diff --git a/src/frontend/apps/impress/src/features/docs/doc-collaboration/hook/useDocumentEncryption.tsx b/src/frontend/apps/impress/src/features/docs/doc-collaboration/hook/useDocumentEncryption.tsx
index 5ff76dad..bbf05f6a 100644
--- a/src/frontend/apps/impress/src/features/docs/doc-collaboration/hook/useDocumentEncryption.tsx
+++ b/src/frontend/apps/impress/src/features/docs/doc-collaboration/hook/useDocumentEncryption.tsx
@@ -1,7 +1,11 @@
 import { useEffect, useState } from 'react';
 
 import { decryptSymmetricKey } from '@/docs/doc-collaboration/encryption';
-import assert from 'assert';
+
+export type DocumentEncryptionError =
+  | 'missing_symmetric_key'
+  | 'decryption_failed'
+  | null;
 
 export function useDocumentEncryption(
   encryptionLoading: boolean,
@@ -17,11 +21,13 @@ export function useDocumentEncryption(
   documentEncryptionSettings: {
     documentSymmetricKey: CryptoKey;
   } | null;
+  documentEncryptionError: DocumentEncryptionError;
 } {
   const [loading, setLoading] = useState(true);
   const [settings, setSettings] = useState<{
     documentSymmetricKey: CryptoKey;
   } | null>(null);
+  const [error, setError] = useState<DocumentEncryptionError>(null);
 
   useEffect(() => {
     let cancelled = false;
@@ -35,24 +41,27 @@ export function useDocumentEncryption(
       } else if (encryptionLoading || isDocumentEncrypted === undefined) {
         setLoading(true);
         setSettings(null);
+        setError(null);
         return;
       } else if (isDocumentEncrypted === false) {
         setLoading(false);
         setSettings(null);
+        setError(null);
         return;
       }
 
-      // TODO:
-      // TODO: if encrypted but there is no encrypted symmetric key for this user, we should display an error
-      // TODO: (maybe reuse the catch handler below?)
-      // TODO:
-      assert(
-        userEncryptedSymmetricKey,
-        'document encrypted symmetric key must exist',
-      );
+      if (!userEncryptedSymmetricKey) {
+        if (!cancelled) {
+          setError('missing_symmetric_key');
+          setSettings(null);
+          setLoading(false);
+        }
+        return;
+      }
 
       try {
         setLoading(true);
+        setError(null);
 
         const userEncryptedSymmetricKeyArrayBuffer = Buffer.from(
           userEncryptedSymmetricKey,
@@ -70,18 +79,14 @@ export function useDocumentEncryption(
       } catch (err) {
         console.error(err);
 
-        //
-        // TODO: this should display a global error since if encryption needed it should able
-        // to retrieve information (except if onboarding needed, but still...)
-        //
-        // maybe this should be a return value so the parent knows where to set the CTA
-        //
-
         if (!cancelled) {
+          setError('decryption_failed');
           setSettings(null);
         }
       } finally {
-        setLoading(false);
+        if (!cancelled) {
+          setLoading(false);
+        }
       }
     }
 
@@ -95,5 +100,6 @@ export function useDocumentEncryption(
   return {
     documentEncryptionLoading: loading,
     documentEncryptionSettings: settings,
+    documentEncryptionError: error,
   };
 }
diff --git a/src/frontend/apps/impress/src/features/docs/doc-collaboration/hook/useEncryption.tsx b/src/frontend/apps/impress/src/features/docs/doc-collaboration/hook/useEncryption.tsx
index 8c3b45a0..359addc8 100644
--- a/src/frontend/apps/impress/src/features/docs/doc-collaboration/hook/useEncryption.tsx
+++ b/src/frontend/apps/impress/src/features/docs/doc-collaboration/hook/useEncryption.tsx
@@ -2,6 +2,11 @@ import { useEffect, useState } from 'react';
 
 import { getEncryptionDB } from '../encryptionDB';
 
