diff --git a/confsync/tests/test_core.py b/confsync/tests/test_core.py
new file mode 100644
index 0000000..574008a
--- /dev/null
+++ b/confsync/tests/test_core.py
@@ -0,0 +1,280 @@
+"""Tests for core utilities and encryption."""
+
+import pytest
+import tempfile
+import os
+from pathlib import Path
+
+from confsync.utils.file_utils import (
+    calculate_file_hash,
+    read_file_safe,
+    write_file_safe,
+    find_files_matching,
+    get_file_size,
+)
+from confsync.utils.path_utils import (
+    expand_path,
+    normalize_path,
+    get_home_directory,
+    get_xdg_config_dir,
+    is_subpath,
+)
+from confsync.utils.encryption import EncryptionManager, EncryptedData
+
+
+class TestFileUtils:
+    """Tests for file utilities."""
+
+    def test_calculate_hash(self):
+        """Test hash calculation."""
+        content1 = "test content"
+        content2 = "test content"
+
+        hash1 = calculate_file_hash(content1)
+        hash2 = calculate_file_hash(content2)
+
+        assert hash1 == hash2
+        assert len(hash1) == 64
+
+    def test_calculate_hash_different(self):
+        """Test hash calculation for different content."""
+        hash1 = calculate_file_hash("content 1")
+        hash2 = calculate_file_hash("content 2")
+
+        assert hash1 != hash2
+
+    def test_read_file_safe_success(self):
+        """Test reading file successfully."""
+        with tempfile.NamedTemporaryFile(mode='w', delete=False) as f:
+            f.write("test content")
+            temp_path = f.name
+
+        try:
+            content = read_file_safe(temp_path)
+            assert content == "test content"
+        finally:
+            os.unlink(temp_path)
+
+    def test_read_file_safe_nonexistent(self):
+        """Test reading nonexistent file."""
+        content = read_file_safe("/nonexistent/path/file.txt")
+        assert content is None
+
+    def test_write_file_safe_success(self):
+        """Test writing file successfully."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            path = os.path.join(tmpdir, "test.txt")
+            success = write_file_safe("test content", path)
+
+            assert success
+            assert os.path.exists(path)
+            with open(path, 'r') as f:
+                assert f.read() == "test content"
+
+    def test_find_files_matching(self):
+        """Test finding files by pattern."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            Path(os.path.join(tmpdir, "file1.json")).touch()
+            Path(os.path.join(tmpdir, "file2.json")).touch()
+            Path(os.path.join(tmpdir, "file3.yaml")).touch()
+
+            json_files = find_files_matching(tmpdir, ["*.json"])
+
+            assert len(json_files) == 2
+            assert all(f.endswith('.json') for f in json_files)
+
+    def test_get_file_size(self):
+        """Test getting file size."""
+        with tempfile.NamedTemporaryFile(mode='w', delete=False) as f:
+            f.write("1234567890")
+            temp_path = f.name
+
+        try:
+            size = get_file_size(temp_path)
+            assert size == 10
+        finally:
+            os.unlink(temp_path)
+
+
+class TestPathUtils:
+    """Tests for path utilities."""
+
+    def test_expand_path_tilde(self):
+        """Test expanding home directory."""
+        expanded = expand_path("~/config")
+        assert expanded.startswith("/")
+        assert "config" in expanded
+
+    def test_expand_path_env(self):
+        """Test expanding environment variables."""
+        os.environ["TEST_VAR"] = "test_value"
+        expanded = expand_path("$TEST_VAR/path")
+        assert "test_value" in expanded
+
+    def test_normalize_path(self):
+        """Test normalizing paths."""
+        path = normalize_path("~/./config")
+        assert path.startswith("/")
+
+    def test_get_home_directory(self):
+        """Test getting home directory."""
+        home = get_home_directory()
+        assert home.startswith("/")
+        assert os.path.exists(home)
+
+    def test_get_xdg_config_dir(self):
+        """Test getting XDG config directory."""
+        xdg = get_xdg_config_dir()
+        assert xdg.startswith("/")
+
+    def test_is_subpath(self):
+        """Test subpath detection."""
+        assert is_subpath("/home/user/config", "/home/user")
+        assert is_subpath("/home/user/.config/file", "/home/user/.config")
+
+
+class TestEncryption:
+    """Tests for encryption utilities."""
