diff --git a/include/jwt/jwt.h b/include/jwt/jwt.h
index dfd7933..643cd53 100644
--- a/include/jwt/jwt.h
+++ b/include/jwt/jwt.h
@@ -6,11 +6,11 @@ extern "C"
 {
 #endif
 
-    auto create_token(const char* user_id, const char* secret) noexcept -> char*;
+    char* create_token(const char* user_id, const char* secret);
 
-    auto get_payload(const char* token) noexcept -> char*;
+    char* get_payload(const char* token);
 
-    auto verify_token(const char* token, const char* secret) noexcept -> int;
+    int verify_token(const char* token, const char* secret);
 
 #ifdef __cplusplus
 }
diff --git a/include/server/auth.h b/include/server/auth.h
new file mode 100644
index 0000000..675cee5
--- /dev/null
+++ b/include/server/auth.h
@@ -0,0 +1,6 @@
+#ifndef SERVER_AUTH_H
+#define SERVER_AUTH_H
+
+// Your code here
+
+#endif // SERVER_AUTH_H
\ No newline at end of file
diff --git a/src/db/auth.cpp b/src/db/auth.cpp
new file mode 100644
index 0000000..5d678c5
--- /dev/null
+++ b/src/db/auth.cpp
@@ -0,0 +1,79 @@
+#include "auth.h"
+
+#include "hash/hash.hpp"
+
+#include <print>
+
+#include <leveldb/db.h>
+
+using leveldb_ptr = leveldb::DB*;
+
+auto user_db    = leveldb_ptr{nullptr};
+auto iter_round = 10000;
+
+extern "C"
+{
+    auto open_user_db() -> int
+    {
+        auto opts = leveldb::Options{};
+
+        opts.create_if_missing = true;
+
+        auto status = leveldb::DB::Open(opts, "db/user", &user_db);
+
+        if (!status.ok()) {
+            std::println(stderr, "Failed to open user database: {}", status.ToString());
+            return 0;
+        }
+        return 1;
+    }
+
+    auto close_user_db() -> void
+    {
+        delete user_db;
+    }
+
+    auto check_user_exists(const char* user_id, int* result) -> int
+    {
+        auto value  = std::string{};
+        auto status = user_db->Get(leveldb::ReadOptions{}, user_id, &value);
+        if (status.ok()) {
+            *result = 1;
+        } else if (status.IsNotFound()) {
+            *result = 0;
+        } else {
+            std::println(stderr, "Failed to check user existence: {}", status.ToString());
+            return 0;
+        }
+        return 1;
+    }
+
+    auto set_user_password(const char* user_id, const char* password) -> int
+    {
+        auto status = user_db->Put(leveldb::WriteOptions{}, user_id, generate_hash(password, iter_round));
+        if (!status.ok()) {
+            std::println(stderr, "Failed to set user password: {}", status.ToString());
+            return 0;
+        }
+        return 1;
+    }
+
+    auto login(const char* user_id, const char* password, int* result) -> int
+    {
+        auto value  = std::string{};
+        auto status = user_db->Get(leveldb::ReadOptions{}, user_id, &value);
+        if (!status.ok()) {
+            std::println(stderr, "Failed to login: {}", status.ToString());
+            return 0;
+        }
+        *result = validate_password(password, value.data());
+        return 1;
+    }
+
+    auto logout(const char* user_id) -> int
+    {
+        leveldb::WriteOptions write_options;
+        leveldb::Status status = user_db->Delete(write_options, user_id);
+        return status.ok();
+    }
+}
\ No newline at end of file
diff --git a/src/jwt/jwt.cpp b/src/jwt/jwt.cpp
index 43485f7..d83e6f9 100644
--- a/src/jwt/jwt.cpp
+++ b/src/jwt/jwt.cpp
@@ -8,7 +8,7 @@ using namespace std::literals::chrono_literals;
 
 extern "C"
 {
-    auto create_token(const char* user_id, const char* secret) noexcept -> char*
+    auto create_token(const char* user_id, const char* secret) -> char*
     {
         auto token = jwt::create()
                          .set_type("JWS")
@@ -21,14 +21,14 @@ extern "C"
         return strdup(token.c_str());
     }
 
-    auto get_payload(const char* token) noexcept -> char*
+    auto get_payload(const char* token) -> char*
     {
         auto decoded_token = jwt::decode(token);
         auto payload       = decoded_token.get_payload_claim("user_id").as_string();
         return strdup(payload.c_str());
     }
 
-    auto verify_token(const char* token, const char* secret) noexcept -> int
+    auto verify_token(const char* token, const char* secret) -> int
     {
         try {
             auto decoded_token = jwt::decode(token);