Remove a detailed discussion of content-based short circuiting, off topic for library docs.
diff --git a/Doc/library/hmac.rst b/Doc/library/hmac.rst
index 809636e..38f1687 100644
--- a/Doc/library/hmac.rst
+++ b/Doc/library/hmac.rst
@@ -70,22 +70,13 @@
.. function:: compare_digest(a, b)
- Return ``a == b``. This function uses an approach designed to prevent timing
- analysis by avoiding content based short circuiting behaviour, making it
- appropriate for cryptography. *a* and *b* must both be of the same type:
- either :class:`str` (ASCII only, as e.g. returned by
+ Return ``a == b``. This function uses an approach designed to prevent
+ timing analysis by avoiding content-based short circuiting behaviour,
+ making it appropriate for cryptography. *a* and *b* must both be of the
+ same type: either :class:`str` (ASCII only, as e.g. returned by
:meth:`HMAC.hexdigest`), or any type that supports the buffer protocol
(e.g. :class:`bytes`).
- Using a short circuiting comparison (that is, one that terminates as soon as
- it finds any difference between the values) to check digests for correctness
- can be problematic, as it introduces a potential vulnerability when an
- attacker can control both the message to be checked *and* the purported
- signature value. By keeping the plaintext consistent and supplying different
- signature values, an attacker may be able to use timing variations to search
- the signature space for the expected value in O(n) time rather than the
- desired O(2**n).
-
.. note::
If *a* and *b* are of different lengths, or if an error occurs,