diff --git a/Android.bp b/Android.bp
index 8827d25..4432153 100644
--- a/Android.bp
+++ b/Android.bp
@@ -91,9 +91,11 @@
 
     srcs: [
         "Benchmark.cpp",
+        "CheckEncryption.cpp",
         "Devmapper.cpp",
         "EncryptInplace.cpp",
         "Ext4Crypt.cpp",
+        "FileDeviceUtils.cpp",
         "IdleMaint.cpp",
         "KeyBuffer.cpp",
         "KeyStorage.cpp",
diff --git a/CheckEncryption.cpp b/CheckEncryption.cpp
new file mode 100644
index 0000000..ffa3698
--- /dev/null
+++ b/CheckEncryption.cpp
@@ -0,0 +1,149 @@
+/*
+ * Copyright (C) 2017 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 "CheckEncryption.h"
+#include "FileDeviceUtils.h"
+#include "Utils.h"
+#include "VolumeManager.h"
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/unique_fd.h>
+#include <cutils/iosched_policy.h>
+#include <private/android_filesystem_config.h>
+
+#include <sstream>
+
+#include <sys/resource.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include <assert.h>
+#include <fcntl.h>
+#include <linux/fs.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+using android::base::unique_fd;
+
+using android::base::ReadFileToString;
+using android::base::WriteStringToFile;
+
+namespace android {
+namespace vold {
+
+constexpr uint32_t max_extents = 32;
+constexpr size_t bytecount = 8;
+constexpr int repeats = 256;
+
+bool check_file(const std::string& needle) {
+    LOG(DEBUG) << "checkEncryption check_file: " << needle;
+    auto haystack = android::vold::BlockDeviceForPath(needle);
+    if (haystack.empty()) {
+        LOG(ERROR) << "Failed to find device for path: " << needle;
+        return false;
+    }
+
+    std::string randombytes;
+    if (ReadRandomBytes(bytecount, randombytes) != 0) {
+        LOG(ERROR) << "Failed to read random bytes";
+        return false;
+    }
+    std::string randomhex;
+    StrToHex(randombytes, randomhex);
+    std::ostringstream os;
+    for (int i = 0; i < repeats; i++) os << randomhex;
+    auto towrite = os.str();
+
+    if (access(needle.c_str(), F_OK) == 0) {
+        if (unlink(needle.c_str()) != 0) {
+            PLOG(ERROR) << "Failed to unlink " << needle;
+            return false;
+        }
+    }
+    LOG(DEBUG) << "Writing to " << needle;
+    if (!WriteStringToFile(towrite, needle)) {
+        PLOG(ERROR) << "Failed to write " << needle;
+        return false;
+    }
+    sync();
+
+    unique_fd haystack_fd(open(haystack.c_str(), O_RDONLY | O_CLOEXEC));
+    if (haystack_fd.get() == -1) {
+        PLOG(ERROR) << "Failed to open " << haystack;
+        return false;
+    }
+
+    auto fiemap = PathFiemap(needle, max_extents);
+
+    std::string area;
+    for (uint32_t i = 0; i < fiemap->fm_mapped_extents; i++) {
+        auto xt = &(fiemap->fm_extents[i]);
+        LOG(DEBUG) << "Extent " << i << " at " << xt->fe_physical << " length " << xt->fe_length;
+        if (lseek64(haystack_fd.get(), xt->fe_physical, SEEK_SET) == -1) {
+            PLOG(ERROR) << "Failed lseek";
+            return false;
+        }
+        auto toread = xt->fe_length;
+        while (toread > 0) {
+            char buf[BUFSIZ];
+            size_t wlen =
+                static_cast<size_t>(std::min(static_cast<typeof(toread)>(sizeof(buf)), toread));
+            auto l = read(haystack_fd.get(), buf, wlen);
+            if (l < 1) {
+                PLOG(ERROR) << "Failed read";
+                if (errno != EINTR) {
+                    return false;
+                }
+            }
+            area.append(buf, l);
+            toread -= l;
+        }
+    }
+
+    LOG(DEBUG) << "Searching " << area.size() << " bytes of " << needle;
+    LOG(DEBUG) << "First position of blob: " << area.find(randomhex);
+    return true;
+}
+
+int CheckEncryption(const std::string& path) {
+    auto deNeedle(path);
+    deNeedle += "/misc";
+    if (android::vold::PrepareDir(deNeedle, 01771, AID_SYSTEM, AID_MISC)) {
+        return -1;
+    }
+    deNeedle += "/vold";
+    if (android::vold::PrepareDir(deNeedle, 0700, AID_ROOT, AID_ROOT)) {
+        return -1;
+    }
+    deNeedle += "/checkEncryption";
+
+    auto neNeedle(path);
+    neNeedle += "/unencrypted/checkEncryption";
+
+    check_file(deNeedle);
+    check_file(neNeedle);
+
+    return 0;
+}
+
+}  // namespace vold
+}  // namespace android
diff --git a/CheckEncryption.h b/CheckEncryption.h
new file mode 100644
index 0000000..158d886
--- /dev/null
+++ b/CheckEncryption.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#ifndef ANDROID_VOLD_CHECK_ENCRYPTION_H
+#define ANDROID_VOLD_CHECK_ENCRYPTION_H
+
+#include <string>
+
+namespace android {
+namespace vold {
+
+/* Check encryption of private volume mounted at the given path */
+int CheckEncryption(const std::string& path);
+
+}  // namespace vold
+}  // namespace android
+
+#endif
diff --git a/VoldNativeService.cpp b/VoldNativeService.cpp
index 0053478..d7a6576 100644
--- a/VoldNativeService.cpp
+++ b/VoldNativeService.cpp
@@ -17,11 +17,12 @@
 #define ATRACE_TAG ATRACE_TAG_PACKAGE_MANAGER
 
