diff --git a/apex/Android.bp b/apex/Android.bp
index 41d2f62..9c201b4 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -43,8 +43,9 @@
         },
     },
     binaries: [
-        "mk_cdisk",
         "fd_server",
+        "mk_cdisk",
+        "mk_microdroid_signature",
         "virtmanager",
         "vm",
     ],
diff --git a/microdroid/signature/Android.bp b/microdroid/signature/Android.bp
new file mode 100644
index 0000000..63c2128
--- /dev/null
+++ b/microdroid/signature/Android.bp
@@ -0,0 +1,49 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_defaults {
+    name: "microdroid_signature_default",
+    host_supported: true,
+    srcs: [
+        "microdroid_signature.proto",
+        "signature.cc",
+    ],
+    shared_libs: [
+        "libbase",
+        "liblog",
+    ],
+    export_include_dirs: ["include"],
+}
+
+cc_library_static {
+    name: "lib_microdroid_signature_proto_lite",
+    recovery_available: true,
+    proto: {
+        export_proto_headers: true,
+        type: "lite",
+    },
+    defaults: ["microdroid_signature_default"],
+    apex_available: [
+        "com.android.virt",
+    ],
+}
+
+cc_binary {
+    name: "mk_microdroid_signature",
+    srcs: [
+        "mk_microdroid_signature.cc",
+    ],
+    shared_libs: [
+        "libbase",
+        "liblog",
+    ],
+    static_libs: [
+        "lib_microdroid_signature_proto_lite",
+        "libjsoncpp",
+        "libprotobuf-cpp-lite",
+    ],
+    apex_available: [
+        "com.android.virt",
+    ],
+}
diff --git a/microdroid/signature/README.md b/microdroid/signature/README.md
index 526f7a8..4f434ee 100644
--- a/microdroid/signature/README.md
+++ b/microdroid/signature/README.md
@@ -13,3 +13,44 @@
 |--------|------|----------------------------------------------------------------|
 | 0      | 4    | Header. unsigned int32: body length(L) in big endian           |
 | 4      | L    | Body. A protobuf message. [schema](microdroid_signature.proto) |
+
+## How to Create
+
+For testing purpose, use `mk_microdroid_signature` to create a Microdroid Signature.
+
+```
+$ cat signature_config.json
+{
+  "apexes": [
+    {
+      "name": "com.my.hello",
+      "path": "hello.apex"
+    }
+  ]
+}
+$ adb push signature_config.json hello.apex /data/local/tmp/
+$ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/mk_microdroid_signature signature_config.json signature
+```
+
+Then, pass the signature as the first partition of the payload disk image.
+
+```
+$ cat payload_cdisk.json
+{
+  "partitions": [
+    {
+      "label": "signature",
+      "path": "signature"
+    },
+    {
+      "label": "com.my.hello",
+      "path": "hello.apex"
+    }
+  ]
+}
+$ adb push payload_cdisk.json /data/local/tmp/
+$ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/mk_cdisk payload_cdisk.json payload.img
+$ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/crosvm .... --disk=payload.img'
+```
+
+In the future, [VirtManager](../../virtmanager) will handle these stuffs.
\ No newline at end of file
diff --git a/microdroid/signature/include/microdroid/signature.h b/microdroid/signature/include/microdroid/signature.h
new file mode 100644
index 0000000..abacd6e
--- /dev/null
+++ b/microdroid/signature/include/microdroid/signature.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include <android-base/result.h>
+#include <microdroid_signature.pb.h>
+
+#include <iostream>
+#include <string>
+
+namespace android {
+namespace microdroid {
+
+base::Result<MicrodroidSignature> ReadMicrodroidSignature(const std::string& path);
+
+base::Result<void> WriteMicrodroidSignature(const MicrodroidSignature& signature,
+                                            std::ostream& out);
+
+} // namespace microdroid
+} // namespace android
diff --git a/microdroid/signature/mk_microdroid_signature.cc b/microdroid/signature/mk_microdroid_signature.cc
new file mode 100644
index 0000000..d5cb1a5
--- /dev/null
+++ b/microdroid/signature/mk_microdroid_signature.cc
@@ -0,0 +1,141 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <fstream>
+#include <iostream>
+#include <string>
+
+#include <android-base/file.h>
+#include <android-base/result.h>
+#include <json/json.h>
+
+#include "microdroid/signature.h"
+
+using android::base::Dirname;
+using android::base::ErrnoError;
+using android::base::Error;
+using android::base::Result;
+using android::microdroid::MicrodroidSignature;
+using android::microdroid::WriteMicrodroidSignature;
+
+Result<uint32_t> GetFileSize(const std::string& path) {
+    struct stat st;
+    if (lstat(path.c_str(), &st) == -1) {
+        return ErrnoError() << "Can't lstat " << path;
+    }
+    return static_cast<uint32_t>(st.st_size);
+}
+
+// config JSON schema:
+// {
+//   "apexes": [
+//     {
+//       "name": string,       // the apex name
+//       "path": string,       // the path to the apex file
+//                             // absolute or relative to the config file
+//       "publicKey": string,  // optional
