CSharp to Java RSA Conversion

RealistSpy

Hi all,

I am trying to convert a code from c# to java but I am so lost with java, well a little.

The problem:
in C# I can manually put in what I want.

byte[] key = //array

RSAParameters RSAkey = new RSAParameters();
RSAkey.D = key;
RSAkey.Modulus = 
RSAkey.P =
RSAkey.Q =
RSAkey.DP = 
RSAkey.DQ =

In java I dont seem to have that option and I don't want to generate random keys.

Thanks in advance.

srsly78

Library dependent.

RealistSpy

srsly78 wrote: »

Library dependent.

what Library ?

RealistSpy

This is the Library/Package that I need : Link
but how do I import it?

srsly78

import org.cheez.burger;

Your questions are extremely vague. Specify what IDE etc you are using.

Procasinator

You don't need additional libraries, it is all built into Java. You just got too look for the correct interfaces/classes.

For instance, look at the constructor for this class:
http://download.oracle.com/javase/1.4.2/docs/api/java/security/spec/RSAPrivateCrtKeySpec.html

RealistSpy

Procasinator wrote: »

You don't need additional libraries, it is all built into Java. You just got too look for the correct interfaces/classes.

For instance, look at the constructor for this class:
http://download.oracle.com/javase/1.4.2/docs/api/java/security/spec/RSAPrivateCrtKeySpec.html

i don't know how I miss that well I know but [FacePalm]

Anyways c# Code

RSAParameters RSAkey = new RSAParameters();
RSAkey.D = key;
RSAkey.Modulus = 
RSAkey.P =
RSAkey.Q =
RSAkey.DP = 
RSAkey.DQ =

//System.Security.Cryptography.RSAParameters

Java Code representation

RSAkey.D = PrivateExponent
RSAkey.Modulus = Modulus
RSAkey.P = PrimeP
RSAkey.Q = PrimeQ
RSAkey.DP = PrimeExponentP
RSAkey.DQ = PrimeExponentQ
RSAkey.Exponent = PublicExponent
RSAkey.InverseQ = CrtCoeficent

//java.security.spec.RSAPrivateCrtKeySpec

RealistSpy

Hi,
I am back again
How can I recode this to java

public static byte[] signatureGenerate(RSAParameters param, byte[] hash)
        {
            RSACryptoServiceProvider cryptoRSA = new RSACryptoServiceProvider();
            RSAPKCS1SignatureFormatter sigFormatRSA = new RSAPKCS1SignatureFormatter();
            cryptoRSA .ImportParameters(param); 

            sigFormatRSA .SetHashAlgorithm("SHA1");
            sigFormatRSA .SetKey(cryptoRSA );

This is what I have so far

public static byte[] SignatureGenerate(RSAPrivateCrtKeySpec param, byte[] hash)
    {
        try
        {
            //works but I want to use RSAPrivateCrtKeySpec  and I dont want to generate one
            KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
            
            KeyPair keyPair = kpg.generateKeyPair();
            PrivateKey priv1 = keyPair.getPrivate();
            
            Signature signature1 = Signature.getInstance("SHA1withRSA");
            signature1.initSign(priv1);
            signature1.update(hash);
            
            return signature1.sign();

            //Dont work
            //KeyFactory kf = KeyFactory.getInstance("RSA");
            //PrivateKey priv = kf.generatePrivate(param);
            
            //Signature signature = Signature.getInstance("SHA1withRSA");
            //signature.initSign(priv);
            
            //return signature.sign();
        }

lynchie

I think you can use the KeyFactory class to generate a PrivateKey instance from your RSAPrivateCrtKeySpec which you can then use in the initSign() method.

KeyFactory kf = KeyFactory.getInstance("RSA");
PrivateKey myPrivateKey = kf.generatePrivate(param);

RealistSpy

lynchie wrote: »

I think you can use the KeyFactory class to generate a PrivateKey instance from your RSAPrivateCrtKeySpec which you can then use in the initSign() method.

KeyFactory kf = KeyFactory.getInstance("RSA");
PrivateKey myPrivateKey = kf.generatePrivate(param);

Doesn't work. Data cannot sign error.

RealistSpy

My goal is to:
Generate a PKS1 Signature of SHA1 digest(hash)
using specified RSAParameters (param) to generate a private key
(param) contains: BigInteger
D = PrivateExponent
Modulus = Modulus
P = PrimeP
Q = PrimeQ
DP = PrimeExponentP
DQ = PrimeExponentQ
Exponent = PublicExponent
InverseQ = CrtCoeficent ????

I manage to get everything working fine in c# but I cant seem to get it working on java. Java generates a key but I get error (Cannot sign Data) when I try to sign the signature.

If I use random key generation in java I get no error but the file gets corrupted

Procasinator

Make sure you are creating the key correctly. Test with known working inputs for each of the RSAPrivateCrtKeySpec.

Also, consider using RSAPrivateKeySpec as you probably only need the private exponent and the modulus anyhow.

RealistSpy

Procasinator wrote: »

Make sure you are creating the key correctly. Test with known working inputs for each of the RSAPrivateCrtKeySpec.

Also, consider using RSAPrivateKeySpec as you probably only need the private exponent and the modulus anyhow.

Still can't get it to sign. I will keep trying fingers crossed