private void checkSign() throws Exception {
    final ContentInfo all = new ContentInfo();
    all.decode(new Asn1BerDecodeBuffer(getSignatureBinaryFile()));

    final SignedData cms = (SignedData) all.content;
    final Asn1BerEncodeBuffer encBuf = new Asn1BerEncodeBuffer();

    cms.certificates.elements[0].encode(encBuf);
    final CertificateFactory cf = CertificateFactory.getInstance("X.509");
    final X509Certificate cert = (X509Certificate) cf.generateCertificate(encBuf.getInputStream());

    byte[] text = getFileContent(doc_filename, false);

    CMS.CMSVerify2(cms, cert, text);
    System.exit(0);
}

public static void CMSVerify2(final SignedData cms, Certificate cert, byte[] data) throws Exception {
    int i;
    if (cms.version.value != 1) {
        throw new Exception("Incorrect version");
    }
    if (!new OID(CMStools.STR_CMS_OID_DATA).eq(cms.encapContentInfo.eContentType.value)) {
        throw new Exception("Nested not supported");
    }
    byte[] text = null;
    if (data != null) {
        text = data;
    } else if (cms.encapContentInfo.eContent != null) {
        text = cms.encapContentInfo.eContent.value;
    }
    if (text == null) {
        throw new Exception("No content");
    }
    OID digestOid = null;
    DigestAlgorithmIdentifier a = new DigestAlgorithmIdentifier(new OID(CMStools.DIGEST_OID).value);
    for (i = 0; i < cms.digestAlgorithms.elements.length; i++) {
        if (cms.digestAlgorithms.elements[i].algorithm.equals(a.algorithm)) {
            digestOid = new OID(cms.digestAlgorithms.elements[i].algorithm.value);
            break;
        }
    }
    if (digestOid == null) {
        throw new Exception("Unknown digest");
    }
    int pos = -1;
    for (i = 0; i < cms.certificates.elements.length; i++) {
        final Asn1BerEncodeBuffer encBuf = new Asn1BerEncodeBuffer();
        cms.certificates.elements[i].encode(encBuf);
        final byte[] in = encBuf.getMsgCopy();
        if (Arrays.equals(in, cert.getEncoded())) {
            System.out.println("Certificate: " + ((X509Certificate) cert).getSubjectDN());
            pos = i;
            break;
        }
    }
    if (pos == -1) {
        throw new Exception("Not signed on certificate.");
    }

    final SignerInfo info = cms.signerInfos.elements[pos];
    if (info.version.value != 1) {
        throw new Exception("Incorrect version");
    }
    if (!digestOid.equals(new OID(info.digestAlgorithm.algorithm.value))) {
        throw new Exception("Not signed on certificate.");
    }
    final byte[] sign = info.signature.value;

    // check
    final Signature signature = Signature.getInstance(JCP.GOST_EL_SIGN_NAME);
    signature.initVerify(cert);
    signature.update(text);
    final boolean checkResult = signature.verify(sign);
    if (checkResult) {
        CMStools.logger.info("Valid signature");
    } else {
        CMStools.logger.info("INVALID signature");
    }
    //return text;
}