.. note::
- While this function reduces the likelihood of leaking the contents of the
- expected digest via a timing attack, it still may leak some timing
- information when the input values differ in lengths as well as in error
- cases like unsupported types or non ASCII strings. When the inputs have
- different length the timing depends solely on the length of ``b``. It is
- assumed that the expected length of the digest is not a secret, as it is
- typically published as part of a file format, network protocol or API
- definition.
+ If *a* and *b* are of different lengths, or if an error occurs,
+ a timing attack may be able to reveal information about the types
+ and lengths of *a* and *b*, but not their values.
+
.. versionadded:: 3.3