diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..27ace47
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+venv
+logs
+results
+*.pyc
+__pycache__
\ No newline at end of file
diff --git a/albs-oval-errata-diff.py b/albs-oval-errata-diff.py
new file mode 100644
index 0000000..8c59f90
--- /dev/null
+++ b/albs-oval-errata-diff.py
@@ -0,0 +1,4 @@
+from albs_oval_erratta_diff.start import start
+
+
+start()
diff --git a/albs_oval_erratta_diff/__init__.py b/albs_oval_erratta_diff/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/albs_oval_erratta_diff/comparer.py b/albs_oval_erratta_diff/comparer.py
new file mode 100644
index 0000000..3d96971
--- /dev/null
+++ b/albs_oval_erratta_diff/comparer.py
@@ -0,0 +1,254 @@
+import bz2
+import datetime
+import re
+import requests
+from typing import Tuple, List, Dict, Any
+import xml.etree.ElementTree as ET
+import logging
+import json
+
+from .config import DOWNLOAD_DIR, NOT_BEFORE, RELEASES, SA_EXCLUDE, PACKAGES_EXCLUDE
+from .sa import SecurityAdvisory
+from .package import Package
+
+
+def download_oval(url: str) -> str:
+    """
+    download_oval downloads, decompreses oval file
+    and returns filepath of saved file
+    """
+    r = requests.get(url, stream=True, timeout=30)
+    decompressor = bz2.BZ2Decompressor()
+    fname = url.split('/')[-1].replace('.bz2', '')
+    fpath = DOWNLOAD_DIR / fname
+    with open(fpath, 'wb') as fd:
+        for chunk in r.iter_content(chunk_size=128):
+            fd.write(decompressor.decompress(chunk))
+    return fpath
+
+
+def download_errata(url: str, release_version: int) -> str:
+    """
+    downloads errata_full.json file end returns file path
+    """
+    response = requests.get(url, stream=True, timeout=30)
+    fname = f'alma-{release_version}.json'
+    fpath = DOWNLOAD_DIR / fname
+    with open(fpath, 'wb') as errata_file:
+        for chunk in response.iter_content(chunk_size=128):
+            errata_file.write(chunk)
+    return fpath
+
+
+def parse_oval(fpath: str) -> Dict[str, SecurityAdvisory]:
+    """
+    converting oval xml file to dict
+    """
+
+    def extract_package(title: str) -> Package:
+        r = r'(.*) is earlier than \d+:(.+?(?=-))'
+        res = re.search(r, title)
+        name = res.group(1)
+        version = res.group(2)
+        return Package(name=name, version=version)
+
+    def extract_id(title: str) -> str:
+        r = r'[RH|AL]SA-(\d{4}:\d+)(.*)'
+        res = re.search(r, title)
+        return res.group(1)
+
+    tree = ET.parse(fpath)
+    root = tree.getroot()
+    ns = {
+        'n': 'http://oval.mitre.org/XMLSchema/oval-definitions-5',
+
+    }
+    res = {}
+    for definition in root.findall('n:definitions/', ns):
+        title = definition.find('n:metadata/n:title', ns).text
+        issued = definition.find(
+            'n:metadata/n:advisory/n:issued', ns).attrib['date']
+        issued_dt = datetime.datetime.strptime(issued, "%Y-%m-%d")
+
+        # we are only  interesed in Security advisories after RHEL 8.3
+        if ('RHSA' not in title and 'ALSA' not in title) or issued_dt < NOT_BEFORE:
+            continue
+        sa_id = extract_id(title)
+        packages = [extract_package(i.attrib['comment']) for i in definition.findall(".//n:criterion", ns)
+                    if 'is earlier than' in i.attrib['comment']]
+        res[sa_id] = SecurityAdvisory(
+            title=title, id=sa_id, packages=packages)
+    return res
+
+
+def parse_errata(fpath: str) -> Dict[str, SecurityAdvisory]:
+    """
+    parses alma errata file and converts it to dict of SA instances
+    """
+    with open(fpath, 'r', encoding='utf-8') as file_to_load:
+        erratas = json.load(file_to_load)
+    res = {}
+    for errata in erratas['data']:
+        title = errata['title']
+        sa_id = errata['id'].split('-')[-1]
+        packages = []
+        for package in errata['packages']:
+            full_name = f"{package['name']}-{package['version']}"
