diff --git a/contrib/extract-secp256k1.sh b/contrib/extract-secp256k1.sh
new file mode 100755
--- /dev/null
+++ b/contrib/extract-secp256k1.sh
@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+
+export LC_ALL=C
+
+pushd "$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 && pwd)"
+REPO_DIR=$(git rev-parse --show-toplevel)
+popd
+
+git clone "file://${REPO_DIR}" workdir -b master
+
+pushd workdir
+FILTER_BRANCH_SQUELCH_WARNING=1 git filter-branch \
+    --index-filter 'git ls-files \
+                        | grep -v ^src/secp256k1 \
+                        | xargs git rm -q --cached;
+                    git ls-files -s \
+                        | sed "s%src/secp256k1/%%" \
+                        | git update-index --index-info;
+                    git rm -rq --cached --ignore-unmatch src/secp256k1' \
+    --prune-empty -- --all
+popd
+
+# filter-branch is full of gotcha and can leave the repo is a strange state,
+# so we make a fresh new one.
+git clone "file://$(pwd)/workdir" secp256k1
+rm -rf workdir
+
+pushd secp256k1
+git remote add github https://github.com/Bitcoin-ABC/secp256k1.git
+git pull github master --rebase
+git gc --prune=now
+