private byte[] noPrefixSign(final byte[] data)
      throws GeneralSecurityException { // https://tools.ietf.org/html/rfc8017#section-8.1.1.
    int modBits = publicKey.getModulus().bitLength();

    byte[] em = emsaPssEncode(data, modBits - 1);
    return rsasp1(em);
  }
RsaSsaPss (i.e. RSA Signature Schemes with Appendix (SSA) with PSS encoding) signing with JCE.
java_src/src/main/java/com/google/crypto/tink/subtle/RsaSsaPssSignJce.java