Sign CAdES using BouncyCastle using JAVA

Question

According to several posts I've found out it's now possible to perform CAdES using BouncyCastle but there is hardly any documentation on the topic.

For starters I want to perform CAdES-BES without any optional signed attributes on a file with a file based certificate.

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In response to dander:

I have something that might be helpful, you have your SignerInformation, you need to extend it, first you need to create an attribute from the timestamp, I'll assume you already have a TimeStampResponse as tspResp

TimeStampToken token = tsresp.getTimeStampToken();

Attribute timeStamp = new Attribute(PKCSObjectIdentifiers.id_aa_signatureTimeStampToken, new DERSet(ASN1Object.fromByteArray(token.getEncoded())));

Then you need to extend your SignerInformation

AttributeTable unsigned = signerInformation.getUnsignedAttributes();
Hashtable<ASN1ObjectIdentifier, Attribute> unsignedAttrHash = null;
if (unsigned == null) {
    unsignedAttrHash = new Hashtable<ASN1ObjectIdentifier, Attribute>();
} else {
    unsignedAttrHash = signerInformation.getUnsignedAttributes().toHashtable();
}

unsignedAttrHash.put(PKCSObjectIdentifiers.id_aa_signatureTimeStampToken, signatureTimeStamp);

SignerInformation newsi = SignerInformation.replaceUnsignedAttributes(si, new AttributeTable(
        unsignedAttrHash));

I think that's about it.

Here is how I got the signin-certificate attribute

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Attribute signingCertificateAttribute;
MessageDigest dig = MessageDigest.getInstance(DigestAlgorithm().getName(),
    new BouncyCastleProvider());

byte[] certHash = dig.digest(SigningCertificate().getEncoded());

if (DigestAlgorithm() == DigestAlgorithm.SHA1) {
    SigningCertificate sc = new SigningCertificate(new ESSCertID(certHash));

    signingCertificateAttribute = new Attribute(PKCSObjectIdentifiers.id_aa_signingCertificate, new DERSet(sc));

} else {
    ESSCertIDv2 essCert = new ESSCertIDv2(new AlgorithmIdentifier(DigestAlgorithm().getOid()), certHash);
    SigningCertificateV2 scv2 = new SigningCertificateV2(new ESSCertIDv2[] { essCert });

    signingCertificateAttribute =  new Attribute(PKCSObjectIdentifiers.id_aa_signingCertificateV2, new DERSet(scv2));
}

Hope it helps

Answer 1

CAdES is an extension of CMS (aka PKCS7), which is possible to do with BouncyCastle. RFC5126 contains everything needed for a CAdES signature, also, I recommend lookup info on ASN.1 since most of the parts are described in that format.

I am currently in hunt for the same answer you are looking for and found that the book Beginning Cryptography with Java by David Hook gives a lot of detailed information you might need.