1 files changed, 34 insertions, 0 deletions
diff --git a/src/lib/pubkey/ed25519/ed25519_internal.h b/src/lib/pubkey/ed25519/ed25519_internal.h
index cb75e8540..0efeee6d7 100644
--- a/src/lib/pubkey/ed25519/ed25519_internal.h
+++ b/src/lib/pubkey/ed25519/ed25519_internal.h
@@ -28,6 +28,40 @@ inline uint64_t load_4(const uint8_t* in)
    return load_le<uint32_t>(in, 0);
    }
 
+template<size_t S, int64_t MUL=1>
+inline void carry(int64_t& h0, int64_t& h1)
+   {
+   static_assert(S > 0 && S < 64, "Shift in range");
+
+   const int64_t X1 = (static_cast<int64_t>(1) << S);
+   const int64_t X2 = (static_cast<int64_t>(1) << (S - 1));
+   int64_t c = (h0 + X2)  >> S;
+   h1 += c * MUL;
+   h0 -= c * X1;
+   }
+
+template<size_t S>
+inline void carry0(int64_t& h0, int64_t& h1)
+   {
+   static_assert(S > 0 && S < 64, "Shift in range");
+
+   const int64_t X1 = (static_cast<int64_t>(1) << S);
+   int64_t c = h0 >> S;
+   h1 += c;
+   h0 -= c * X1;
+   }
+
+template<size_t S>
+inline void carry0(int32_t& h0, int32_t& h1)
+   {
+   static_assert(S > 0 && S < 32, "Shift in range");
+
+   const int32_t X1 = (static_cast<int64_t>(1) << S);
+   int32_t c = h0 >> S;
+   h1 += c;
+   h0 -= c * X1;
+   }
+
 /*
 ge means group element.