diff --git a/microdroid_manager/src/instance.rs b/microdroid_manager/src/instance.rs
index 73983a7..e50f4a8 100644
--- a/microdroid_manager/src/instance.rs
+++ b/microdroid_manager/src/instance.rs
@@ -328,5 +328,6 @@
 #[derive(Debug, Serialize, Deserialize, PartialEq)]
 pub struct ApexData {
     pub name: String,
-    pub pubkey: Vec<u8>,
+    pub public_key: Vec<u8>,
+    pub root_digest: Vec<u8>,
 }
diff --git a/microdroid_manager/src/main.rs b/microdroid_manager/src/main.rs
index 204feab..8555892 100644
--- a/microdroid_manager/src/main.rs
+++ b/microdroid_manager/src/main.rs
@@ -162,14 +162,15 @@
     // Start apkdmverity and wait for the dm-verify block
     system_properties::write("ctl.start", "apkdmverity")?;
 
-    // While waiting for apkdmverity to mount APK, gathers APEX pubkeys from payload.
+    // While waiting for apkdmverity to mount APK, gathers public keys and root digests from
+    // APEX payload.
     let apex_data_from_payload = get_apex_data_from_payload(metadata)?;
     if let Some(saved_data) = saved_data.map(|d| &d.apex_data) {
-        // For APEX payload, we don't support updating their pubkeys
+        // We don't support APEX updates. (assuming that update will change root digest)
         ensure!(saved_data == &apex_data_from_payload, "APEX payloads has changed.");
         let apex_metadata = to_metadata(&apex_data_from_payload);
-        // Pass metadata(with pubkeys) to apexd so that it uses the passed metadata
-        // instead of the default one (/dev/block/by-name/payload-metadata)
+        // Pass metadata(with public keys and root digests) to apexd so that it uses the passed
+        // metadata instead of the default one (/dev/block/by-name/payload-metadata)
         OpenOptions::new()
             .create_new(true)
             .write(true)
diff --git a/microdroid_manager/src/payload.rs b/microdroid_manager/src/payload.rs
index bf9d9f9..8ec6f74 100644
--- a/microdroid_manager/src/payload.rs
+++ b/microdroid_manager/src/payload.rs
@@ -17,14 +17,11 @@
 use crate::instance::ApexData;
 use crate::ioutil::wait_for_file;
 use anyhow::Result;
+use apex::verify;
 use log::info;
 use microdroid_metadata::{read_metadata, ApexPayload, Metadata};
-use std::fs::File;
-use std::io::Read;
 use std::time::Duration;
-use zip::ZipArchive;
 
-const APEX_PUBKEY_ENTRY: &str = "apex_pubkey";
 const PAYLOAD_METADATA_PATH: &str = "/dev/block/by-name/payload-metadata";
 const WAIT_TIMEOUT: Duration = Duration::from_secs(10);
 
@@ -35,29 +32,20 @@
     read_metadata(file)
 }
 
-/// Loads (name, pubkey) from payload APEXes
+/// Loads (name, public_key, root_digest) from payload APEXes
 pub fn get_apex_data_from_payload(metadata: &Metadata) -> Result<Vec<ApexData>> {
     metadata
         .apexes
         .iter()
         .map(|apex| {
             let name = apex.name.clone();
-            let partition = format!("/dev/block/by-name/{}", apex.partition_name);
-            let pubkey = get_pubkey_from_apex(&partition)?;
-            Ok(ApexData { name, pubkey })
+            let apex_path = format!("/dev/block/by-name/{}", apex.partition_name);
+            let result = verify(&apex_path)?;
+            Ok(ApexData { name, public_key: result.public_key, root_digest: result.root_digest })
         })
         .collect()
 }
 