+            if full_name not in packages:
+                packages.append(full_name)
+        packages.sort()
+        res[sa_id] = SecurityAdvisory(
+            title=title, id=sa_id, packages=packages)
+    return res
+
+
+def compare(rhel_oval: Dict[str, SecurityAdvisory],
+            alma_oval: Dict[str, SecurityAdvisory],
+            alma_errata: Dict[str, SecurityAdvisory]) -> Tuple[dict, list]:
+    """
+    compares rhel oval with alma oval and alma errata
+    """
+    diff = []
+    report = {
+        # total amount of security advisories
+        'total_sa_count': 0,
+        # amount of SA that match with rhel
+        'good_sa_count': 0,
+        # total amount of differencies
+        'diff_count': 0,
+        # list of SA excluded from diff check
+        'excluded_sa': [],
+        # list of packages excluded from  diff check
+        'excluded_pkg': [],
+        # amount of oval SA that dont exists in oval file
+        'oval_missing_sa_count': 0,
+        # amount of oval SA that have missing packages
+        'oval_missing_pkg_sa_count': 0,
+        # list of missing oval SA
+        'oval_missing_sa': [],
+        # list of oval SA that have missing packages
+        'oval_missing_pkg_sa': [],
+        # amount of SA that dont exists in errata file
+        'errata_missing_sa_count': 0,
+        # amount of errata SA that have missing packages
+        'errata_missing_pkg_sa_count': 0,
+        # list of SA that are missing in errata file
+        'errata_missing_sa': [],
+        # list of errata SA with missing packages
+        'errata_missing_pkg_sa': [],
+        # total amount of unique missing packages across all alma SA
+        'missing_packages_unique_count': 0,
+        # list of unique packages that missing across all alma SA
+        'missing_packages_unique': []
+    }
+
+    for rhel_sa_id, rhel_sa in rhel_oval.items():
+        report['total_sa_count'] += 1
+        sa_name = f'ALSA-{rhel_sa_id}'
+
+        # filtering out SA
+        if sa_name in SA_EXCLUDE:
+            report['excluded_sa'].append(sa_name)
+            continue
+
+        # filtefing out packages
+        packages_to_check: List[Package] = []
+        for p in rhel_sa.packages:
+            if any(p.name == i for i in PACKAGES_EXCLUDE):
+                if str(p) not in report['excluded_pkg']:
+                    report['excluded_pkg'].append(str(p))
+            else:
+                packages_to_check.append(p)
+
+        # check oval
+        try:
+            alma_oval_sa = alma_oval[rhel_sa_id]
+        except KeyError:
+            report['diff_count'] += 1
+            diff.append({'sa_name': sa_name, 'diff': 'SA is missing in oval'})
+            report['oval_missing_sa'].append(sa_name)
+            report['oval_missing_sa_count'] += 1
+        else:
+            # check if some packages are missing from oval SA
+            alma_oval_packages = alma_oval_sa.packages
+            alma_oval_missing_packages = [str(r) for r in packages_to_check
+                                          if r not in alma_oval_packages]
+            if alma_oval_missing_packages:
+                report['diff_count'] += 1
+                diff.append({'sa_name': sa_name,
+                            'diff': f"missing packages in oval SA: {','.join(alma_oval_missing_packages)}"})
+                report['oval_missing_pkg_sa'].append(sa_name)
+                report['oval_missing_pkg_sa_count'] += 1
+                for mp in alma_oval_missing_packages:
+                    if mp not in report['missing_packages_unique']:
+                        report['missing_packages_unique'].append(mp)
+                        report['missing_packages_unique_count'] += 1
+
+        # check errata
+        try:
+            alma_errata_sa = alma_errata[rhel_sa_id]
+        except KeyError:
+            report['errata_missing_sa'].append(sa_name)
+            report['errata_missing_sa_count'] += 1
+            report['diff_count'] += 1
