For timestamping a file with OpenSSL and curl, run the following commands
(setting the $UTS_SERVER_URL, $FILE and $FILE_TIMESTAMP variables):
openssl ts -query -data "$FILE" -out "ts_req.ts";
curl "$UTS_SERVER_URL" \
-H "Content-Type: application/timestamp-query" \
-f -g --data-binary "@ts_req.ts" -o "$FILE_TIMESTAMP"
For verifying the timestamp with OpenSSL, download the CA and the signer cert, and run the following command:
openssl ts -verify -in "$FILE_TIMESTAMP" \
-data "$FILE" -CAfile ca.pem -untrusted tsa_cert.pem