+export type EncryptionError =
+  | 'missing_private_key'
+  | 'missing_public_key'
+  | null;
+
 export function useEncryption(userId?: string): {
   encryptionLoading: boolean;
   encryptionSettings: {
@@ -9,6 +14,7 @@ export function useEncryption(userId?: string): {
     userPrivateKey: CryptoKey;
     userPublicKey: CryptoKey;
   } | null;
+  encryptionError: EncryptionError;
 } {
   const [loading, setLoading] = useState(true);
   const [settings, setSettings] = useState<{
@@ -16,6 +22,7 @@ export function useEncryption(userId?: string): {
     userPrivateKey: CryptoKey;
     userPublicKey: CryptoKey;
   } | null>(null);
+  const [error, setError] = useState<EncryptionError>(null);
 
   const enableEncryption: boolean = true; // TODO: this could be toggled for instances not needing encryption to save some requests
 
@@ -27,15 +34,18 @@ export function useEncryption(userId?: string): {
       if (!userId) {
         setLoading(true);
         setSettings(null);
+        setError(null);
         return;
       } else if (enableEncryption === false) {
         setLoading(false);
         setSettings(null);
+        setError(null);
         return;
       }
 
       try {
         setLoading(true);
+        setError(null);
 
         // We must first retrieve user keys locally
         const encryptionDatabase = await getEncryptionDB();
@@ -46,7 +56,11 @@ export function useEncryption(userId?: string): {
         );
 
         if (!userPrivateKey) {
-          throw new Error('user has no local private key (needs onboarding)');
+          if (!cancelled) {
+            setError('missing_private_key');
+            setSettings(null);
+          }
+          return;
         }
 
         const userPublicKey = await encryptionDatabase.get(
@@ -55,7 +69,11 @@ export function useEncryption(userId?: string): {
         );
 
         if (!userPublicKey) {
-          throw new Error('user is missing his public key');
+          if (!cancelled) {
+            setError('missing_public_key');
+            setSettings(null);
+          }
+          return;
         }
 
         if (!cancelled) {
@@ -68,18 +86,13 @@ export function useEncryption(userId?: string): {
       } catch (err) {
         console.error(err);
 
-        //
-        // TODO: this should display a global error since if encryption needed it should able
-        // to retrieve information (except if onboarding needed, but still...)
-        //
-        // maybe this should be a return value so the parent knows where to set the CTA
-        //
-
         if (!cancelled) {
           setSettings(null);
         }
       } finally {
-        setLoading(false);
+        if (!cancelled) {
+          setLoading(false);
+        }
       }
     }
 
@@ -90,5 +103,9 @@ export function useEncryption(userId?: string): {
     };
   }, [userId, enableEncryption]);
 
-  return { encryptionLoading: loading, encryptionSettings: settings };
+  return {
+    encryptionLoading: loading,
+    encryptionSettings: settings,
+    encryptionError: error,
+  };
 }
diff --git a/src/frontend/apps/impress/src/features/docs/doc-collaboration/index.ts b/src/frontend/apps/impress/src/features/docs/doc-collaboration/index.ts
index ce92d015..b1b8f460 100644
--- a/src/frontend/apps/impress/src/features/docs/doc-collaboration/index.ts
+++ b/src/frontend/apps/impress/src/features/docs/doc-collaboration/index.ts
@@ -8,7 +8,13 @@ export {
   encryptSymmetricKey,
 } from './encryption';
 export { getEncryptionDB } from './encryptionDB';
-export { useDocumentEncryption } from './hook/useDocumentEncryption';
-export { useEncryption } from './hook/useEncryption';
+export {
+  useDocumentEncryption,
+  type DocumentEncryptionError,
+} from './hook/useDocumentEncryption';
+export {
+  useEncryption,
+  type EncryptionError,
+} from './hook/useEncryption';
 export { useKeyFingerprint } from './hook/useKeyFingerprint';
 export { usePublicKeyRegistry } from './hook/usePublicKeyRegistry';
diff --git a/src/frontend/apps/impress/src/pages/docs/[id]/index.tsx b/src/frontend/apps/impress/src/pages/docs/[id]/index.tsx
index 6ae4daeb..1e2c6569 100644
--- a/src/frontend/apps/impress/src/pages/docs/[id]/index.tsx
+++ b/src/frontend/apps/impress/src/pages/docs/[id]/index.tsx
@@ -5,7 +5,9 @@ import { useRouter } from 'next/router';
 import { useEffect, useState } from 'react';
 import { useTranslation } from 'react-i18next';
 