+            diff.append(
+                {'sa_name': sa_name, 'diff': 'SA is missing in errata'})
+            continue
+        # check if some packages are missing from errata SA
+        alma_errata_packages = alma_errata_sa.packages
+        alma_errata_missing_packages = [
+            str(r) for r in packages_to_check if r not in alma_errata_packages]
+        if alma_errata_missing_packages:
+            report['diff_count'] += 1
+            diff.append({'sa_name': sa_name,
+                         'diff': f"missing packages in errata SA: {','.join(alma_errata_missing_packages)}"})
+            report['errata_missing_pkg_sa'].append(sa_name)
+            report['errata_missing_pkg_sa_count'] += 1
+            for mp in alma_errata_missing_packages:
+                if mp not in report['missing_packages_unique']:
+                    report['missing_packages_unique'].append(mp)
+                    report['missing_packages_unique_count'] += 1
+        else:
+            # if we here, all checks were passed
+            report['good_sa_count'] += 1
+
+    for item in report.values():
+        if isinstance(item, list):
+            item.sort()
+    return report, diff
+
+
+# starting point
+def comparer_run() -> Dict[str, Any]:
+    result = {}
+    for release, urls in RELEASES.items():
+        logging.info('Processing release %i', release)
+
+        logging.info('downloading rhel oval')
+        rhel_file = download_oval(urls['rhel_oval_url'])
+        logging.info('parsing rhel oval')
+        rhel_oval_dict = parse_oval(rhel_file)
+
+        logging.info('downloading alma oval')
+        alma_oval_file = download_oval(urls['alma_oval_url'])
+        logging.info('parsing alma oval')
+        alma_oval_dict = parse_oval(alma_oval_file)
+
+        logging.info('downloading alma errata')
+        alma_errata_file = download_errata(urls['alma_errata_url'], release)
+        logging.info('parsing alma errata')
+        alma_errata_dict = parse_errata(alma_errata_file)
+
+        logging.info('comparing rhel and alma')
+        report_release, diff_release = compare(
+            rhel_oval_dict, alma_oval_dict, alma_errata_dict)
+        result[release] = {'report': report_release,
+                           'diff': diff_release,
+                           'rhel_oval_url': urls['rhel_oval_url'],
+                           'alma_oval_url': urls['alma_oval_url'],
+                           'alma_errata_url': urls['alma_errata_url']}
+
+    result['report_generated'] = datetime.datetime.now().timestamp() * 1000
+    result['sa_not_before'] = NOT_BEFORE.timestamp() * 1000
+
+    return result
diff --git a/albs_oval_erratta_diff/config.py b/albs_oval_erratta_diff/config.py
new file mode 100644
index 0000000..73bedcd
--- /dev/null
+++ b/albs_oval_erratta_diff/config.py
@@ -0,0 +1,21 @@
+from pathlib import Path
+import datetime
+
+RELEASES = {
+    8: {'rhel_oval_url': 'https://www.redhat.com/security/data/oval/v2/RHEL8/rhel-8.oval.xml.bz2',
+        'alma_oval_url': 'https://repo.almalinux.org/security/oval/org.almalinux.alsa-8.xml.bz2',
+        'alma_errata_url': "https://errata.almalinux.org/8/errata.full.json", },
+    9: {'rhel_oval_url': 'https://www.redhat.com/security/data/oval/v2/RHEL9/rhel-9.oval.xml.bz2',
+        'alma_oval_url': 'https://repo.almalinux.org/security/oval/org.almalinux.alsa-9.xml.bz2',
+        'alma_errata_url': "https://errata.almalinux.org/9/errata.full.json", }
+}
+LOG_FILE = Path('logs/albs-oval-errata-diff.log')
+DIFF_FILE = Path('results/diff.json')
+DOWNLOAD_DIR = Path('/tmp')
+# not checking anything before RHEL-9.0 release
+NOT_BEFORE = datetime.datetime(2022, 5, 18)
+UPDATE_INTERVAL_MINUTES = 30
+SERVER_PORT = 3001
+SERVER_IP = "127.0.0.1"
+SA_EXCLUDE = []
+PACKAGES_EXCLUDE = ["dotnet-sdk-3.1-source-built-artifacts"]
diff --git a/albs_oval_erratta_diff/package.py b/albs_oval_erratta_diff/package.py
new file mode 100644
index 0000000..03ca6f5
--- /dev/null
