diff --git a/docs/algorithm.md b/docs/algorithm.md
index 315a8d7..58ef78a 100644
--- a/docs/algorithm.md
+++ b/docs/algorithm.md
@@ -14,16 +14,16 @@ Assuming all sources are reliable.
 
 We list all combinations mutually exclusive and collectively exhaustive.
 
-| ID  | Remote Files | Local files | Local delete rename history | Extra                                                      | Decision                                                                                          |
-| --- | ------------ | ----------- | --------------------------- | ---------------------------------------------------------- | ------------------------------------------------------------------------------------------------- |
-| 1   | exist        | exist       | ignore                      | mtime_remote > mtime_local                                 | download remote file, create local folder if not exists, clear local history if exists            |
-| 2   | exist        | exist       | ignore                      | mtime_remote < mtime_local                                 | upload local file, create remote folder if not exists, clear local history if exists              |
-| 3   | exist        | exist       | ignore                      | mtime_remote === mtime_local && size_remote === size_local | clear local history if exists (the file was synced and no changes after last sync)                |
-| 4   | exist        | exist       | ignore                      | mtime_remote === mtime_local && size_remote !== size_local | upload local file, clear local history if exists (we always prefer local to remote)               |
-| 5   | exist        | exist       | ignore                      | If local is a folder. mtime_local === undefined            | clear local history if exists. TODO: what if a folder and a previous file share the same name?    |
-| 6   | exist        | not exist   | exist                       | mtime_remote >= delete_time_local                          | download remote file, create folder if not exists                                                 |
-| 7   | exist        | not exist   | exist                       | mtime_remote < delete_time_local                           | delete remote file, clear local history                                                           |
-| 8   | exist        | not exist   | not exist                   |                                                            | download remote file, create folder if not exists                                                 |
-| 9   | not exist    | exist       | ignore                      | If local is a single file.                                 | upload local file, create remote folder if not exists, clear local history if exists              |
-| 10  | not exist    | exist       | ignore                      | If local is a folder.                                      | upload local files recursively, create remote folder if not exists, clear local history if exists |
-| 11  | not exist    | not exist   | ignore                      |                                                            | clear local history if exists                                                                     |
+| ID   | Remote Files | Local files | Local delete rename history | Extra                                                        | Decision                                                     |
+| ---- | ------------ | ----------- | --------------------------- | ------------------------------------------------------------ | ------------------------------------------------------------ |
+| 1    | exist        | exist       | ignore                      | mtime_remote > mtime_local                                   | download remote file, create local folder if not exists, clear local history if exists |
+| 2    | exist        | exist       | ignore                      | mtime_remote < mtime_local                                   | upload local file, create remote folder if not exists, clear local history if exists |
+| 3    | exist        | exist       | ignore                      | mtime_remote === mtime_local && password === "" && size_remote === size_local | clear local history if exists (the file was synced and no changes after last sync) |
+| 4    | exist        | exist       | ignore                      | mtime_remote === mtime_local && password === "" && size_remote !== size_local | upload local file, clear local history if exists (we always prefer local to remote) |
+| 5    | exist        | exist       | ignore                      | mtime_remote === mtime_local && password !== ""              | clear local history if exists (in encryption mode, file sizes are unequal. we can only rely on mtime(s)) |
+| 6    | exist        | exist       | ignore                      | If local is a folder. mtime_local === undefined              | clear local history if exists. TODO: what if a folder and a previous file share the same name? |
+| 7    | exist        | not exist   | exist                       | mtime_remote >= delete_time_local                            | download remote file, create folder if not exists            |
+| 8    | exist        | not exist   | exist                       | mtime_remote < delete_time_local                             | delete remote file, clear local history                      |
+| 9    | exist        | not exist   | not exist                   |                                                              | download remote file, create folder if not exists            |
+| 10   | not exist    | exist       | ignore                      | local may be folder or file                                  | upload local files recursively, create remote folder if not exists, clear local history if exists |
+| 11   | not exist    | not exist   | ignore                      |                                                              | clear local history if exists                                |
diff --git a/src/sync.ts b/src/sync.ts
index 7db9219..d2ef4f5 100644
--- a/src/sync.ts
+++ b/src/sync.ts
@@ -190,7 +190,8 @@ const ensembleMixedStates = async (
 
 const getOperation = (
   origRecord: FileOrFolderMixedState,
-  inplace: boolean = false
+  inplace: boolean = false,
+  password: string = ""
 ) => {
   let r = origRecord;
   if (!inplace) {
@@ -238,6 +239,7 @@ const getOperation = (
     r.mtime_remote !== undefined &&
     r.mtime_local !== undefined &&
     r.mtime_remote === r.mtime_local &&
+    password === "" &&
     r.size_local === r.size_remote
   ) {
     r.decision = "skip";
@@ -248,17 +250,31 @@ const getOperation = (
     r.mtime_remote !== undefined &&
     r.mtime_local !== undefined &&
     r.mtime_remote === r.mtime_local &&
+    password === "" &&
     r.size_local !== r.size_remote
   ) {
     r.decision = "upload_clearhist";
     r.decision_branch = 4;
+  } else if (
+    r.exist_remote &&
+    r.exist_local &&
+    r.mtime_remote !== undefined &&
+    r.mtime_local !== undefined &&
+    r.mtime_remote === r.mtime_local &&
+    password !== ""
+  ) {
+    // if we have encryption,
+    // the size is always unequal
+    // only mtime(s) are reliable
+    r.decision = "skip";
+    r.decision_branch = 5;
   } else if (r.exist_remote && r.exist_local && r.mtime_local === undefined) {
     // this must be a folder!
     if (!r.key.endsWith("/")) {
       throw Error(`${r.key} is not a folder but lacks local mtime`);
     }
     r.decision = "skip";
-    r.decision_branch = 5;
+    r.decision_branch = 6;
   } else if (
     r.exist_remote &&
     !r.exist_local &&
@@ -268,7 +284,7 @@ const getOperation = (
     r.mtime_remote >= r.delete_time_local
   ) {
     r.decision = "download_clearhist";
-    r.decision_branch = 6;
+    r.decision_branch = 7;
   } else if (
     r.exist_remote &&
     !r.exist_local &&
@@ -278,7 +294,7 @@ const getOperation = (
     r.mtime_remote < r.delete_time_local
   ) {
     r.decision = "delremote_clearhist";
-    r.decision_branch = 7;
+    r.decision_branch = 8;
   } else if (
     r.exist_remote &&
     !r.exist_local &&
@@ -287,10 +303,10 @@ const getOperation = (
     r.delete_time_local == undefined
   ) {
     r.decision = "download";
-    r.decision_branch = 8;
+    r.decision_branch = 9;
   } else if (!r.exist_remote && r.exist_local && r.mtime_remote === undefined) {
     r.decision = "upload_clearhist";
-    r.decision_branch = 9;
+    r.decision_branch = 10;
   } else if (
     !r.exist_remote &&
     !r.exist_local &&
@@ -298,7 +314,7 @@ const getOperation = (
     r.mtime_local === undefined
   ) {
     r.decision = "clearhist";
-    r.decision_branch = 10;
+    r.decision_branch = 11;
   }
 
   return r;