Criptografia usando CMS

JavaGuru Membro desde: 22/02/2005 19:46:49 Mensagens: 205 Offline

Boa tarde pessoal,

Estou quase lá na minha classe q criptografa e descriptografa usando CMS enveloped data.
O seguinte código q obtive até agora irei compartilha-lo com vcs para me ajudarem a descobrir o q pode ser feito pra corrigir a Exception "too much data for RSA block".

public class CMSteste {
	
	private KeyStore keystore;
	
	private static BASE64Encoder b64Encoder = new BASE64Encoder();
	private static BASE64Decoder b64Decoder = new BASE64Decoder();
	
	public static void main(String [] args) throws Exception {
		
		String ksName = "C:\\Documents and Settings\\tfreitas\\keystore.ks";
		String alias = "CN=Makrocert Public Primary CA,7B357AE5000000000139";            
		String password = "minhasenha";
		String infile = "C:\\teste\\criptoTestes\\file.txt";
		String outfile = "C:\\teste\\criptoTestes\\filecrip.txt";
		String decfile = "C:\\teste\\criptoTestes\\filedecrip.txt";
		
		CMSteste sealed = new CMSteste(ksName, password);
		
		
		sealed.encrypt(alias, infile, outfile);
		
		sealed.decrypt(alias, password, outfile, decfile);
		
		
	}
	
	public CMSteste() throws Exception {   
						
		//Pegando o Certificado		
		IUtilBuscaCertificados iuc = UtilBuscaCertificado.getInstancia();

//pega o certificado pelo email
		X509Certificate certificadoNoToken = 	iuc.getCertificadoPeloEmail("meuemail@hotmail.com.br");	
			
		//pega o keystore passando o provider da Assembla
		this.keystore = KeyStore.getInstance("msks", UtilCertificados.getProvider());
		this.keystore.load(null, null); 		
	}	
	
	public void encrypt(String alias, String infile, String outfile) throws Exception {
		
		// get certificate out of keystore
		Certificate c = this.keystore.getCertificate(alias);
		X509Certificate x509 = (X509Certificate) c;
		
		// read in list from file
		BufferedReader reader = new BufferedReader(new FileReader(infile));
		
		// file should be ...   
		ArrayList list = new ArrayList();
		String line = null;
		while ((line = reader.readLine()) != null) {
			list.add(line);
		}
		String[] array = (String[]) list.toArray(new String[0]);
		
		
		// turn String[] object into a byte array
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		ObjectOutputStream oos = new ObjectOutputStream(baos);
		oos.writeObject(array);
		oos.flush();
		oos.close();
		byte[] arrayAsBytes = baos.toByteArray();
		
		CMSEnvelopedDataGenerator edGen = new CMSEnvelopedDataGenerator();
		edGen.addKeyTransRecipient(x509);
		
		
		CMSEnvelopedData cmsed = null ;
		
		// encrypt byte[] in CMS
		cmsed =
			edGen.generate(
					new CMSProcessableByteArray(arrayAsBytes),
					CMSEnvelopedDataGenerator.AES256_CBC, "BC");
		
		
		
		byte[] asn1Bytes = cmsed.getEncoded();
		
		// turn ASN.1 byte[] into a base64 String
		String b64Array = b64Encoder.encode(asn1Bytes);
		
		PrintWriter writer = new PrintWriter(new FileOutputStream(outfile));
		writer.write(b64Array);
		writer.flush();
		writer.close();
	}
	
	public void decrypt(String alias, String password, String infile, String outfile) throws Exception {
		
		Key k = this.keystore.getKey(alias, password.toCharArray());
		RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) k;
		
		BufferedReader reader = new BufferedReader(new FileReader(infile));
		
		// read base64 CMS data from file
		String line = null;
		StringBuffer sb = new StringBuffer();
		while ((line = reader.readLine()) != null) {
			sb.append(line);
		}
		
		// get ASN.1 bytes from base64
		byte [] asn1Bytes = b64Decoder.decodeBuffer(sb.toString());
		
		CMSEnvelopedData cmsed = new CMSEnvelopedData(asn1Bytes);
		RecipientInformationStore  recipients = cmsed.getRecipientInfos();
		Collection c = recipients.getRecipients();
		Iterator it = c.iterator();
		byte[] recData = null;
		while (it.hasNext()) {
			RecipientInformation recipient = (RecipientInformation)it.next(); 			
			
			
			// get decrypted byte[]
//------AQUI Q DA ERROOOOO ERROOOOOOOO--------
			recData = recipient.getContent(rsaPrivateKey, "BC");

}
		
		// transform byte[] back into original object: String[]
		ByteArrayInputStream bais = new ByteArrayInputStream(recData);
		ObjectInputStream ois = new ObjectInputStream(bais);
		String[] array = (String[]) ois.readObject();
		
		PrintWriter writer = new PrintWriter(new FileOutputStream(outfile));
		for (int i = 0, n = array.length; i < n; i++) {
			writer.println(array[i]);        
		}        
		writer.flush();        
		writer.close();       
	}
}

Preciso urgente de ajuda com isso. Até agora já descobri q o erro ocorre por q tentamos descriptografar algo maior q minha chave RSA. E isso gera uma excessao segundo o q disse esse cara num forum. "BouncyCastle RSA gives an exception if you try to encrypt a block
which is longer than the key size. In your case the key size is 512
== 64 bytes. I think the only work around is to break your text into
64 byte blocks."

Alguem me ajuda???

Desde já agradeço à atenção!

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