Add more information about the reference impl

README.md

@@ -5,6 +5,7 @@ part of the [NIST submission](https://classic.mceliece.org/nist.html) by
 Bernstein et al.
 
 This version is based on the round-2 submission `mceliece-20190331`.
+See [`deps/mceliece`](deps/mceliece).
 
 ## Installation
 

deps/mceliece/README.md

@@ -1,4 +1,35 @@
-The contents of this directory are generated automatically by the `prepare`
-script. The `kem` directory contains the
-[reference implementation](https://classic.mceliece.org/nist.html) provided by
-Bernstein et al.
+# Reference implementation of Classic McEliece
+
+The `kem` directory contains the reference implementation of the Classic
+McEliece KEM that was provided by Bernstein et al. as part of the
+[Classic McEliece NIST submission](https://classic.mceliece.org/nist.html).
+
+- Source: Round-2 submission package
+- Revision: `mceliece-20190331`
+- File: [`mceliece-20190331.tar.gz`](https://classic.mceliece.org/nist/mceliece-20190331.tar.gz)
+  - `e298f8bb1380a74d1f5990cb6e921f45` (md5)
+  - `ec08d18f430601c6661a4d0cfe5f5592fb8d6edb` (sha1)
+  - `3fa54e9139bb62338445047cb25ab73b0e1e576288f729d20ce4db8c2236f678` (sha256)
+
+## Automatically applied patches
+
+The `extract-kem-from-nist-submission` script was used to generate the contents
+of the `kem` directory as well as the header file `mceliece.h` and the file
+`binding.gyp`.
+
+The contents of the `kem` directory correspond to the contents of the
+`Reference_Implementation/kem` directory that is part of the submission package.
+However, the `extract-kem-from-nist-submission` script applies the following
+patches.
+
+- The reference implementation uses libkeccak to implement SHAKE256. However,
+  because Node.js uses OpenSSL by default, references to libkeccak header files
+  are replaced with references to [`mceliece_externals.h`](mceliece_externals.h)
+  that defines a compatible interface. The implementation of the interface
+  uses OpenSSL.
+- The reference implementation uses a random number generator that is based on
+  AES256-CTR. Instead, we patch the implementation to use the AES implementation
+  and the random number generator provided by OpenSSL via
+  [`mceliece_externals.h`](mceliece_externals.h).
+- Files that are not required for providing bindings for the reference
+  implementation are removed (e.g., `KATNUM`).