diff --git a/common/fake_hardware.h b/common/fake_hardware.h
index 2a8e81d..30c0897 100644
--- a/common/fake_hardware.h
+++ b/common/fake_hardware.h
@@ -19,10 +19,12 @@
 
 #include <map>
 #include <string>
+#include <utility>
 
 #include <base/time/time.h>
 
 #include "update_engine/common/hardware_interface.h"
+#include "update_engine/common/utils.h"
 
 namespace chromeos_update_engine {
 
@@ -207,6 +209,18 @@
   bool GetIsRollbackPowerwashScheduled() const {
     return powerwash_scheduled_ && save_rollback_data_;
   }
+  std::string GetVersionForLogging(
+      const std::string& partition_name) const override {
+    return partition_timestamps_[partition_name];
+  }
+  void SetVersion(const std::string& partition_name, std::string timestamp) {
+    partition_timestamps_[partition_name] = std::move(timestamp);
+  }
+  bool IsPartitionUpdateValid(const std::string& partition_name,
+                              const std::string& new_version) const override {
+    const auto old_version = GetVersionForLogging(partition_name);
+    return utils::IsTimestampNewer(old_version, new_version);
+  }
 
  private:
   bool is_official_build_{true};
@@ -230,6 +244,7 @@
   int64_t build_timestamp_{0};
   bool first_active_omaha_ping_sent_{false};
   bool warm_reset_{false};
+  mutable std::map<std::string, std::string> partition_timestamps_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeHardware);
 };
diff --git a/common/hardware_interface.h b/common/hardware_interface.h
index 4f0305f..0fffbfb 100644
--- a/common/hardware_interface.h
+++ b/common/hardware_interface.h
@@ -142,6 +142,19 @@
   // If |warm_reset| is true, sets the warm reset to indicate a warm reset is
   // needed on the next reboot. Otherwise, clears the flag.
   virtual void SetWarmReset(bool warm_reset) = 0;
+
+  // Return the version/timestamp for partition `partition_name`.
+  // Don't make any assumption about the formatting of returned string.
+  // Only used for logging/debugging purposes.
+  virtual std::string GetVersionForLogging(
+      const std::string& partition_name) const = 0;
+
+  // Return true if and only if `new_version` is "newer" than the
+  // version number of partition `partition_name`. The notion of
+  // "newer" is defined by this function. Caller should not make
+  // any assumption about the underlying logic.
+  virtual bool IsPartitionUpdateValid(const std::string& partition_name,
+                                      const std::string& new_version) const = 0;
 };
 
 }  // namespace chromeos_update_engine
diff --git a/common/utils.cc b/common/utils.cc
index 3e3d830..bbb155f 100644
--- a/common/utils.cc
+++ b/common/utils.cc
@@ -820,7 +820,7 @@
   return base_code;
 }
 
-string StringVectorToString(const vector<string> &vec_str) {
+string StringVectorToString(const vector<string>& vec_str) {
   string str = "[";
   for (vector<string>::const_iterator i = vec_str.begin(); i != vec_str.end();
        ++i) {
@@ -849,7 +849,7 @@
                             encoded_hash.c_str());
 }
 
-bool ConvertToOmahaInstallDate(Time time, int *out_num_days) {
+bool ConvertToOmahaInstallDate(Time time, int* out_num_days) {
   time_t unix_time = time.ToTimeT();
   // Output of: date +"%s" --date="Jan 1, 2007 0:00 PST".
   const time_t kOmahaEpoch = 1167638400;
@@ -982,6 +982,29 @@
   return base::NumberToString(base::StringPieceHash()(str_to_convert));
 }
 
+static bool ParseTimestamp(const std::string& str, int64_t* out) {
+  if (!base::StringToInt64(str, out)) {
+    LOG(WARNING) << "Invalid timestamp: " << str;
+    return false;
+  }
+  return true;
+}
+
+bool IsTimestampNewer(const std::string& old_version,
+                      const std::string& new_version) {
+  if (old_version.empty() || new_version.empty()) {
+    LOG(WARNING)
+        << "One of old/new timestamp is empty, permit update anyway. Old: "
+        << old_version << " New: " << new_version;
+    return true;
+  }
+  int64_t old_ver = 0;
+  TEST_AND_RETURN_FALSE(ParseTimestamp(old_version, &old_ver));
+  int64_t new_ver = 0;
+  TEST_AND_RETURN_FALSE(ParseTimestamp(new_version, &new_ver));
+  return old_ver <= new_ver;
+}
+
 }  // namespace utils
 
 }  // namespace chromeos_update_engine
diff --git a/common/utils.h b/common/utils.h
index 23ac03d..5dfee3b 100644
--- a/common/utils.h
+++ b/common/utils.h
@@ -323,6 +323,12 @@
 // with |Excluder| as the exclusion name.
 std::string GetExclusionName(const std::string& str_to_convert);
 
+// Parse `old_version` and `new_version` as integer timestamps and
+// return true if `new_version` is larger/newer.
+// Returns true if either one is empty. Return false if
+bool IsTimestampNewer(const std::string& old_version,
+                      const std::string& new_version);
+
 }  // namespace utils
 
 // Utility class to close a file descriptor
diff --git a/common/utils_unittest.cc b/common/utils_unittest.cc
index ebcc548..37871d2 100644
--- a/common/utils_unittest.cc
+++ b/common/utils_unittest.cc
@@ -481,4 +481,12 @@
   IGNORE_EINTR(close(fd));
 }
 
+TEST(UtilsTest, ValidatePerPartitionTimestamp) {
+  ASSERT_FALSE(utils::IsTimestampNewer("10", "5"));
+  ASSERT_TRUE(utils::IsTimestampNewer("10", "11"));
+  ASSERT_FALSE(utils::IsTimestampNewer("10", "lol"));
+  ASSERT_FALSE(utils::IsTimestampNewer("lol", "ZZZ"));
+  ASSERT_TRUE(utils::IsTimestampNewer("10", ""));
+}
+
 }  // namespace chromeos_update_engine