diff --git a/apkverity/src/util.rs b/apkverity/src/util.rs
new file mode 100644
index 0000000..415e99b
--- /dev/null
+++ b/apkverity/src/util.rs
@@ -0,0 +1,68 @@
+/*
+ * 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.
+ */
+
+use anyhow::{bail, Result};
+use nix::sys::stat::FileStat;
+use std::fs;
+use std::fs::File;
+use std::os::unix::fs::FileTypeExt;
+use std::os::unix::io::AsRawFd;
+use std::path::Path;
+use std::thread;
+use std::time::{Duration, Instant};
+
+/// Returns when the file exists on the given `path` or timeout (1s) occurs.
+pub fn wait_for_path<P: AsRef<Path>>(path: P) -> Result<()> {
+    const TIMEOUT: Duration = Duration::from_secs(1);
+    const INTERVAL: Duration = Duration::from_millis(10);
+    let begin = Instant::now();
+    while !path.as_ref().exists() {
+        if begin.elapsed() > TIMEOUT {
+            bail!("{:?} not found. TIMEOUT.", path.as_ref());
+        }
+        thread::sleep(INTERVAL);
+    }
+    Ok(())
+}
+
+/// Returns hexadecimal reprentation of a given byte array.
+pub fn hexstring_from(s: &[u8]) -> String {
+    s.iter().map(|byte| format!("{:02x}", byte)).reduce(|i, j| i + &j).unwrap_or(String::new())
+}
+
+/// fstat that accepts a path rather than FD
+pub fn fstat(p: &Path) -> Result<FileStat> {
+    let f = File::open(p)?;
+    Ok(nix::sys::stat::fstat(f.as_raw_fd())?)
+}
+
+// From include/uapi/linux/fs.h
+const BLK: u8 = 0x12;
+const BLKGETSIZE64: u8 = 114;
+nix::ioctl_read!(_blkgetsize64, BLK, BLKGETSIZE64, libc::size_t);
+
+/// Gets the size of a block device
+pub fn blkgetsize64(p: &Path) -> Result<u64> {
+    let f = File::open(p)?;
+    if !f.metadata()?.file_type().is_block_device() {
+        bail!("{:?} is not a block device", p);
+    }
+    let mut size: usize = 0;
+    // SAFETY: kernel copies the return value out to `size`. The file is kept open until the end of
+    // this function.
+    unsafe { _blkgetsize64(f.as_raw_fd(), &mut size) }?;
+    Ok(size as u64)
+}