-fn get_pubkey_from_apex(path: &str) -> Result<Vec<u8>> {
-    let f = File::open(path)?;
-    let mut z = ZipArchive::new(f)?;
-    let mut pubkey_file = z.by_name(APEX_PUBKEY_ENTRY)?;
-    let mut pubkey = Vec::new();
-    pubkey_file.read_to_end(&mut pubkey)?;
-    Ok(pubkey)
-}
-
 /// Convert vector of ApexData into Metadata
 pub fn to_metadata(apex_data: &[ApexData]) -> Metadata {
     Metadata {
@@ -65,10 +53,13 @@
             .iter()
             .map(|data| ApexPayload {
                 name: data.name.clone(),
-                public_key: data.pubkey.clone(),
+                public_key: data.public_key.clone(),
+                root_digest: data.root_digest.clone(),
                 ..Default::default()
             })
             .collect(),
         ..Default::default()
     }
 }
+
+mod apex;
diff --git a/microdroid_manager/src/payload/apex.rs b/microdroid_manager/src/payload/apex.rs
new file mode 100644
index 0000000..24c4f05
--- /dev/null
+++ b/microdroid_manager/src/payload/apex.rs
@@ -0,0 +1,225 @@
+// Copyright 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.
+
+//! Routines for handling APEX payload
+
+use anyhow::{anyhow, ensure, Result};
+use avb_bindgen::*;
+use std::ffi::{c_void, CStr};
+use std::fs::File;
+use std::io::{Read, Seek, SeekFrom};
+use std::mem::{size_of, zeroed};
+use std::ops::Deref;
+use std::ptr::null_mut;
+use std::slice::{from_raw_parts, from_raw_parts_mut};
+use zip::ZipArchive;
+
+const APEX_PUBKEY_ENTRY: &str = "apex_pubkey";
+const APEX_PAYLOAD_ENTRY: &str = "apex_payload.img";
+
+/// Verification result holds public key and root digest of apex_payload.img
+pub struct ApexVerificationResult {
+    pub public_key: Vec<u8>,
+    pub root_digest: Vec<u8>,
+}
+
+/// Verify APEX payload by AVB verification and return public key and root digest
+pub fn verify(path: &str) -> Result<ApexVerificationResult> {
+    let apex_file = File::open(path)?;
+    let (public_key, image_offset, image_size) = get_public_key_and_image_info(&apex_file)?;
+    let root_digest = verify_vbmeta(apex_file, image_offset, image_size, &public_key)?;
+    Ok(ApexVerificationResult { public_key, root_digest })
+}
+
+fn get_public_key_and_image_info(apex_file: &File) -> Result<(Vec<u8>, u64, u64)> {
+    let mut z = ZipArchive::new(apex_file)?;
+
+    let mut public_key = Vec::new();
+    z.by_name(APEX_PUBKEY_ENTRY)?.read_to_end(&mut public_key)?;
+
+    let (image_offset, image_size) =
+        z.by_name(APEX_PAYLOAD_ENTRY).map(|f| (f.data_start(), f.size()))?;
+
+    Ok((public_key, image_offset, image_size))
+}
+
+// Manual addition of a missing enum
+#[allow(non_camel_case_types, dead_code)]
+#[repr(u8)]
+enum AvbDescriptorTag {
+    AVB_DESCRIPTOR_TAG_PROPERTY = 0,
+    AVB_DESCRIPTOR_TAG_HASHTREE,
+    AVB_DESCRIPTOR_TAG_HASH,
+    AVB_DESCRIPTOR_TAG_KERNEL_CMDLINE,
+    AVB_DESCRIPTOR_TAG_CHAIN_PARTITION,
+}
+
+const FOOTER_SIZE: usize = size_of::<AvbFooter>();
+const HASHTREE_DESCRIPTOR_SIZE: usize = size_of::<AvbHashtreeDescriptor>();
+
+/// Verify VBmeta image and return root digest
+fn verify_vbmeta<R: Read + Seek>(
+    image: R,
+    offset: u64,
+    size: u64,
+    public_key: &[u8],
+) -> Result<Vec<u8>> {
+    let vbmeta = VbMeta::from(image, offset, size)?;
+    vbmeta.verify(public_key)?;
+    for &descriptor in vbmeta.descriptors()?.iter() {
+        if let Ok(hashtree_descriptor) = HashtreeDescriptor::from(descriptor) {
+            return hashtree_descriptor.root_digest();
+        }
+    }
+    Err(anyhow!("HashtreeDescriptor is not found."))
+}
+
+struct VbMeta {
+    data: Vec<u8>,
+}
+
+impl VbMeta {
+    // Read a VbMeta data from a given image
+    fn from<R: Read + Seek>(mut image: R, offset: u64, size: u64) -> Result<VbMeta> {
+        // Get AvbFooter first
+        image.seek(SeekFrom::Start(offset + size - FOOTER_SIZE as u64))?;
+        // SAFETY: AvbDescriptor is a "repr(C,packed)" struct from bindgen
+        let mut footer: AvbFooter = unsafe { zeroed() };
+        // SAFETY: safe to read because of seek(-FOOTER_SIZE) above
+        unsafe {
+            let footer_slice = from_raw_parts_mut(&mut footer as *mut _ as *mut u8, FOOTER_SIZE);
+            image.read_exact(footer_slice)?;
+            ensure!(avb_footer_validate_and_byteswap(&footer, &mut footer));
+        }
+        // Get VbMeta block
+        image.seek(SeekFrom::Start(offset + footer.vbmeta_offset))?;
