diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7c9d9b6..98eaade 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Fixed
 
+- `ValueError` when trying to decrypt empty metadata values ([#766](https://github.com/pdfminer/pdfminer.six/issues/766))
 - Sphinx errors during building of documentation ([#760](https://github.com/pdfminer/pdfminer.six/pull/760))
 - `TypeError` when getting default width of font ([#720](https://github.com/pdfminer/pdfminer.six/issues/720))
 
diff --git a/pdfminer/pdftypes.py b/pdfminer/pdftypes.py
index f4543b9..d7a2f41 100644
--- a/pdfminer/pdftypes.py
+++ b/pdfminer/pdftypes.py
@@ -138,6 +138,8 @@ def resolve_all(x: object, default: object = None) -> Any:
 def decipher_all(decipher: DecipherCallable, objid: int, genno: int, x: object) -> Any:
     """Recursively deciphers the given object."""
     if isinstance(x, bytes):
+        if len(x) == 0:
+            return x
         return decipher(objid, genno, x)
     if isinstance(x, list):
         x = [decipher_all(decipher, objid, genno, v) for v in x]