diff --git a/Cargo.toml b/Cargo.toml
index e80b73c..ce9bc0f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,3 +14,4 @@ wee_alloc = "0.4.4"
 default = [ "std" ]
 std = []
 debug = []
+experimental = []
diff --git a/circle.yml b/circle.yml
index c1c1c1f..402a919 100644
--- a/circle.yml
+++ b/circle.yml
@@ -30,3 +30,7 @@ jobs:
              cargo build --release --no-default-features
              cargo build --release --features debug
              cargo build --release --no-default-features --features debug
+             cargo build --release --features experimental
+             cargo build --release --no-default-features --features experimental
+             cargo build --release --features experimental,debug
+             cargo build --release --no-default-features --features experimental,debug
diff --git a/src/bignum.rs b/src/bignum.rs
new file mode 100644
index 0000000..6a8ab5a
--- /dev/null
+++ b/src/bignum.rs
@@ -0,0 +1,39 @@
+//! The bignum system library.
+
+use super::*;
+
+pub mod native {
+    extern "C" {
+        pub fn bignum_mul256(a: *const u32, b: *const u32, ret: *const u32);
+        pub fn bignum_umulmod256(a: *const u32, b: *const u32, modulo: *const u32, ret: *const u32);
+    }
+}
+
+pub fn mul256(a: &Uint256, b: &Uint256) -> Uint256 {
+    let mut ret = Uint256::default();
+
+    unsafe {
+        native::bignum_mul256(
+            a.bytes.as_ptr() as *const u32,
+            b.bytes.as_ptr() as *const u32,
+            ret.bytes.as_mut_ptr() as *const u32,
+        )
+    }
+
+    ret
+}
+
+pub fn umulmod256(a: &Uint256, b: &Uint256, modulo: &Uint256) -> Uint256 {
+    let mut ret = Uint256::default();
+
+    unsafe {
+        native::bignum_umulmod256(
+            a.bytes.as_ptr() as *const u32,
+            b.bytes.as_ptr() as *const u32,
+            modulo.bytes.as_ptr() as *const u32,
+            ret.bytes.as_mut_ptr() as *const u32,
+        )
+    }
+
+    ret
+}
diff --git a/src/lib.rs b/src/lib.rs
index 30cd945..145c623 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -31,6 +31,9 @@ mod utils;
 #[cfg(feature = "debug")]
 pub mod debug;
 
+#[cfg(feature = "experimental")]
+pub mod bignum;
+
 #[cfg(not(feature = "std"))]
 pub mod convert;