+//       "rootDigest": string, // optional
+//     }
+//   ]
+// }
+
+Result<MicrodroidSignature> LoadConfig(const std::string& config_file) {
+    MicrodroidSignature signature;
+    signature.set_version(1);
+
+    const std::string dirname = Dirname(config_file);
+    std::ifstream in(config_file);
+    Json::CharReaderBuilder builder;
+    Json::Value root;
+    Json::String errs;
+    if (!parseFromStream(builder, in, &root, &errs)) {
+        return Error() << "bad config: " << errs;
+    }
+
+    for (const Json::Value& apex : root["apexes"]) {
+        auto apex_signature = signature.add_apexes();
+
+        Json::Value name = apex["name"];
+        Json::Value path = apex["path"];
+        Json::Value publicKey = apex["publicKey"];
+        Json::Value rootDigest = apex["rootDigest"];
+
+        if (name.isString()) {
+            apex_signature->set_name(name.asString());
+        } else {
+            return Error() << "bad config: apexes.name should be a string: " << path;
+        }
+
+        if (path.isString()) {
+            std::string apex_path = path.asString();
+
+            // resolve path with the config_file's dirname if not absolute
+            bool is_absolute = !apex_path.empty() && apex_path[0] == '/';
+            if (!is_absolute) {
+                apex_path = dirname + "/" + apex_path;
+            }
+
+            auto file_size = GetFileSize(apex_path);
+            if (!file_size.ok()) {
+                return Error() << "I/O error: " << file_size.error();
+            }
+            apex_signature->set_size(file_size.value());
+        } else {
+            return Error() << "bad config: apexes.path should be a string: " << path;
+        }
+
+        if (publicKey.isString()) {
+            apex_signature->set_publickey(publicKey.asString());
+        } else if (!publicKey.isNull()) {
+            return Error() << "bad config: apexes.publicKey should be a string or null: "
+                           << publicKey;
+        }
+
+        if (rootDigest.isString()) {
+            apex_signature->set_rootdigest(rootDigest.asString());
+        } else if (!rootDigest.isNull()) {
+            return Error() << "bad config: apexes.rootDigest should be a string or null: "
+                           << rootDigest;
+        }
+    }
+
+    return signature;
+}
+
+int main(int argc, char** argv) {
+    if (argc != 3) {
+        std::cerr << "Usage: " << argv[0] << " <config> <output>\n";
+        return 1;
+    }
+
+    auto config = LoadConfig(argv[1]);
+    if (!config.ok()) {
+        std::cerr << config.error() << '\n';
+        return 1;
+    }
+
+    std::ofstream out(argv[2]);
+    auto result = WriteMicrodroidSignature(*config, out);
+    if (!result.ok()) {
+        std::cerr << result.error() << '\n';
+        return 1;
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/microdroid/signature/signature.cc b/microdroid/signature/signature.cc
new file mode 100644
index 0000000..446159e
--- /dev/null
+++ b/microdroid/signature/signature.cc
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "microdroid/signature.h"
+
+#include <android-base/endian.h>
+#include <android-base/file.h>
+
+using android::base::ErrnoError;
+using android::base::Error;
+using android::base::Result;
+
+namespace android {
+namespace microdroid {
+
+Result<MicrodroidSignature> ReadMicrodroidSignature(const std::string& path) {
+    std::string content;
+    if (!base::ReadFileToString(path, &content)) {
+        return ErrnoError() << "Failed to read " << path;
+    }
+
+    // read length prefix (4-byte, big-endian)
+    uint32_t size;
+    const size_t length_prefix_bytes = sizeof(size);
+    if (content.size() < length_prefix_bytes) {
+        return Error() << "Invalid signature: size == " << content.size();
+    }
+    size = be32toh(*reinterpret_cast<uint32_t*>(content.data()));
+    if (content.size() < length_prefix_bytes + size) {
+        return Error() << "Invalid signature: size(" << size << ") mimatches to the content size("
+                       << content.size() - length_prefix_bytes << ")";
+    }
+    content = content.substr(length_prefix_bytes, size);
+
+    // parse content
+    MicrodroidSignature signature;
+    if (!signature.ParseFromString(content)) {
+        return Error() << "Can't parse MicrodroidSignature from " << path;
+    }
+    return signature;
+}
+
+Result<void> WriteMicrodroidSignature(const MicrodroidSignature& signature, std::ostream& out) {
+    // prepare content
+    std::string content;
+    if (!signature.SerializeToString(&content)) {
+        return Error() << "Failed to write protobuf.";
+    }
+
+    // write length prefix (4-byte, big-endian)
+    uint32_t size = htobe32(static_cast<uint32_t>(content.size()));
+    out.write(reinterpret_cast<const char*>(&size), sizeof(size));
+
+    // write content
+    out << content;
+
+    return {};
+}
+
+} // namespace microdroid
+} // namespace android
\ No newline at end of file