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List:       bouncycastle-crypto-dev
Subject:    [dev-crypto] Re: Generating PKCS7 signature for S/MIME Signing
From:       champak <champak.83 () gmail ! com>
Date:       2011-11-15 9:52:34
Message-ID: 1321350754418-4042384.post () n4 ! nabble ! com
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Hello Valentina,

I have followed the below link also to generate a PKCS7.

http://stackoverflow.com/questions/5167174/problems-with-pkcs7-file-validation
http://stackoverflow.com/questions/5167174/problems-with-pkcs7-file-validation 

Below is the code that I have followed.
Sorry for the poor formatting.

import java.security.MessageDigest;
 import java.security.PrivateKey;
 import java.security.Signature; 
import java.security.cert.X509Certificate;
 import sun.security.pkcs.ContentInfo;
 import sun.security.pkcs.PKCS7;
 import sun.security.pkcs.PKCS9Attribute;
 import sun.security.pkcs.PKCS9Attributes;
 import sun.security.pkcs.SignerInfo;
 import sun.security.util.DerValue;
 import sun.security.x509.AlgorithmId;
 import sun.security.x509.X500Name;
  public class FirmaSun {     
 /*      * @param keyStore KeyStore Keystore that have got the certificate
to sign 
     * @param alias Name of certificate to sign, into the keystore     
 * @param datos byte to sign      
* @return String bytes that contains the PKCS7 created     
 */    
 public static OutputStream firmar(KeyStore keyStore, String alias, byte[]
datos) { 
         OutputStream salida = new ByteArrayOutputStream(); 
        String digestAlgorithm = "SHA1";       
  String signingAlgorithm = "SHA1withRSA";       
  PrivateKey priv = null;        
 X509Certificate x509 = null;        
  try {            
AlgorithmId[] digestAlgorithmIds = new
AlgorithmId[]{AlgorithmId.get(digestAlgorithm)};   
MessageDigest md = MessageDigest.getInstance(digestAlgorithm);          
md.update(datos);          
byte[] digestedContent = md.digest();           
PKCS9Attribute[] authenticatedAttributeList = {
        new PKCS9Attribute(PKCS9Attribute.CONTENT_TYPE_OID,
ContentInfo.DATA_OID), 
        new PKCS9Attribute(PKCS9Attribute.SIGNING_TIME_OID, new
java.util.Date()),   
        new PKCS9Attribute(PKCS9Attribute.MESSAGE_DIGEST_OID,
digestedContent)      
 };             
PKCS9Attributes authenticatedAttributes = new
PKCS9Attributes(authenticatedAttributeList);              x509 =
(X509Certificate) keyStore.getCertificateChain(alias)[0];         
   /* priv = (PrivateKey) keyStore.getKey(alias, null);     
         Signature signer = Signature.getInstance(signingAlgorithm);     
        signer.initSign(priv);        
     signer.update(authenticatedAttributes.getDerEncoding());  */
*<The above commented code is the original one. The below byte array is the
byte array returned value from the sign function of third party library >*
 byte[] signedAttributes =* <the output of sign function of third party
API.>* //signer.sign();       
ContentInfo contentInfo = null;         
contentInfo = new ContentInfo(ContentInfo.DATA_OID, new
DerValue(DerValue.tag_OctetString, datos));            
*The certficate is again obtained from the third party provider that is used
for signing *
X509Certificate[] certificates = {x509}; 
 java.math.BigInteger serial = x509.getSerialNumber();      
  SignerInfo si = new SignerInfo(new
X500Name(x509.getIssuerDN().getName()),serial,                   
  AlgorithmId.getAlgorithmId(digestAlgorithm),authenticatedAttributes,
 new  AlgogorithmId(AlgorithmId.RSAEncryption_oid),  signedAttributes,
null);
 SignerInfo[] signerInfos = {si};            
  PKCS7 p7 = new PKCS7( digestAlgorithmIds,
contentInfo,certificates,signerInfos);               
p7.encodeSignedData(salida);            
  //only for test the verify method          
   try {      
           p7.verify();           
  } 
catch (Exception e) {  
               System.out.println("Error en validacion:" + e.getMessage());   
              e.printStackTrace();           
  }         
 } catch (Exception ex) { 
            ex.printStackTrace();   
          return null;       
  }         
return salida;   
  }
 } 

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