diff --git a/src/client/http_client.rs b/src/client/http_client.rs
index 1053e45a..46ddf758 100644
--- a/src/client/http_client.rs
+++ b/src/client/http_client.rs
@@ -5,6 +5,8 @@ use hyper::Body;
 use hyper::client::Client;
 use xdg::BaseDirectories;
 use chrono::Utc;
+use std::collections::HashSet;
+use std::sync::{Arc, Mutex};
 
 use http::{Request, Response};
 use http::header::HeaderValue;
@@ -465,10 +467,50 @@ impl H2Client {
         (verify_queue_tx, verify_result_rx)
     }
 
+    pub fn download_chunk_list(
+        &self,
+        path: &str,
+        archive_name: &str,
+        known_chunks: Arc<Mutex<HashSet<[u8;32]>>>,
+    ) -> impl Future<Item=(), Error=Error> {
+
+        let param = json!({ "archive-name": archive_name });
+        let request = Self::request_builder("localhost", "GET", path, Some(param)).unwrap();
+
+        self.send_request(request, None)
+            .and_then(move |response| {
+                response
+                    .map_err(Error::from)
+                    .and_then(move |resp| {
+                        let status = resp.status();
+                        if !status.is_success() {
+                            bail!("download chunk list failed with status {}", status);
+                        }
+
+                        let (_head, body) = resp.into_parts();
+
+                        Ok(body)
+                    })
+                    .and_then(move |mut body| {
+
+                        let mut release_capacity = body.release_capacity().clone();
+
+                        crate::backup::DigestListDecoder::new(body.map_err(Error::from))
+                            .for_each(move |chunk| {
+                                let _ = release_capacity.release_capacity(chunk.len());
+                                println!("GOT DOWNLOAD {}", tools::digest_to_hex(&chunk));
+                                known_chunks.lock().unwrap().insert(chunk);
+                                Ok(())
+                            })
+                       })
+            })
+    }
+
     pub fn upload_stream(
         &self,
         wid: u64,
-        stream: impl Stream<Item=Vec<u8>, Error=Error>,
+        stream: impl Stream<Item=bytes::BytesMut, Error=Error>,
+        known_chunks: Arc<Mutex<HashSet<[u8;32]>>>,
     ) -> impl Future<Item=usize, Error=Error> {
 
         let repeat = std::sync::Arc::new(AtomicUsize::new(0));
@@ -492,18 +534,20 @@ impl H2Client {
 
                 let digest = openssl::sha::sha256(&data);
 
-                let chunk_is_known = false;
+                let mut known_chunks = known_chunks.lock().unwrap();
+                let chunk_is_known = known_chunks.contains(&digest);
 
                 let upload_data;
                 let request;
 
-                println!("upload chunk ({} bytes)", data.len());
-
                 if chunk_is_known {
+                    println!("append existing chunk ({} bytes)", data.len());
                     let param = json!({ "wid": wid, "digest": tools::digest_to_hex(&digest) });
                     request = Self::request_builder("localhost", "PUT", "dynamic_index", Some(param)).unwrap();
                     upload_data = None;
                 } else {
+                    println!("upload new chunk {} ({} bytes)", tools::digest_to_hex(&digest), data.len());
+                    known_chunks.insert(digest);
                     let param = json!({ "wid": wid, "size" : data.len() });
                     request = Self::request_builder("localhost", "POST", "dynamic_chunk", Some(param)).unwrap();
                     upload_data = Some(bytes::Bytes::from(data));