-import { Box, Icon, Loading, TextErrors } from '@/components';
+import { Button } from '@gouvfr-lasuite/cunningham-react';
+
+import { Box, Icon, Loading, StyledLink, Text, TextErrors } from '@/components';
 import { DEFAULT_QUERY_RETRY } from '@/core';
 import { DocEditor } from '@/docs/doc-editor';
 import {
@@ -93,14 +95,18 @@ const DocPage = ({ id }: DocProps) => {
 
   const { authenticated, user } = useAuth();
   const [doc, setDoc] = useState<Doc>();
-  const { encryptionLoading, encryptionSettings } = useEncryption(user?.id);
-  const { documentEncryptionLoading, documentEncryptionSettings } =
-    useDocumentEncryption(
-      encryptionLoading,
-      encryptionSettings,
-      doc?.is_encrypted,
-      doc?.encrypted_document_symmetric_key_for_user,
-    );
+  const { encryptionLoading, encryptionSettings, encryptionError } =
+    useEncryption(user?.id);
+  const {
+    documentEncryptionLoading,
+    documentEncryptionSettings,
+    documentEncryptionError,
+  } = useDocumentEncryption(
+    encryptionLoading,
+    encryptionSettings,
+    doc?.is_encrypted,
+    doc?.encrypted_document_symmetric_key_for_user,
+  );
   const { setCurrentDoc } = useDocStore();
   const { addTask } = useBroadcastStore();
   const queryClient = useQueryClient();
@@ -245,6 +251,98 @@ const DocPage = ({ id }: DocProps) => {
     return <Loading />;
   }
 
+  if (doc.is_encrypted && (encryptionError || documentEncryptionError)) {
+    return (
+      <Box $align="center" $margin="auto" $gap="md" $padding="2rem">
+        <Icon iconName="lock" $size="3rem" $theme="warning" />
+        <Text as="h2" $textAlign="center" $margin="0">
+          {t('Encryption keys unavailable')}
+        </Text>
+        <Box $maxWidth="500px" $gap="sm">
+          <Text $variation="secondary" $textAlign="center">
+            {t(
+              'This is an encrypted document, but your current device does not have the required encryption keys to decrypt it.',
+            )}
+          </Text>
+
+          {(encryptionError === 'missing_private_key' ||
+            encryptionError === 'missing_public_key') && (
+            <Text $variation="secondary" $textAlign="center">
+              {t(
+                'This usually happens when you switch to a new device or browser without restoring your encryption backup.',
+              )}
+            </Text>
+          )}
+
+          {documentEncryptionError === 'missing_symmetric_key' && (
+            <Text $variation="secondary" $textAlign="center">
+              {t(
+                'You do not have access to this encrypted document. Ask the document owner to share it with you again.',
+              )}
+            </Text>
+          )}
+
+          {documentEncryptionError === 'decryption_failed' && (
+            <Text $variation="secondary" $textAlign="center">
+              {t(
+                'Your encryption keys could not decrypt this document. This may happen if your keys were recreated. Ask the document owner to share it with you again.',
+              )}
+            </Text>
+          )}
+        </Box>
+
+        {(encryptionError === 'missing_private_key' ||
+          encryptionError === 'missing_public_key') && (
+          <Box $gap="xs" $maxWidth="500px">
+            <Box
+              $padding="sm"
+              $background="#f0f7ff"
+              $border="1px solid #c5ddf5"
+              $radius="4px"
+              $gap="xs"
+            >
+              <Text $weight="600" $size="sm">
+                {t('Restore from backup (recommended)')}
+              </Text>
+              <Text $size="sm" $variation="secondary">
+                {t(
+                  'If you have previously exported your encryption backup, you can restore it in your account settings to regain access to all your encrypted documents.',
+                )}
+              </Text>
+            </Box>
+            <Box
+              $padding="sm"
+              $background="#fff8f0"
+              $border="1px solid #f5dfc5"
+              $radius="4px"
+              $gap="xs"
+            >
+              <Text $weight="600" $size="sm">
+                {t('Recreate encryption keys (not recommended)')}
+              </Text>
+              <Text $size="sm" $variation="secondary">
+                {t(
+                  'Creating new encryption keys means you will lose access to all previously encrypted documents. Document owners will need to share them with you again.',
+                )}
+              </Text>
+            </Box>
+          </Box>
+        )}
+
+        <StyledLink href="/">
+          <Button
+            color="neutral"
+            icon={
+              <Icon iconName="home" $withThemeInherited />
+            }
+          >
+            {t('Back to home')}
+          </Button>
+        </StyledLink>
+      </Box>
+    );
+  }
+
   return (
     <>
       <Head>