+++ b/albs_oval_erratta_diff/package.py
@@ -0,0 +1,14 @@
+from dataclasses import dataclass
+from typing import List
+
+
+@dataclass
+class Package:
+    """
+    Package represents RPM package exstracted from RHEL OVAL
+    """
+    name: str
+    version: str
+
+    def __str__(self):
+        return f"{self.name}-{self.version}"
diff --git a/albs_oval_erratta_diff/sa.py b/albs_oval_erratta_diff/sa.py
new file mode 100644
index 0000000..7e4dbfb
--- /dev/null
+++ b/albs_oval_erratta_diff/sa.py
@@ -0,0 +1,15 @@
+from dataclasses import dataclass
+from typing import List
+
+from .package import Package
+
+
+@dataclass
+class SecurityAdvisory:
+    """
+    SecurityAdvisory represents Security advisory deffition extracted
+    from oval or errata
+    """
+    title: str
+    id: str
+    packages: List[Package]
diff --git a/albs_oval_erratta_diff/start.py b/albs_oval_erratta_diff/start.py
new file mode 100644
index 0000000..bab92b9
--- /dev/null
+++ b/albs_oval_erratta_diff/start.py
@@ -0,0 +1,98 @@
+"""
+service compares rhel oval with alma ovals and errata ovals
+results available via API Call
+"""
+from aiohttp import web
+import copy
+import logging
+import threading
+from time import sleep
+import json
+
+from .config import LOG_FILE, DIFF_FILE, UPDATE_INTERVAL_MINUTES, SERVER_IP, SERVER_PORT
+from .comparer import comparer_run
+
+
+# This dict holds all current differentes
+diffs = {}
+diffs_lock = threading.Lock()
+
+
+async def web_handler(request):
+    data = {}
+    try:
+        diffs_lock.acquire()
+        data = copy.deepcopy(diffs)
+        diffs_lock.release()
+    except Exception as e:
+        logging.critical("Unhandled exeption %s", e, exc_info=True)
+    return web.json_response(data=data)
+
+
+def webserver_run():
+    app = web.Application()
+    app.add_routes([web.get('/', web_handler)])
+    web.run_app(app=app, host=SERVER_IP, port=SERVER_PORT)
+
+
+def diff_checker():
+    while True:
+        logging.info("Start comparing")
+        # generating new diff
+        try:
+            result = comparer_run()
+        except Exception as e:
+            logging.critical("Unhandled exeption %s", e, exc_info=True)
+        else:
+            logging.info("Finished comparing, updating diff dict")
+            diffs_lock.acquire()
+            global diffs
+            diffs = result
+            diffs_lock.release()
+        # dumping
+        logging.info("Saving results to disk")
+        try:
+            with open(DIFF_FILE, 'w', encoding='utf-8') as flw:
+                json.dump(result, flw, indent=4)
+        except Exception as e:
+            logging.critical("Unhandled exeption %s", e, exc_info=True)
+        logging.info("Done")
+
+        logging.info("Finished comparing, go to sleep for %d minutes",
+                     UPDATE_INTERVAL_MINUTES)
+        sleep(UPDATE_INTERVAL_MINUTES * 60)
+
+
+def start():
+    # making sure that directory exists
+    for p in [LOG_FILE, DIFF_FILE]:
+        if not p.parent.exists():
+            p.parent.mkdir()
+
+    logging.basicConfig(level=logging.INFO,
+                        format='%(asctime)s %(levelname)s %(funcName)s %(message)s',
+                        handlers=[logging.FileHandler(LOG_FILE, mode='a'),
+                                  logging.StreamHandler()])
+
+    logging.info("Trying to load diff file from disk")
+    try:
+        with open(DIFF_FILE, 'r', encoding='utf-8') as flr:
+            loaded_data = json.load(flr)
+        diffs_lock.acquire()
+        diffs = loaded_data
+        diffs_lock.release()
+    except Exception as e:
+        logging.warning('cant load data from disk %s', e)
+    else:
+        logging.info('diff file was loaded')
+
+    logging.info("Starting diff_checker in background")
+    thread = threading.Thread(target=diff_checker)
+    thread.daemon = True
+    thread.start()
+    logging.info("Starting webserver")
+    webserver_run()
+
+
+if __name__ == "__main__":
+    start()