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Java Security Signature Exception problem

Hi,
I'm having some problems with a piece of code that i'm trying to write where it throws a SignatureException - invalid encoding for signature.

- I declare the Signature as a 'global' variable.

- Before signing the message, I do the following:
sig = Signature.getInstance("DSA");
sig.initSign(PrivateKey);

- When I want to verify the signature, first I do this:
sig.initVerify(PublicKey);

The error is thrown right at the end when I come to the verification:
if (!sig.verify(sig))
      System.out.print("Signature NOT");
      System.out.print("Verified");

Anyone understand why I get an invalid coding message and what I should do to fix this?

Cheers,

Phil.

Mick Barry

where r you're key vars coming from?

phil8258

ASKER

Some code below:

// Declared in the main class:
public static PrivateKey PrivateKey = null;
public static PublicKey PublicKey = null;	
public static Signature sig = null;
 
//A bit of code from a method that creates the keys:
KeyPair keys = keypair.generateKeyPair();
PrivateKey = keys.getPrivate();
PublicKey = keys.getPublic();
 
//A bit of code from the method that signs the message:
sig = Signature.getInstance("DSA");
sig.initSign(PrivateKey);
 
//All of the above seems to work ok. Then...
 
//A bit of code from the method that verifies the signature:
sig.initVerify(PublicKey);
 
File f = new File("Input.txt");   //Open signed file
DataInputStream f = new DataInputStream(new FileInputStream(f));
 
byte[] sigTemp = new byte[SignedFile.read()];	//Read signed file into byte array
f.read(sigTemp, 0, f.read());
 
int length = (int) f.length();
byte[] Input = new byte[length];
f.read(Input, 0, length);
f.close();
 
sig.update(Input);
       
if (!sig.verify(sig))
              System.out.print("Signature NOT");
              System.out.print("Verified");
	}

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phil8258

ASKER

Error occurs at line 33 in the above code

Mick Barry

byte[] sigTemp = new byte[SignedFile.read()]; //Read signed file into byte array
f.read(sigTemp, 0, f.read());

whats that meant to be doing.
does not look like it would even compile

phil8258

ASKER

Good question!
I removed it, and the first thing that went wrong (or right) was that line 33 could no longer refer to sig
I changed line 33 to if (!sig.verify(Input))
and exception gone :O)

Only problem now is that its always reporting Signature Not Verified...
Changing to:

if (!signature.verify(Input)){
System.out.println("Signature not verified");
}
else {
System.out.println("Signature verified sucessfully");
}

and it still says "Signature not Verified"

Mick Barry

> if (!signature.verify(Input)){

the verify method expects the bytes of a signature, is that what Input contains?

phil8258

ASKER

Input contains:
0,ljaØÄaÉ"¼]~ÆSNxMQk[ªhzDÞ/mRyÒ¬!î=ïhÜHello World!

ASKER CERTIFIED SOLUTION

Mick Barry

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