diff --git a/migrations/Version20260402203207.php b/migrations/Version20260402203207.php
new file mode 100644
index 0000000..e6d135e
--- /dev/null
+++ b/migrations/Version20260402203207.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20260402203207 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return '';
+    }
+
+    public function up(Schema $schema): void
+    {
+        // this up() migration is auto-generated, please modify it to your needs
+        $this->addSql('ALTER TABLE advert ADD hmac VARCHAR(128) NOT NULL');
+        $this->addSql('ALTER TABLE devis ADD hmac VARCHAR(128) NOT NULL');
+        $this->addSql('ALTER TABLE facture ADD hmac VARCHAR(128) NOT NULL');
+    }
+
+    public function down(Schema $schema): void
+    {
+        // this down() migration is auto-generated, please modify it to your needs
+        $this->addSql('ALTER TABLE advert DROP hmac');
+        $this->addSql('ALTER TABLE devis DROP hmac');
+        $this->addSql('ALTER TABLE facture DROP hmac');
+    }
+}
diff --git a/src/Entity/Advert.php b/src/Entity/Advert.php
index 92db721..ca9754b 100644
--- a/src/Entity/Advert.php
+++ b/src/Entity/Advert.php
@@ -23,6 +23,9 @@ class Advert
     #[ORM\JoinColumn(nullable: true)]
     private ?Devis $devis = null;
 
+    #[ORM\Column(length: 128)]
+    private string $hmac;
+
     #[ORM\Column]
     private \DateTimeImmutable $createdAt;
 
@@ -30,11 +33,12 @@ class Advert
     #[ORM\OneToMany(targetEntity: Facture::class, mappedBy: 'advert')]
     private Collection $factures;
 
-    public function __construct(OrderNumber $orderNumber)
+    public function __construct(OrderNumber $orderNumber, string $hmacSecret)
     {
         $this->orderNumber = $orderNumber;
         $this->createdAt = new \DateTimeImmutable();
         $this->factures = new ArrayCollection();
+        $this->hmac = $this->generateHmac($hmacSecret);
     }
 
     public function getId(): ?int
@@ -57,6 +61,11 @@ class Advert
         $this->devis = $devis;
     }
 
+    public function getHmac(): string
+    {
+        return $this->hmac;
+    }
+
     public function getCreatedAt(): \DateTimeImmutable
     {
         return $this->createdAt;
@@ -67,4 +76,20 @@ class Advert
     {
         return $this->factures;
     }
+
+    public function verifyHmac(string $hmacSecret): bool
+    {
+        return hash_equals($this->hmac, $this->generateHmac($hmacSecret));
+    }
+
+    private function generateHmac(string $secret): string
+    {
+        $payload = implode('|', [
+            'advert',
+            $this->orderNumber->getNumOrder(),
+            $this->createdAt->format('Y-m-d\TH:i:s'),
+        ]);
+
+        return hash_hmac('sha256', $payload, $secret);
+    }
 }
diff --git a/src/Entity/Devis.php b/src/Entity/Devis.php
index bc94960..94ddcf3 100644
--- a/src/Entity/Devis.php
+++ b/src/Entity/Devis.php
@@ -19,6 +19,9 @@ class Devis
     #[ORM\JoinColumn(nullable: false)]
     private OrderNumber $orderNumber;
 
+    #[ORM\Column(length: 128)]
+    private string $hmac;
+
     #[ORM\Column]
     private \DateTimeImmutable $createdAt;
 
@@ -26,11 +29,12 @@ class Devis
     #[ORM\OneToMany(targetEntity: Advert::class, mappedBy: 'devis')]
     private Collection $adverts;
 
-    public function __construct(OrderNumber $orderNumber)
+    public function __construct(OrderNumber $orderNumber, string $hmacSecret)
     {
         $this->orderNumber = $orderNumber;
         $this->createdAt = new \DateTimeImmutable();
         $this->adverts = new ArrayCollection();
+        $this->hmac = $this->generateHmac($hmacSecret);
     }
 
     public function getId(): ?int
@@ -43,6 +47,11 @@ class Devis
         return $this->orderNumber;
     }
 
+    public function getHmac(): string
+    {
+        return $this->hmac;
+    }
+
     public function getCreatedAt(): \DateTimeImmutable
     {
         return $this->createdAt;
@@ -53,4 +62,20 @@ class Devis
     {
         return $this->adverts;
     }
+
+    public function verifyHmac(string $hmacSecret): bool
+    {
+        return hash_equals($this->hmac, $this->generateHmac($hmacSecret));
+    }
+
+    private function generateHmac(string $secret): string
+    {
+        $payload = implode('|', [
+            'devis',
+            $this->orderNumber->getNumOrder(),
+            $this->createdAt->format('Y-m-d\TH:i:s'),
+        ]);
+
+        return hash_hmac('sha256', $payload, $secret);
+    }
 }
diff --git a/src/Entity/Facture.php b/src/Entity/Facture.php
index 0ed4a56..5b94885 100644
--- a/src/Entity/Facture.php
+++ b/src/Entity/Facture.php
@@ -27,13 +27,17 @@ class Facture
     #[ORM\Column(type: 'smallint', options: ['default' => 0])]
     private int $splitIndex = 0;
 
+    #[ORM\Column(length: 128)]
+    private string $hmac;
+
     #[ORM\Column]
     private \DateTimeImmutable $createdAt;
 
