Name: js151677 Date: 07/26/2004


FULL PRODUCT VERSION :
java version "1.5.0-beta3"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta3-b58)
Java HotSpot(TM) Client VM (build 1.5.0-beta3-b58, mixed mode, sharing)


ADDITIONAL OS VERSION INFORMATION :
Windows XP SP1
Windows 2000 SP4


A DESCRIPTION OF THE PROBLEM :
When using Java 1.5 if an RSA keypair is generated it has one less bit than requested, ie if a 512 bit keypair is requestedthen sometimes a 511 bit keypair is generated. There is no pattern to this - it affects all key sizes I have tried approximately 1 in 3 times.

This problem did not exist in Java 1.4.2.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
I have included source that will replicate the problem.


REPRODUCIBILITY :
This bug can be reproduced often.

---------- BEGIN SOURCE ----------
import java.math.BigInteger;
import java.security.*;
import java.security.spec.*;

/**
 * Class to prove RSA keysize bug in Java 1.5.
 *
 * @author Wayne Grant
 */
public class RsaBug extends Object
{
    public static void main(String[] sArgs)
    {
        try
        {
            for (int iCnt=0; iCnt < 10; iCnt++)
            {
int iKeyPairSize = 512;

System.out.println("Generating " + iKeyPairSize + " bit RSA key pair");

// Generate RSA keypair
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
SecureRandom rand = SecureRandom.getInstance("SHA1PRNG");
keyPairGen.initialize(iKeyPairSize, rand);
KeyPair keyPair = keyPairGen.generateKeyPair();

// Get priavte and public keys
PrivateKey privateKey = keyPair.getPrivate();
PublicKey publicKey = keyPair.getPublic();

// Get keysize (modulus) of keys
KeyFactory keyFact = KeyFactory.getInstance("RSA");

RSAPrivateKeySpec privateKeySpec = (RSAPrivateKeySpec)keyFact.getKeySpec(privateKey, RSAPrivateKeySpec.class);
BigInteger privateModulus = privateKeySpec.getModulus();
int iPrivateKeySize = privateModulus.toString(2).length();

RSAPublicKeySpec publicKeySpec = (RSAPublicKeySpec)keyFact.getKeySpec(publicKey, RSAPublicKeySpec.class);
BigInteger publicModulus = publicKeySpec.getModulus();
int iPublicKeySize = publicModulus.toString(2).length();

System.out.println("Generated a " + iPrivateKeySize + " bit RSA private key");
System.out.println("Generated a " + iPublicKeySize + " bit RSA public key");

if ((iKeyPairSize != iPublicKeySize) || (iKeyPairSize != iPrivateKeySize))
{
System.out.println("Failure!");
break;
}
            }
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }
}

---------- END SOURCE ----------

Release Regression From : 1.4.2_04
The above release value was the last known release where this
bug was known to work. Since then there has been a regression.

(Incident Review ID: 289826)
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