diff --git a/update_verifier/update_verifier.cpp b/update_verifier/update_verifier.cpp
index be70cec..f89eb5a 100644
--- a/update_verifier/update_verifier.cpp
+++ b/update_verifier/update_verifier.cpp
@@ -22,24 +22,120 @@
  * It relies on dm-verity to capture any corruption on the partitions being
  * verified. dm-verity must be in enforcing mode, so that it will reboot the
  * device on dm-verity failures. When that happens, the bootloader should
- * mark the slot as unbootable and stops trying. We should never see a device
- * started in dm-verity logging mode but with isSlotMarkedSuccessful equals to
- * 0.
+ * mark the slot as unbootable and stops trying. Other dm-verity modes (
+ * for example, veritymode=EIO) are not accepted and simply lead to a
+ * verification failure.
  *
  * The current slot will be marked as having booted successfully if the
  * verifier reaches the end after the verification.
  *
- * TODO: The actual verification part will be added later after we have the
- * A/B OTA package format in place.
  */
 
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
 #include <string.h>
 
-#include <hardware/boot_control.h>
+#include <string>
+#include <vector>
 
+#include <android-base/file.h>
+#include <android-base/parseint.h>
+#include <android-base/strings.h>
+#include <android-base/unique_fd.h>
+#include <cutils/properties.h>
+#include <hardware/boot_control.h>
 #define LOG_TAG       "update_verifier"
 #include <log/log.h>
 
+constexpr auto CARE_MAP_FILE = "/data/ota_package/care_map.txt";
+constexpr int BLOCKSIZE = 4096;
+
+static bool read_blocks(const std::string& blk_device_prefix, const std::string& range_str) {
+    char slot_suffix[PROPERTY_VALUE_MAX];
+    property_get("ro.boot.slot_suffix", slot_suffix, "");
+    std::string blk_device = blk_device_prefix + std::string(slot_suffix);
+    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(blk_device.c_str(), O_RDONLY)));
+    if (fd.get() == -1) {
+        SLOGE("Error reading partition %s: %s\n", blk_device.c_str(), strerror(errno));
+        return false;
+    }
+
+    // For block range string, first integer 'count' equals 2 * total number of valid ranges,
+    // followed by 'count' number comma separated integers. Every two integers reprensent a
+    // block range with the first number included in range but second number not included.
+    // For example '4,64536,65343,74149,74150' represents: [64536,65343) and [74149,74150).
+    std::vector<std::string> ranges = android::base::Split(range_str, ",");
+    size_t range_count;
+    bool status = android::base::ParseUint(ranges[0].c_str(), &range_count);
+    if (!status || (range_count == 0) || (range_count % 2 != 0) ||
+            (range_count != ranges.size()-1)) {
+        SLOGE("Error in parsing range string.\n");
+        return false;
+    }
+
+    size_t blk_count = 0;
+    for (size_t i = 1; i < ranges.size(); i += 2) {
+        unsigned int range_start, range_end;
+        bool parse_status = android::base::ParseUint(ranges[i].c_str(), &range_start);
+        parse_status = parse_status && android::base::ParseUint(ranges[i+1].c_str(), &range_end);
+        if (!parse_status || range_start >= range_end) {
+            SLOGE("Invalid range pair %s, %s.\n", ranges[i].c_str(), ranges[i+1].c_str());
+            return false;
+        }
+
+        if (lseek64(fd.get(), static_cast<off64_t>(range_start) * BLOCKSIZE, SEEK_SET) == -1) {
+            SLOGE("lseek to %u failed: %s.\n", range_start, strerror(errno));
+            return false;
+        }
+
+        size_t size = (range_end - range_start) * BLOCKSIZE;
+        std::vector<uint8_t> buf(size);
+        if (!android::base::ReadFully(fd.get(), buf.data(), size)) {
+            SLOGE("Failed to read blocks %u to %u: %s.\n", range_start, range_end,
+                  strerror(errno));
+            return false;
+        }
+        blk_count += (range_end - range_start);
+    }
+
+    SLOGI("Finished reading %zu blocks on %s.\n", blk_count, blk_device.c_str());
+    return true;
+}
+
+static bool verify_image(const std::string& care_map_name) {
+    android::base::unique_fd care_map_fd(TEMP_FAILURE_RETRY(open(care_map_name.c_str(), O_RDONLY)));
+    if (care_map_fd.get() == -1) {
+        SLOGE("Care map %s not found.\n", care_map_name.c_str());
+        return false;
+    }
+    // Care map file has four lines (two lines if vendor partition is not present):
+    // First line has the block device name, e.g./dev/block/.../by-name/system.
+    // Second line holds all ranges of blocks to verify.
+    // The next two lines have the same format but for vendor partition.
+    std::string file_content;
+    if (!android::base::ReadFdToString(care_map_fd.get(), &file_content)) {
+        SLOGE("Error reading care map contents to string.\n");
+        return false;
+    }
+
+    std::vector<std::string> lines;
+    lines = android::base::Split(android::base::Trim(file_content), "\n");
+    if (lines.size() != 2 && lines.size() != 4) {
+        SLOGE("Invalid lines in care_map: found %zu lines, expecting 2 or 4 lines.\n",
+              lines.size());
+        return false;
+    }
+
+    for (size_t i = 0; i < lines.size(); i += 2) {
+        if (!read_blocks(lines[i], lines[i+1])) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
 int main(int argc, char** argv) {
   for (int i = 1; i < argc; i++) {
     SLOGI("Started with arg %d: %s\n", i, argv[i]);
@@ -58,15 +154,24 @@
   unsigned current_slot = module->getCurrentSlot(module);
   int is_successful= module->isSlotMarkedSuccessful(module, current_slot);
   SLOGI("Booting slot %u: isSlotMarkedSuccessful=%d\n", current_slot, is_successful);
-
   if (is_successful == 0) {
     // The current slot has not booted successfully.
-
-    // TODO: Add the actual verification after we have the A/B OTA package
-    // format in place.
-
-    // TODO: Assert the dm-verity mode. Bootloader should never boot a newly
-    // flashed slot (isSlotMarkedSuccessful == 0) with dm-verity logging mode.
+    char verity_mode[PROPERTY_VALUE_MAX];
+    if (property_get("ro.boot.veritymode", verity_mode, "") == -1) {
+      SLOGE("Failed to get dm-verity mode");
+      return -1;
+    } else if (strcmp(verity_mode, "EIO") == 0) {
+      // We shouldn't see verity in EIO mode if the current slot hasn't booted
+      // successfully before. Therefore, fail the verification when veirtymode=EIO.
+      SLOGE("Found dm-verity in EIO mode, skip verification.");
+      return -1;
+    } else if (strcmp(verity_mode, "enforcing") != 0) {
+      SLOGE("Unexpected dm-verity mode : %s, expecting enforcing.", verity_mode);
+      return -1;
+    } else if (!verify_image(CARE_MAP_FILE)) {
+      SLOGE("Failed to verify all blocks in care map file.\n");
+      return -1;
+    }
 
     int ret = module->markBootSuccessful(module);
     if (ret != 0) {