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+# Algorithm implementations used by the `hashlib` module.
+
+This code comes from the
+[HACL\*](https://github.com/hacl-star/hacl-star/) project.
+
+HACL\* is a cryptographic library that has been formally verified for memory
+safety, functional correctness, and secret independence.
+
+## Updating HACL*
+
+Use the `refresh.sh` script in this directory to pull in a new upstream code
+version.  The upstream git hash used for the most recent code pull is recorded
+in the script.  Modify the script as needed to bring in more if changes are
+needed based on upstream code refactoring.
+
+Never manually edit HACL\* files. Always add transformation shell code to the
+`refresh.sh` script to perform any necessary edits. If there are serious code
+changes needed, work with the upstream repository.
+
+## Local files
+
+1. `./include/python_hacl_namespaces.h`
+1. `./README.md`
+1. `./refresh.sh`
+
+## ACKS
+
+* Jonathan Protzenko aka [@msprotz on Github](https://github.com/msprotz)
+contributed our HACL\* based builtin code.