On 29/04/2021 15:04, Joe Eremita wrote: > datasig_len = i2d_X509_REQ_INFO( req->req_info, NULL ); You can achieve this by instead doing: datasig_len = i2d_re_X509_REQ_tbs(req, NULL); See: https://www.openssl.org/docs/man1.1.1/man3/i2d_re_X509_REQ_tbs.html Matt