diff --git a/client/cli/bam.py b/client/cli/bam.py
index 2ddb486..e99b2ff 100755
--- a/client/cli/bam.py
+++ b/client/cli/bam.py
@@ -220,7 +220,7 @@ class bam_session:
         paths_remove = {}
         paths_modified = {}
 
-        from bam_utils.system import sha1_from_file
+        from bam_utils.system import uuid_from_file
 
         session_rootdir = os.path.abspath(session_rootdir)
 
@@ -237,7 +237,7 @@ class bam_session:
         for f_rel, sha1 in paths_uuid.items():
             f_abs = os.path.join(session_rootdir, f_rel)
             if os.path.exists(f_abs):
-                sha1_modified = sha1_from_file(f_abs)
+                sha1_modified = uuid_from_file(f_abs)
                 if sha1_modified != sha1:
                     paths_modified[f_rel] = f_abs
                 if paths_uuid_update is not None:
@@ -272,7 +272,7 @@ class bam_session:
                 paths_add[f_rel] = f_abs
 
                 if paths_uuid_update is not None:
-                    paths_uuid_update[f_rel] = sha1_from_file(f_abs)
+                    paths_uuid_update[f_rel] = uuid_from_file(f_abs)
 
         return paths_add, paths_remove, paths_modified
 
diff --git a/modules/bam_utils/system.py b/modules/bam_utils/system.py
index 3174a72..7bb1902 100644
--- a/modules/bam_utils/system.py
+++ b/modules/bam_utils/system.py
@@ -45,13 +45,27 @@ else:
         return msg
 
 
-def sha1_from_file(fn, block_size=1 << 20):
+def uuid_from_file(fn, block_size=1 << 20):
+    """
+    Returns an arbitrary sized unique ASCII string based on the file contents.
+    (exact hashing method may change).
+    """
     with open(fn, 'rb') as f:
+        # first get the size
+        import os
+        f.seek(0, os.SEEK_END)
+        size = f.tell()
+        f.seek(0, os.SEEK_SET)
+        del os
+        # done!
+
         import hashlib
-        sha1 = hashlib.new('sha1')
+        sha1 = hashlib.new('sha512')
         while True:
             data = f.read(block_size)
             if not data:
                 break
             sha1.update(data)
-        return sha1.hexdigest()
+        # skip the '0x'
+        return hex(size)[2:] + sha1.hexdigest()
+
diff --git a/modules/blendfile_pack.py b/modules/blendfile_pack.py
index a70c281..2541839 100755
--- a/modules/blendfile_pack.py
+++ b/modules/blendfile_pack.py
@@ -270,23 +270,23 @@ def pack(
         del relbase
 
     if paths_uuid is not None:
-        from bam_utils.system import sha1_from_file
+        from bam_utils.system import uuid_from_file
 
         for src, dst in path_copy_files:
-            paths_uuid[os.path.relpath(dst, base_dir_dst).decode('utf-8')] = sha1_from_file(src)
+            paths_uuid[os.path.relpath(dst, base_dir_dst).decode('utf-8')] = uuid_from_file(src)
         # XXX, better way to store temp target
         blendfile_dst_tmp = temp_remap_cb(blendfile_src, base_dir_src)
-        paths_uuid[os.path.basename(blendfile_src).decode('utf-8')] = sha1_from_file(blendfile_dst_tmp)
+        paths_uuid[os.path.basename(blendfile_src).decode('utf-8')] = uuid_from_file(blendfile_dst_tmp)
 
         # blend libs
         for dst in path_temp_files:
             k = os.path.relpath(dst[:-len(TEMP_SUFFIX)], base_dir_dst_temp).decode('utf-8')
             if k not in paths_uuid:
-                paths_uuid[k] = sha1_from_file(dst)
+                paths_uuid[k] = uuid_from_file(dst)
             del k
 
         del blendfile_dst_tmp
-        del sha1_from_file
+        del uuid_from_file
 
     # --------------------
     # Handle File Copy/Zip
diff --git a/webservice/bam/application/__init__.py b/webservice/bam/application/__init__.py
index 2100627..72a7e58 100644
--- a/webservice/bam/application/__init__.py
+++ b/webservice/bam/application/__init__.py
@@ -375,9 +375,9 @@ class FileAPI(Resource):
                 return
         else:
             # non blend-file
-            from bam_utils.system import sha1_from_file
-            paths_uuid[os.path.basename(filepath)] = sha1_from_file(filepath)
-            del sha1_from_file
+            from bam_utils.system import uuid_from_file
+            paths_uuid[os.path.basename(filepath)] = uuid_from_file(filepath)
+            del uuid_from_file
 
             import zipfile
             with zipfile.ZipFile(filepath_zip, 'w', zipfile.ZIP_DEFLATED) as zip_handle: