there is no standard API in Java for handling PKCS#7. you have to use a
proprietary API for this purpose.
you may have a look at our IAIK-JCE toolkit. for non-commercial use it is
for free. commercial licenses are available.
you can get an evaluation copy from
http://jce.iaik.tugraz.at/download/evaluation/index.php (first register for
free).

a piece of code creating a SignedData as you need it would look something
like this:

 byte[] data = ...;
 SignedData signedData = new SignedData(data, SignedData.IMPLICIT);
 signedData.setCertificates(new X509Certificate[] { signerCertificate } );
 IssuerAndSerialNumber signerIssuerAndSerialNumber = new
IssuerAndSerialNumber(signerCertificate);
 SignerInfo signerInfo = new SignerInfo(signerIssuerAndSerialNumber,
AlgorithmID.sha1, signatureKey);
 signedData.addSignerInfo(signerInfo);
 byte[] encoding = signedData.getEncoded();

regards

 Karl Scheibelhofer

--

Karl Scheibelhofer, IAIK - Graz University of Technology
Inffeldgasse 16a, 8010 Graz, Austria
Fax: +43 316 873 5520
http://jce.iaik.tugraz.at/
Visit us at the RSA conference in San Francisco, 14-18 Feb 2005, booth 438