Add secret key -> polynomial array conversion

Sunscreen-tech · Feb 9, 2024 · 2118cfa · 2118cfa
1 parent 03b8561
commit 2118cfa
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Showing 4 changed files with 67 additions and 2 deletions.
diff --git a/native/src/seal/c/polyarray.cpp b/native/src/seal/c/polyarray.cpp
@@ -77,7 +77,32 @@ SEAL_C_FUNC PolynomialArray_CreateFromPublicKey(void *memoryPoolHandle, void *co
     }
 }
 
-SEAL_C_FUNC PolynomialArray_Copy(void *copy, void **poly_array) {
+SEAL_C_FUNC PolynomialArray_CreateFromSecretKey(
+    void *memoryPoolHandle, void *context, void *secret_key, void **poly_array)
+{
+    const SEALContext *ctx = FromVoid<SEALContext>(context);
+    IfNullRet(ctx, E_POINTER);
+
+    const SecretKey *sk = FromVoid<SecretKey>(secret_key);
+    IfNullRet(sk, E_POINTER);
+
+    IfNullRet(poly_array, E_POINTER);
+    unique_ptr<MemoryPoolHandle> handle = MemHandleFromVoid(memoryPoolHandle);
+
+    try
+    {
+        PolynomialArray *array = new PolynomialArray(*ctx, *sk, *handle);
+        *poly_array = array;
+        return S_OK;
+    }
+    catch (const invalid_argument &)
+    {
+        return E_INVALIDARG;
+    }
+}
+
+SEAL_C_FUNC PolynomialArray_Copy(void *copy, void **poly_array)
+{
     PolynomialArray *copyptr = FromVoid<PolynomialArray>(copy);
     IfNullRet(copyptr, E_POINTER);
     IfNullRet(poly_array, E_POINTER);

diff --git a/native/src/seal/c/polyarray.h b/native/src/seal/c/polyarray.h
@@ -9,6 +9,8 @@ SEAL_C_FUNC PolynomialArray_CreateFromCiphertext(void *memoryPoolHandle, void *c
 
 SEAL_C_FUNC PolynomialArray_CreateFromPublicKey(void *memoryPoolHandle, void *context, void *public_key, void **poly_array);
 
+SEAL_C_FUNC PolynomialArray_CreateFromSecretKey(void *memoryPoolHandle, void *context, void *secret_key, void **poly_array);
+
 SEAL_C_FUNC PolynomialArray_Copy(void *copy, void **poly_array);
 
 SEAL_C_FUNC PolynomialArray_Destroy(void *thisptr);

diff --git a/native/src/seal/polyarray.cpp b/native/src/seal/polyarray.cpp
@@ -82,11 +82,41 @@ namespace seal
         }
     }
 
+    PolynomialArray::PolynomialArray(
+        const SEALContext &context,
+        const SecretKey &secret_key,
+        MemoryPoolHandle pool
+    ) : PolynomialArray(pool) {
+
+        auto &pt = secret_key.data();
+        auto &parms = context.first_context_data()->parms();
+        auto &plain_modulus = parms.plain_modulus();
+        auto &coeff_modulus = parms.coeff_modulus();
+        auto coeff_modulus_size = coeff_modulus.size();
+        auto poly_modulus_degree = pt.coeff_count();
+
+        auto is_ntt_form = pt.is_ntt_form();
+        size_t coeff_count = parms.poly_modulus_degree();
+        auto &context_data = *context.get_context_data(parms.parms_id());
+        auto ntt_tables = context_data.small_ntt_tables();
+
+        reserve(1, poly_modulus_degree, {plain_modulus});
+
+        const auto data_ptr = pt.data();
+        insert_polynomial(0, data_ptr);
+
+        // Convert out of NTT form for each polynomial.
+        if (is_ntt_form) {
+            for (size_t i = 0; i < coeff_modulus_size; i++) {
+                inverse_ntt_negacyclic_harvey(get_polynomial(0) + i * coeff_count, ntt_tables[i]);
+            }
+        }
+    }
+
     PolynomialArray::PolynomialArray(const PolynomialArray &copy): PolynomialArray(copy.pool_) {
         // These parameters in the result object are internally stored once
         // reserve is called.
         auto poly_size = copy.poly_size();
-        auto coeff_modulus_size = copy.coeff_modulus_size();
         auto coeff_modulus = copy.coeff_modulus_;
         auto poly_modulus_degree = copy.poly_modulus_degree();
 

diff --git a/native/src/seal/polyarray.h b/native/src/seal/polyarray.h
@@ -4,6 +4,7 @@
 #include "seal/ciphertext.h"
 #include "seal/memorymanager.h"
 #include "seal/publickey.h"
+#include "seal/secretkey.h"
 #include <stdexcept>
 
 using namespace seal::util;
@@ -45,6 +46,13 @@ namespace seal
                     const SEALContext &context, const PublicKey &public_key, MemoryPoolHandle pool
                 );
 
+                /**
+                Create a PolynomialArray from a secret key.
+                */
+                PolynomialArray(
+                    const SEALContext &context, const SecretKey &secret_key, MemoryPoolHandle pool
+                );
+
                 /**
                 Creates a new ciphertext by copying a given one.