+
+    def test_encrypt_decrypt(self):
+        """Test encryption and decryption."""
+        enc_manager = EncryptionManager(passphrase="test_passphrase")
+
+        original = "sensitive data"
+
+        encrypted = enc_manager.encrypt(original)
+        assert isinstance(encrypted, EncryptedData)
+        assert len(encrypted.salt) == 16
+
+        decrypted = enc_manager.decrypt(encrypted, passphrase="test_passphrase")
+        assert decrypted == original
+
+    def test_encrypt_manifest_roundtrip(self):
+        """Test manifest encryption roundtrip."""
+        enc_manager = EncryptionManager(passphrase="test_passphrase")
+
+        manifest_data = '{"version": "1.0.0", "entries": []}'
+
+        encrypted = enc_manager.encrypt_manifest(manifest_data)
+        assert isinstance(encrypted, str)
+
+        decrypted = enc_manager.decrypt_manifest(encrypted)
+        assert decrypted == manifest_data
+
+    def test_encrypt_file(self):
+        """Test file encryption."""
+        enc_manager = EncryptionManager(passphrase="test_passphrase")
+
+        with tempfile.NamedTemporaryFile(mode='w', delete=False) as f:
+            f.write("sensitive content")
+            input_path = f.name
+
+        try:
+            output_path = enc_manager.encrypt_file(input_path)
+
+            assert os.path.exists(output_path)
+            assert output_path != input_path
+
+            with open(output_path, 'rb') as f:
+                content = f.read()
+                assert len(content) > 16
+
+            os.unlink(output_path)
+        finally:
+            os.unlink(input_path)
+
+    def test_verify_key(self):
+        """Test key verification."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            key_path = os.path.join(tmpdir, "test.key")
+
+            enc_manager = EncryptionManager(key_file=key_path, passphrase="test_passphrase")
+
+            enc_manager.generate_key_file(key_path, "test_passphrase")
+
+            assert os.path.exists(key_path)
+            assert enc_manager.verify_key(key_path, "test_passphrase") is True
+            assert enc_manager.verify_key(key_path, "wrong_passphrase") is False
+
+
+class TestSyncMetadata:
+    """Tests for sync metadata model."""
+
+    def test_sync_metadata_serialization(self):
+        """Test SyncMetadata serialization."""
+        from confsync.models.config_models import SyncMetadata, SyncOperation
+
+        metadata = SyncMetadata(
+            operation=SyncOperation.PUSH,
+            source="/local",
+            destination="/remote",
+        )
+
+        data = metadata.to_dict()
+
+        assert data["operation"] == "push"
+        assert data["source"] == "/local"
+        assert data["destination"] == "/remote"
+
+    def test_sync_metadata_from_dict(self):
+        """Test SyncMetadata deserialization."""
+        from confsync.models.config_models import SyncMetadata, SyncOperation
+
+        data = {
+            "operation": "pull",
+            "source": "/remote",
+            "destination": "/local",
+            "timestamp": "2024-01-01T00:00:00",
+            "committed_files": [],
+            "conflicts": [],
+            "merged_files": [],
+            "status": "success",
+            "error_message": None,
+        }
+
+        metadata = SyncMetadata.from_dict(data)
+
+        assert metadata.operation == SyncOperation.PULL
+        assert metadata.status == "success"
+
+
+class TestHistoryEntry:
+    """Tests for history entry model."""
+
+    def test_history_entry_serialization(self):
+        """Test HistoryEntry serialization."""
+        from confsync.models.config_models import HistoryEntry
+
+        entry = HistoryEntry(
+            operation="sync",
+            files_changed=[".vimrc", ".bashrc"],
+            commit_message="Update configs",
+        )
+
+        data = entry.to_dict()
+
+        assert data["operation"] == "sync"
+        assert len(data["files_changed"]) == 2
+
+    def test_history_entry_from_dict(self):
+        """Test HistoryEntry deserialization."""
+        from confsync.models.config_models import HistoryEntry
+
+        data = {
+            "id": "test-id",
+            "timestamp": "2024-01-01T00:00:00",
+            "operation": "rollback",
+            "files_changed": [".vimrc"],
+            "commit_message": "Rollback to previous",
+            "diff": None,
+            "tags": [],
+        }
+
+        entry = HistoryEntry.from_dict(data)
+
+        assert entry.id == "test-id"
+        assert entry.operation == "rollback"
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])