Bisq onion key sign/verify shell script

bisq-sign.sh

#!/bin/sh
FILE_TO_SIGN="$1"
PRIVATE_KEYFILE_PEM=$HOME/.local/share/Bisq/btc_mainnet/tor/hiddenservice/private_key
PUBLIC_KEYFILE_PEM=/tmp/pubkey.pem
PUBLIC_KEYFILE_DER=/tmp/pubkey.der
SIGNATURE_FILE=/tmp/signature

echo "public key in PEM:"
openssl rsa -in "${PRIVATE_KEYFILE_PEM}" -pubout -outform PEM -out "${PUBLIC_KEYFILE_PEM}"
openssl rsa -in "${PRIVATE_KEYFILE_PEM}" -pubout -outform DER -out "${PUBLIC_KEYFILE_DER}"
cat "${PUBLIC_KEYFILE_PEM}"

ONION=$(tail -c +23 "${PUBLIC_KEYFILE_DER}" | shasum -a 1 | head -c 20 | xxd -r -p | base32 | awk '{print tolower($0)}')
echo "onion hostname: ${ONION}"

echo "text to sign:"
cat "${FILE_TO_SIGN}"

echo "digest to sign:"
DIGEST=$(shasum -a 256 ${FILE_TO_SIGN} | awk '{print $1}')
echo "${DIGEST}"

echo "signature:"
openssl dgst -sha256 -sign "${PRIVATE_KEYFILE_PEM}" -keyform PEM "${FILE_TO_SIGN}" > "${SIGNATURE_FILE}"
base64 "${SIGNATURE_FILE}"

echo "verify"
openssl dgst -sha256 -verify "${PUBLIC_KEYFILE_PEM}" -keyform PEM -signature "${SIGNATURE_FILE}" "${FILE_TO_SIGN}"