-    public function __construct(OrderNumber $orderNumber)
+    public function __construct(OrderNumber $orderNumber, string $hmacSecret)
     {
         $this->orderNumber = $orderNumber;
         $this->createdAt = new \DateTimeImmutable();
+        $this->hmac = $this->generateHmac($hmacSecret);
     }
 
     public function getId(): ?int
@@ -77,8 +81,30 @@ class Facture
         return $this->splitIndex > 0 ? $num.'-'.$this->splitIndex : $num;
     }
 
+    public function getHmac(): string
+    {
+        return $this->hmac;
+    }
+
     public function getCreatedAt(): \DateTimeImmutable
     {
         return $this->createdAt;
     }
+
+    public function verifyHmac(string $hmacSecret): bool
+    {
+        return hash_equals($this->hmac, $this->generateHmac($hmacSecret));
+    }
+
+    private function generateHmac(string $secret): string
+    {
+        $payload = implode('|', [
+            'facture',
+            $this->orderNumber->getNumOrder(),
+            (string) $this->splitIndex,
+            $this->createdAt->format('Y-m-d\TH:i:s'),
+        ]);
+
+        return hash_hmac('sha256', $payload, $secret);
+    }
 }
diff --git a/src/Service/AdvertService.php b/src/Service/AdvertService.php
index f3224c2..9a57c7d 100644
--- a/src/Service/AdvertService.php
+++ b/src/Service/AdvertService.php
@@ -5,25 +5,24 @@ namespace App\Service;
 use App\Entity\Advert;
 use App\Entity\Devis;
 use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
 
 class AdvertService
 {
     public function __construct(
         private OrderNumberService $orderNumberService,
         private EntityManagerInterface $em,
+        #[Autowire('%env(APP_SECRET)%')] private string $hmacSecret,
     ) {
     }
 
-    /**
-     * Cree un advert avec un nouveau numero de commande.
-     */
     public function create(?Devis $devis = null): Advert
     {
         $orderNumber = null !== $devis
             ? $devis->getOrderNumber()
             : $this->orderNumberService->generateAndUse();
 
-        $advert = new Advert($orderNumber);
+        $advert = new Advert($orderNumber, $this->hmacSecret);
 
         if (null !== $devis) {
             $advert->setDevis($devis);
@@ -35,9 +34,6 @@ class AdvertService
         return $advert;
     }
 
-    /**
-     * Cree un advert a partir d'un devis existant (meme numero).
-     */
     public function createFromDevis(Devis $devis): Advert
     {
         return $this->create($devis);
diff --git a/src/Service/DevisService.php b/src/Service/DevisService.php
index 820ecf4..3e6f25a 100644
--- a/src/Service/DevisService.php
+++ b/src/Service/DevisService.php
@@ -4,22 +4,21 @@ namespace App\Service;
 
 use App\Entity\Devis;
 use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
 
 class DevisService
 {
     public function __construct(
         private OrderNumberService $orderNumberService,
         private EntityManagerInterface $em,
+        #[Autowire('%env(APP_SECRET)%')] private string $hmacSecret,
     ) {
     }
 
-    /**
-     * Cree un devis avec un nouveau numero de commande.
-     */
     public function create(): Devis
     {
         $orderNumber = $this->orderNumberService->generateAndUse();
-        $devis = new Devis($orderNumber);
+        $devis = new Devis($orderNumber, $this->hmacSecret);
 
         $this->em->persist($devis);
         $this->em->flush();
diff --git a/src/Service/FactureService.php b/src/Service/FactureService.php
index 6dba0b9..f56c68e 100644
--- a/src/Service/FactureService.php
+++ b/src/Service/FactureService.php
@@ -5,18 +5,17 @@ namespace App\Service;
 use App\Entity\Advert;
 use App\Entity\Facture;
 use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
 
 class FactureService
 {
     public function __construct(
         private OrderNumberService $orderNumberService,
         private EntityManagerInterface $em,
+        #[Autowire('%env(APP_SECRET)%')] private string $hmacSecret,
     ) {
     }
 
-    /**
-     * Cree une facture avec un nouveau numero de commande (facture seule).
-     */
     public function create(?Advert $advert = null): Facture
     {
         if (null !== $advert) {
@@ -24,7 +23,7 @@ class FactureService
         }
 
         $orderNumber = $this->orderNumberService->generateAndUse();
-        $facture = new Facture($orderNumber);
+        $facture = new Facture($orderNumber, $this->hmacSecret);
 
         $this->em->persist($facture);
         $this->em->flush();
@@ -32,20 +31,16 @@ class FactureService
         return $facture;
     }
 
-    /**
-     * Cree une facture a partir d'un advert (meme numero + splitIndex si plusieurs).
-     */
     public function createFromAdvert(Advert $advert): Facture
     {
         $existingCount = $advert->getFactures()->count();
 
-        $facture = new Facture($advert->getOrderNumber());
+        $facture = new Facture($advert->getOrderNumber(), $this->hmacSecret);
         $facture->setAdvert($advert);
 
         if ($existingCount > 0) {
             $facture->setSplitIndex($existingCount + 1);
 
-            // La premiere facture existante doit aussi avoir un splitIndex si elle n'en a pas
             $firstFacture = $advert->getFactures()->first();
             if (false !== $firstFacture && 0 === $firstFacture->getSplitIndex()) {
                 $firstFacture->setSplitIndex(1);