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[3.10] bpo-42982: Improve the text on suggested number of iterations of PBKDF2 (GH-24276) #30951

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Jan 27, 2022
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[3.10] bpo-42982: Improve the text on suggested number of iterations of PBKDF2 (GH-24276) #30951

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9 changes: 7 additions & 2 deletions Doc/library/hashlib.rst
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Expand Up @@ -249,8 +249,9 @@ include a `salt <https://en.wikipedia.org/wiki/Salt_%28cryptography%29>`_.
a proper source, e.g. :func:`os.urandom`.

The number of *iterations* should be chosen based on the hash algorithm and
computing power. As of 2013, at least 100,000 iterations of SHA-256 are
suggested.
computing power. As of 2022, hundreds of thousands of iterations of SHA-256
are suggested. For rationale as to why and how to choose what is best for
your application, read *Appendix A.2.2* of NIST-SP-800-132_.

*dklen* is the length of the derived key. If *dklen* is ``None`` then the
digest size of the hash algorithm *hash_name* is used, e.g. 64 for SHA-512.
Expand Down Expand Up @@ -731,6 +732,7 @@ Domain Dedication 1.0 Universal:
.. _SHA-3: https://en.wikipedia.org/wiki/NIST_hash_function_competition
.. _ChaCha: https://cr.yp.to/chacha.html
.. _pyblake2: https://pythonhosted.org/pyblake2/
.. _NIST-SP-800-132: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf



Expand All @@ -754,3 +756,6 @@ Domain Dedication 1.0 Universal:

https://www.ietf.org/rfc/rfc8018.txt
PKCS #5: Password-Based Cryptography Specification Version 2.1

https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf
NIST Recommendation for Password-Based Key Derivation.