Examples for Using Digital Signatures

Digitally Signing a Document

The following examples show how to digitally sign a document using the digital signature interfaces for XML. The data to sign is contained in the file input.xml . The private key used to sign is located in the DEFAULT keystore view, under the alias sign_test .

Creating an Object From the Data

Before you can sign the data, you must create an object using the interface ISsfData as shown in the example below.

Code Example for Creating an Object for the Data to Sign

//  open test data file
FileInputStream  fis  =  null;
try  {    
    fis  =  new  FileInputStream("input.xml");    
} catch  (FileNotFoundException  e)  {        
    System.out.println("Error while opening input file " + e);        
    System.exit(1);    
}    
// create object of ssf data 
ISsfData  data  =  null;
try  {    
    data  =  new  SsfDataXML(fis);    
} catch  (Exception  e)  {        
    System.out.println("Error while reading input file " + e);        
    System.exit(1);    
}

Obtaining the Profile and Signing the Data

Once you have an object for the data, you must obtain the private key to use for signing, which is contained in the designated profile. The example below shows how to obtain the profile, which is stored in the DEFAULT keystore view, alias sign_test . It also shows how to use the sign method to sign the data. It writes the signed data to the file output.xml .

Code Example for Obtaining the Profile and Signing the Data

// get profile from keystore service of AS Java
InitialContext  ctx  =  ctx  =  new  InitialContext();
Object  o  =   (Object)  ctx.lookup("keystore");
KeystoreManager  manager  =   (KeystoreManager)  o;
keyStore  =  manager.getKeystore("DEFAULT");     
String  alias  =  "sign_test";        
try  {    
    profile  =  new  SsfProfileKeyStore(keyStore,  alias,  null);
} catch  (Exception  e)  {    
    throw  new  SecurityException("Error while accessing keystore " + e);
}               
// sign the data 
try  {    
    res  =  data.sign(profile);
} catch  (SsfInvalidKeyException  e)  {    
    System.out.println("Error while signing data " + e);    
    System.exit(1);             
}
if  (!res)  {    
    System.out.println("Creation of signature failed");    
    System.exit(1);                 
}                
// write the signed data 
FileOutputStream  fos  =  null;
try  {    
    fos  =  new  FileOutputStream("output.xml");    
    data.writeTo(fos);
} catch  (Exception  e)  {    
    System.out.println("Error while opening output file " + e);    
    System.exit(1);
}       
System.out.println("Created output file OK");

Verifying the Digital Signature

The following example shows how to verify a digital signature. The signed data is contained in the file output.xml . First, we create an object for this data. Then, we obtain the public address book, which is also located in the keystore view DEFAULT , alias verify_test . The public address book contains the public-key certificate belonging to the signer that is used to verify. Then, we show how to use the verify method to verify the digital signature.

Code Example for Obtaining the Profile and Signing the Data

// open signed data file
FileInputStream  fis  =  null;
try  {    
    fis  =  new  FileInputStream("output.xml");    
} catch  (FileNotFoundException  e)  {        
    System.out.println("Error while opening signed file " + e);        
    System.exit(1);    
}     // create object of ssf data 
ISsfData  data  =  null;
try  {    
    data  =  new  SsfDataXML(fis);    
} catch  (Exception  e)  {        
    System.out.println("Error while reading signed file " + e);        
    System.exit(1);    
}
// get pab from keystore service of AS Java 
InitialContext  ctx  =  new  InitialContext();
Object  o  =   (Object)  ctx.lookup("keystore");
KeystoreManager  manager  =   (KeystoreManager)  o;
keyStore  =  manager.getKeystore("DEFAULT");     
String  alias  =  "verify_test";        
try  {    
    pab  =  new  SsfPabKeyStore(keyStore);
} catch  (Exception  e)  {    
    throw  new  SecurityException("Error while accessing keystore " + e);
}       
// verify the data 
SsfSigRcpList  signer  =  new  SsfSigRcpList();
try  {    
    res  =  data.verify(pab, signer);
} catch  (SsfInvalidDataException  e)  {    
    System.out.println("Error while verifying data " + e);    
    System.exit(1);                 
}        
// print result of verification 
if  (res)  {    
    System.out.println("Verification of data OK");    
    if  (signer.get(0).rc  ==  SsfSigRcpInfo.SSF_OK)  {        
        X509Certificate  cert  =  signer.get(0).cert;        
        System.out.println("Signer: " + cert.getSubjectDN().getName());    
    }           
} else  {    
    System.out.println("Verification of data FAILED");
}