+        let vbmeta_size = footer.vbmeta_size as usize;
+        let mut data = vec![0u8; vbmeta_size];
+        image.read_exact(&mut data)?;
+        Ok(VbMeta { data })
+    }
+    // Verify VbMeta image. Its enclosed public key should match with a given public key.
+    fn verify(&self, outer_public_key: &[u8]) -> Result<()> {
+        // SAFETY: self.data points to a valid VBMeta data and avb_vbmeta_image_verify should work fine
+        // with it
+        let public_key = unsafe {
+            let mut pk_ptr: *const u8 = null_mut();
+            let mut pk_len: usize = 0;
+            let res = avb_vbmeta_image_verify(
+                self.data.as_ptr(),
+                self.data.len(),
+                &mut pk_ptr,
+                &mut pk_len,
+            );
+            ensure!(
+                res == AvbVBMetaVerifyResult_AVB_VBMETA_VERIFY_RESULT_OK,
+                CStr::from_ptr(avb_vbmeta_verify_result_to_string(res))
+                    .to_string_lossy()
+                    .into_owned()
+            );
+            from_raw_parts(pk_ptr, pk_len)
+        };
+
+        ensure!(public_key == outer_public_key, "Public key mismatch with a given one.");
+        Ok(())
+    }
+    // Return a slice of AvbDescriptor pointers
+    fn descriptors(&self) -> Result<Descriptors> {
+        let mut num: usize = 0;
+        // SAFETY: ptr will be freed by Descriptor.
+        Ok(unsafe {
+            let ptr = avb_descriptor_get_all(self.data.as_ptr(), self.data.len(), &mut num);
+            ensure!(!ptr.is_null(), "VbMeta has no descriptors.");
+            let all = from_raw_parts(ptr, num);
+            Descriptors { ptr, all }
+        })
+    }
+}
+
+struct HashtreeDescriptor {
+    ptr: *const u8,
+    inner: AvbHashtreeDescriptor,
+}
+
+impl HashtreeDescriptor {
+    fn from(descriptor: *const AvbDescriptor) -> Result<HashtreeDescriptor> {
+        // SAFETY: AvbDescriptor is a "repr(C,packed)" struct from bindgen
+        let mut desc: AvbDescriptor = unsafe { zeroed() };
+        // SAFETY: both points to valid AvbDescriptor pointers
+        unsafe {
+            ensure!(avb_descriptor_validate_and_byteswap(descriptor, &mut desc));
+        }
+        ensure!({ desc.tag } == AvbDescriptorTag::AVB_DESCRIPTOR_TAG_HASHTREE as u64);
+        // SAFETY: AvbHashtreeDescriptor is a "repr(C, packed)" struct from bindgen
+        let mut hashtree_descriptor: AvbHashtreeDescriptor = unsafe { zeroed() };
+        // SAFETY: With tag == AVB_DESCRIPTOR_TAG_HASHTREE, descriptor should point to
+        // a AvbHashtreeDescriptor.
+        unsafe {
+            ensure!(avb_hashtree_descriptor_validate_and_byteswap(
+                descriptor as *const AvbHashtreeDescriptor,
+                &mut hashtree_descriptor,
+            ));
+        }
+        Ok(Self { ptr: descriptor as *const u8, inner: hashtree_descriptor })
+    }
+    fn root_digest(&self) -> Result<Vec<u8>> {
+        // SAFETY: digest_ptr should point to a valid buffer of root_digest_len
+        let root_digest = unsafe {
+            let digest_ptr = self.ptr.offset(
+                HASHTREE_DESCRIPTOR_SIZE as isize
+                    + self.inner.partition_name_len as isize
+                    + self.inner.salt_len as isize,
+            );
+            from_raw_parts(digest_ptr, self.inner.root_digest_len as usize)
+        };
+        Ok(root_digest.to_owned())
+    }
+}
+
+// Wraps pointer to a heap-allocated array of AvbDescriptor pointers
+struct Descriptors<'a> {
+    ptr: *mut *const AvbDescriptor,
+    all: &'a [*const AvbDescriptor],
+}
+
+// Wrapped pointer should be freed with avb_free.
+impl Drop for Descriptors<'_> {
+    fn drop(&mut self) {
+        // SAFETY: ptr is allocated by avb_descriptor_get_all
+        unsafe { avb_free(self.ptr as *mut c_void) }
+    }
+}
+
+impl<'a> Deref for Descriptors<'a> {
+    type Target = &'a [*const AvbDescriptor];
+    fn deref(&self) -> &Self::Target {
+        &self.all
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    fn to_hex_string(buf: &[u8]) -> String {
+        buf.iter().map(|b| format!("{:02x}", b)).collect()
+    }
+    #[test]
+    fn test_open_apex() {
+        let res = verify("tests/data/test.apex").unwrap();
+        assert_eq!(
+            to_hex_string(&res.root_digest),
+            "fe11ab17da0a3a738b54bdc3a13f6139cbdf91ec32f001f8d4bbbf8938e04e39"
+        );
+    }
+}