(range.clone());
 
-        let cipher1 = encrypt_int(&params, &keypair, val1);
-        let cipher2 = encrypt_int(&params, &keypair, val2);
+        let cipher1 = encrypt_int(val1, &keypair, &params);
+        let cipher2 = encrypt_int(val2, &keypair, &params);
 
         let pk = get_pk(&keypair);
         let product = mul_ciphertexts(