Generating RSA keys in PKCS#1 format in Java

Asked 2011-09-30T13:51:32.947

When I generate an RSA key pair using the Java API, the public key is encoded in the X.509 format and the private key is encoded in the PKCS#8 format. I'm looking to encode both as PKCS#1. Is this possible? I've spent a considerable amount of time going through the Java docs but haven't found a solution. The result is the same when I use the Java and the Bouncy Castle providers.

Here is a snippet of the code:

KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA","BC");
keygen.initialize(1024);
KeyPair pair = keygen.generateKeyPair();
PrivateKey priv = pair.getPrivate();
PublicKey pub = pair.getPublic();
byte[] privBytes = priv.getEncoded();
byte[] pubBytes = pub.getEncoded();

The two resulting byte arrays are formatted as X.509 (public) and PKCS#8 (private).

Any help would be much appreciated. There are some similar posts but none really answer my question.

Thank You

Edit Report

2 Answers

-1

The BouncyCastle framework has a PKCS1 Encoder to solve this: http://www.bouncycastle.org/docs/docs1.6/index.html

answered 2011-09-30T14:15:00.267

-1

I was trying to generate OpenSSL-friendly RSA public keys in DER format using BountyCastle J2ME library ported to BlackBerry, my code:

public void testMe() throws Exception {
  RSAKeyPairGenerator generator = new RSAKeyPairGenerator();
  generator.init(new RSAKeyGenerationParameters(BigInteger.valueOf(0x10001),
                 new SecureRandom(), 512, 80));
  AsymmetricCipherKeyPair keyPair = generator.generateKeyPair();

  RSAKeyParameters params =  (RSAKeyParameters) keyPair.getPublic();
  RSAPublicKeyStructure struct = new RSAPublicKeyStructure(params.getModulus(), 
                                                           params.getExponent());

  SubjectPublicKeyInfo info = 
    new SubjectPublicKeyInfo(new AlgorithmIdentifier("1.2.840.113549.1.1.1"), 
                             struct);

  byte[] bytes = info.getDEREncoded();

  FileOutputStream out = new FileOutputStream("/tmp/test.der");

  out.write(bytes);
  out.flush();
  out.close();
}

Key was still incorrect:

$ openssl asn1parse -in test.der -inform DER -i
0:d=0  hl=2 l=  90 cons: SEQUENCE          
2:d=1  hl=2 l=  11 cons:  SEQUENCE          
4:d=2  hl=2 l=   9 prim:   OBJECT            :rsaEncryption
15:d=1  hl=2 l=  75 prim:  BIT STRING

I changed org.bouncycastle.asn1.x509.AlgorithmIdentifier

public AlgorithmIdentifier(
    String     objectId)
{
    this.objectId = new DERObjectIdentifier(objectId);
    // This line has been added
    this.parametersDefined = true;
}

And now have nice key:

$ openssl asn1parse -in test.der -inform DER -i
0:d=0  hl=2 l=  92 cons: SEQUENCE          
2:d=1  hl=2 l=  13 cons:  SEQUENCE          
4:d=2  hl=2 l=   9 prim:   OBJECT            :rsaEncryption
15:d=2  hl=2 l=   0 prim:   NULL              
17:d=1  hl=2 l=  75 prim:  BIT STRING

Which can be used to encrypt:

$ echo "123" | openssl rsautl -pubin  -ink


                        
                        
                            answered 2012-01-03T11:39:52.440



        
        
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