diff --git a/lib/tasks/blobs.rake b/lib/tasks/blobs.rake
new file mode 100644
index 000000000..eedda7f9c
--- /dev/null
+++ b/lib/tasks/blobs.rake
@@ -0,0 +1,37 @@
+namespace :blobs do
+  desc <<~EOD
+    given a file blob_ids.json with contains { blob_ids: [...] },
+    download and reattached champ piece_justificative_file to create new blob
+    and delete the old one, and thus, invalides old signed_ids.
+
+    bin/rails 'blobs:renew_signed_ids[blob_ids.json]'
+  EOD
+  task :renew_signed_ids, [:file_path] => :environment do |_t, args|
+    blob_ids = JSON.parse(File.read(args[:file_path]))['blob_ids']
+    blobs = ActiveStorage::Blob.find(blob_ids)
+
+    blobs.each do |blob|
+      blob.open do |file|
+        blob.attachments.each do |attachment|
+          if [attachment.record_type, attachment.name] != ['Champ', 'piece_justificative_file']
+            raise "not a piece justificative #{attachment.id}"
+          end
+          champ = attachment.record
+          champ_updated_at = champ.updated_at
+          dossier = champ.dossier
+          dossier_updated_at = dossier.updated_at
+
+          file.rewind
+
+          # badly, it updates champ and dossier updated_at attributes
+          champ.piece_justificative_file.attach(io: file, filename: blob.filename, content_type: blob.content_type)
+          # it destroys the blob as well
+          attachment.destroy
+
+          champ.update_column(:updated_at, champ_updated_at)
+          dossier.update_column(:updated_at, dossier_updated_at)
+        end
+      end
+    end
+  end
+end