diff --git a/UnleashedRecomp/user/achievement_data.cpp b/UnleashedRecomp/user/achievement_data.cpp
index 0325ab27..f08d5164 100644
--- a/UnleashedRecomp/user/achievement_data.cpp
+++ b/UnleashedRecomp/user/achievement_data.cpp
@@ -3,10 +3,29 @@
 #include <ui/achievement_overlay.h>
 #include <user/config.h>
 
+#define NUM_RECORDS sizeof(Data.Records) / sizeof(Record)
+
+time_t AchievementData::GetTimestamp(uint16_t id)
+{
+    for (int i = 0; i < NUM_RECORDS; i++)
+    {
+        if (!Data.Records[i].ID)
+            break;
+
+        if (Data.Records[i].ID == id)
+            return Data.Records[i].Timestamp;
+    }
+
+    return 0;
+}
+
 bool AchievementData::IsUnlocked(uint16_t id)
 {
-    for (int i = 0; i < sizeof(Data.Records) / sizeof(Record); i++)
+    for (int i = 0; i < NUM_RECORDS; i++)
     {
+        if (!Data.Records[i].ID)
+            break;
+
         if (Data.Records[i].ID == id)
             return true;
     }
@@ -19,7 +38,7 @@ void AchievementData::Unlock(uint16_t id)
     if (IsUnlocked(id))
         return;
 
-    for (int i = 0; i < sizeof(Data.Records) / sizeof(Record); i++)
+    for (int i = 0; i < NUM_RECORDS; i++)
     {
         if (Data.Records[i].ID == 0)
         {
@@ -33,15 +52,39 @@ void AchievementData::Unlock(uint16_t id)
         AchievementOverlay::Open(id);
 }
 
-time_t AchievementData::GetTimestamp(uint16_t id)
+uint32_t AchievementData::CalculateChecksum()
 {
-    for (int i = 0; i < sizeof(Data.Records) / sizeof(Record); i++)
+    auto result = 0;
+
+    for (int i = 0; i < NUM_RECORDS; i++)
     {
-        if (Data.Records[i].ID == id)
-            return Data.Records[i].Timestamp;
+        auto& record = Data.Records[i];
+
+        for (size_t j = 0; j < sizeof(Record); j++)
+            result ^= ((uint8_t*)(&record))[j];
     }
 
-    return 0;
+    return result;
+}
+
+bool AchievementData::VerifySignature()
+{
+    char sig[4] = ACH_SIGNATURE;
+
+    return Data.Signature[0] == sig[0] &&
+           Data.Signature[1] == sig[1] &&
+           Data.Signature[2] == sig[2] &&
+           Data.Signature[3] == sig[3];
+}
+
+bool AchievementData::VerifyVersion()
+{
+    return Data.Version == Version ACH_VERSION;
+}
+
+bool AchievementData::VerifyChecksum()
+{
+    return Data.Checksum == CalculateChecksum();
 }
 
 void AchievementData::Load()
@@ -55,11 +98,48 @@ void AchievementData::Load()
 
     if (!file)
     {
-        printf("[*] Failed to parse achievement data.\n");
+        printf("[*] ERROR: failed to read achievement data.\n");
         return;
     }
 
+    file.read((char*)&Data.Signature, sizeof(Data.Signature));
+
+    if (!VerifySignature())
+    {
+        printf("[*] ERROR: invalid achievement data signature.\n");
+
+        char sig[4] = ACH_SIGNATURE;
+
+        Data.Signature[0] = sig[0];
+        Data.Signature[1] = sig[1];
+        Data.Signature[2] = sig[2];
+        Data.Signature[3] = sig[3];
+
+        file.close();
+
+        return;
+    }
+
+    file.read((char*)&Data.Version, sizeof(Data.Version));
+
+    if (!VerifyVersion())
+    {
+        printf("[*] ERROR: unsupported achievement data version.\n");
+        Data.Version = ACH_VERSION;
+        file.close();
+        return;
+    }
+
+    file.seekg(0);
     file.read((char*)&Data, sizeof(Data));
+
+    // TODO: display error message to user before wiping data?
+    if (!VerifyChecksum())
+    {
+        printf("[*] ERROR: achievement data checksum mismatch.\n");
+        memset(&Data.Records, 0, sizeof(Data.Records));
+    }
+
     file.close();
 }
 
@@ -69,10 +149,12 @@ void AchievementData::Save()
 
     if (!file)
     {
-        printf("[*] Failed to write achievement data.\n");
+        printf("[*] ERROR: failed to write achievement data.\n");
         return;
     }
 
+    Data.Checksum = CalculateChecksum();
+
     file.write((const char*)&Data, sizeof(Data));
     file.close();
 }
diff --git a/UnleashedRecomp/user/achievement_data.h b/UnleashedRecomp/user/achievement_data.h
index df06e7bd..942c9841 100644
--- a/UnleashedRecomp/user/achievement_data.h
+++ b/UnleashedRecomp/user/achievement_data.h
@@ -1,10 +1,9 @@
 #pragma once
 
-#include <cstdint>
 #include <user/paths.h>
 
-#define ACH_SIGNATURE 'ACH '
-#define ACH_VERSION 0x01000000
+#define ACH_SIGNATURE { 'A', 'C', 'H', ' ' }
+#define ACH_VERSION   { 1, 0, 0 }
 
 class AchievementData
 {
@@ -18,12 +17,28 @@ public:
     };
 #pragma pack(pop)
 
+    struct Version
+    {
+        uint8_t Major;
+        uint8_t Minor;
+        uint8_t Revision;
+        uint8_t Reserved;
+
+        bool operator==(const Version& other) const
+        {
+            return Major == other.Major &&
+                   Minor == other.Minor &&
+                   Revision == other.Revision;
+        }
+    };
+
     class Data
     {
     public:
-        uint32_t Signature{};
-        uint32_t Version{};
-        uint32_t Reserved[2];
+        char Signature[4];
+        Version Version{};
+        uint32_t Checksum;
+        uint32_t Reserved;
         Record Records[50];
     };
 
@@ -34,9 +49,13 @@ public:
         return GetSavePath() / "ACH-DATA";
     }
 
+    static time_t GetTimestamp(uint16_t id);
     static bool IsUnlocked(uint16_t id);
     static void Unlock(uint16_t id);
-    static time_t GetTimestamp(uint16_t id);
+    static uint32_t CalculateChecksum();
+    static bool VerifySignature();
+    static bool VerifyVersion();
+    static bool VerifyChecksum();
     static void Load();
     static void Save();
 };