 #include "VoldNativeService.h"
-#include "VolumeManager.h"
 #include "Benchmark.h"
+#include "CheckEncryption.h"
+#include "IdleMaint.h"
 #include "MoveStorage.h"
 #include "Process.h"
-#include "IdleMaint.h"
+#include "VolumeManager.h"
 
 #include "cryptfs.h"
 #include "Ext4Crypt.h"
@@ -357,15 +358,9 @@
     return translate(vol->format(fsType));
 }
 
-binder::Status VoldNativeService::benchmark(const std::string& volId,
-        const android::sp<android::os::IVoldTaskListener>& listener) {
-    ENFORCE_UID(AID_SYSTEM);
-    CHECK_ARGUMENT_ID(volId);
-    ACQUIRE_LOCK;
-
-    std::string path;
+static binder::Status pathForVolId(const std::string& volId, std::string* path) {
     if (volId == "private" || volId == "null") {
-        path = "/data";
+        *path = "/data";
     } else {
         auto vol = VolumeManager::Instance()->findVolume(volId);
         if (vol == nullptr) {
@@ -377,12 +372,23 @@
         if (vol->getState() != VolumeBase::State::kMounted) {
             return error("Volume " + volId + " not mounted");
         }
-        path = vol->getPath();
+        *path = vol->getPath();
+        if (path->empty()) {
+            return error("Volume " + volId + " missing path");
+        }
     }
+    return ok();
+}
 
-    if (path.empty()) {
-        return error("Volume " + volId + " missing path");
-    }
+binder::Status VoldNativeService::benchmark(
+    const std::string& volId, const android::sp<android::os::IVoldTaskListener>& listener) {
+    ENFORCE_UID(AID_SYSTEM);
+    CHECK_ARGUMENT_ID(volId);
+    ACQUIRE_LOCK;
+
+    std::string path;
+    auto status = pathForVolId(volId, &path);
+    if (!status.isOk()) return status;
 
     std::thread([=]() {
         android::vold::Benchmark(path, listener);
@@ -390,6 +396,17 @@
     return ok();
 }
 
+binder::Status VoldNativeService::checkEncryption(const std::string& volId) {
+    ENFORCE_UID(AID_SYSTEM);
+    CHECK_ARGUMENT_ID(volId);
+    ACQUIRE_LOCK;
+
+    std::string path;
+    auto status = pathForVolId(volId, &path);
+    if (!status.isOk()) return status;
+    return translate(android::vold::CheckEncryption(path));
+}
+
 binder::Status VoldNativeService::moveStorage(const std::string& fromVolId,
         const std::string& toVolId, const android::sp<android::os::IVoldTaskListener>& listener) {
     ENFORCE_UID(AID_SYSTEM);
diff --git a/VoldNativeService.h b/VoldNativeService.h
index 8368bdc..7ca72e5 100644
--- a/VoldNativeService.h
+++ b/VoldNativeService.h
@@ -51,6 +51,7 @@
     binder::Status format(const std::string& volId, const std::string& fsType);
     binder::Status benchmark(const std::string& volId,
             const android::sp<android::os::IVoldTaskListener>& listener);
+    binder::Status checkEncryption(const std::string& volId);
 
     binder::Status moveStorage(const std::string& fromVolId, const std::string& toVolId,
             const android::sp<android::os::IVoldTaskListener>& listener);
diff --git a/binder/android/os/IVold.aidl b/binder/android/os/IVold.aidl
index 32d9b16..5d182c9 100644
--- a/binder/android/os/IVold.aidl
+++ b/binder/android/os/IVold.aidl
@@ -40,6 +40,7 @@
     void unmount(@utf8InCpp String volId);
     void format(@utf8InCpp String volId, @utf8InCpp String fsType);
     void benchmark(@utf8InCpp String volId, IVoldTaskListener listener);
+    void checkEncryption(@utf8InCpp String volId);
 
     void moveStorage(@utf8InCpp String fromVolId, @utf8InCpp String toVolId,
             IVoldTaskListener listener);
diff --git a/vdc.cpp b/vdc.cpp
index 761d035..19eb379 100644
--- a/vdc.cpp
+++ b/vdc.cpp
@@ -100,6 +100,8 @@
         checkStatus(vold->mountDefaultEncrypted());
     } else if (args[0] == "volume" && args[1] == "shutdown") {
         checkStatus(vold->shutdown());
+    } else if (args[0] == "cryptfs" && args[1] == "checkEncryption" && args.size() == 3) {
+        checkStatus(vold->checkEncryption(args[2]));
     } else {
         LOG(ERROR) << "Raw commands are no longer supported";
         exit(EINVAL);