Re: Same text, different Signature with each execution

Anyone? :-(

El sábado, 30 de marzo de 2013 18:27:32 UTC+1, Manuel Alejandro Fernandez Casado escribió:

Hi.

I´m using GWT 2.5 and I´m trying to sign a text, that is always the same.

Code (exceptions ommited):

public String sign(String text) {

String sign = null;

Signature signer = Signature.getInstance("SHA1withRSA");

signer.initSign(privKey);

signer.update(text.getBytes());

sign = Base64Utils.toBase64(signer.sign());

return sign;

}

I put some System.out.println to see values. First are 8 first bytes from clear text (variable text). Second is clear text passed to base64 using Base64Utils (just in case Base64Utils returns different values). Third is 8 first bytes from signed text. 

I put different executions:

Execution 1

  

50,57,54,35,49,35,49,51

MjI5NiMxIzEzNjU4Mzk0OTc5MzIjU0hBMXdpdGhSU0EjMTI3LjAuMC4xI3R1c2N1aWRhZG9yZXMuY29tIw==

11,82,116,126,85,-101,80,94

Execution 2

 50,57,54,35,49,35,49,51

MjI5NiMxIzEzNjU4Mzk0OTc5MzIjU0hBMXdpdGhSU0EjMTI3LjAuMC4xI3R1c2N1aWRhZG9yZXMuY29tIw==

-110,27,121,116,7,-99,-78,56

Execution 3

 50,57,54,35,49,35,49,51

MjI5NiMxIzEzNjU4Mzk0OTc5MzIjU0hBMXdpdGhSU0EjMTI3LjAuMC4xI3R1c2N1aWRhZG9yZXMuY29tIw==

33,-77,-128,14,-24,-38,93,124

 

I can´t put private key but I can assure you (breakpoint see) that is always the same.

So problem is clear. The method Signature.getInstance is returning a different Signature construction that makes signed text different each time.

Does anyone know why this happens?

Thanks in advance.

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