diff --git a/binary.go b/binary.go
new file mode 100644
index 0000000..079d2eb
--- /dev/null
+++ b/binary.go
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2025 Fumiama Minamoto.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package blake2b
+
+import (
+	"bytes"
+	"encoding/binary"
+	"unsafe"
+)
+
+// MarshalBinary marshals current digest status into bytes.
+func (d *digest) MarshalBinary() ([]byte, error) {
+	buf := bytes.NewBuffer(make([]byte, 0, unsafe.Sizeof(*d)))
+	_ = binary.Write(buf, binary.BigEndian, &d.h)
+	_ = binary.Write(buf, binary.BigEndian, &d.t)
+	_ = binary.Write(buf, binary.BigEndian, &d.f)
+	_ = binary.Write(buf, binary.BigEndian, &d.x)
+	_ = binary.Write(buf, binary.BigEndian, int64(d.nx))
+	_ = binary.Write(buf, binary.BigEndian, &d.ih)
+	_ = binary.Write(buf, binary.BigEndian, &d.paddedKey)
+	if d.isKeyed {
+		buf.WriteByte(1)
+	} else {
+		buf.WriteByte(0)
+	}
+	buf.WriteByte(d.size)
+	if d.isLastNode {
+		buf.WriteByte(1)
+	} else {
+		buf.WriteByte(0)
+	}
+	return buf.Bytes(), nil
+}
+
+// UnmarshalBinary loads current digest status from bytes.
+func (d *digest) UnmarshalBinary(data []byte) error {
+	r := bytes.NewReader(data)
+	err := binary.Read(r, binary.BigEndian, &d.h)
+	if err != nil {
+		return err
+	}
+	err = binary.Read(r, binary.BigEndian, &d.t)
+	if err != nil {
+		return err
+	}
+	err = binary.Read(r, binary.BigEndian, &d.f)
+	if err != nil {
+		return err
+	}
+	err = binary.Read(r, binary.BigEndian, &d.x)
+	if err != nil {
+		return err
+	}
+	nx := int64(0)
+	err = binary.Read(r, binary.BigEndian, &nx)
+	if err != nil {
+		return err
+	}
+	d.nx = int(nx)
+	err = binary.Read(r, binary.BigEndian, &d.ih)
+	if err != nil {
+		return err
+	}
+	err = binary.Read(r, binary.BigEndian, &d.paddedKey)
+	if err != nil {
+		return err
+	}
+	b, err := r.ReadByte()
+	if err != nil {
+		return err
+	}
+	d.isKeyed = b != 0
+	d.size, err = r.ReadByte()
+	if err != nil {
+		return err
+	}
+	b, err = r.ReadByte()
+	if err != nil {
+		return err
+	}
+	d.isLastNode = b != 0
+	return nil
+}
diff --git a/binary_test.go b/binary_test.go
new file mode 100644
index 0000000..1153448
--- /dev/null
+++ b/binary_test.go
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2025 Fumiama Minamoto.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package blake2b
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding"
+	"encoding/hex"
+	"testing"
+)
+
+func TestBinaryMarshalUnmarshal256(t *testing.T) {
+	buf := make([]byte, 16384)
+	rand.Read(buf)
+	var (
+		exp [32]byte
+		got [32]byte
+	)
+	for i := 0; i < 16384; i++ {
+		h := New256()
+		_, err := h.Write(buf[:i])
+		if err != nil {
+			t.Fatal(err)
+		}
+		data, err := h.(encoding.BinaryMarshaler).MarshalBinary()
+		if err != nil {
+			t.Fatal(err)
+		}
+		newh := New256()
+		err = newh.(encoding.BinaryUnmarshaler).UnmarshalBinary(data)
+		if err != nil {
+			t.Fatal(err)
+		}
+		_, err = h.Write(buf[i:])
+		if err != nil {
+			t.Fatal(err)
+		}
+		_, err = newh.Write(buf[i:])
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !bytes.Equal(h.Sum(exp[:0]), newh.Sum(got[:0])) {
+			t.Fatal("Expect", hex.EncodeToString(exp[:]), "but got", hex.EncodeToString(got[:]))
+		}
+	}
+}
diff --git a/main/main.go b/main/main.go
index 5435e00..18b9ce9 100644
--- a/main/main.go
+++ b/main/main.go
@@ -1,3 +1,19 @@
+/*
+ * Copyright (c) 2022 Fumiama Minamoto.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package main
 
 import (