p->mgf(maskbuffer, db_buffer, db_len, hv_len, p->mgf_parameter);
memxor(seed_buffer, maskbuffer, hv_len);
p->mgf(maskbuffer, seed_buffer, hv_len, db_len, p->mgf_parameter);
memxor(db_buffer, maskbuffer, db_len);
if(memcmp(label_hv, db_buffer, hv_len)){
p->mgf(maskbuffer, db_buffer, db_len, hv_len, p->mgf_parameter);
memxor(seed_buffer, maskbuffer, hv_len);
p->mgf(maskbuffer, seed_buffer, hv_len, db_len, p->mgf_parameter);
memxor(db_buffer, maskbuffer, db_len);
if(memcmp(label_hv, db_buffer, hv_len)){