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| 36. 43. 2. SHA MessageDigest |
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import java.io.FileInputStream;
import java.io.ObjectInputStream;
import java.security.MessageDigest;
public class MainClass {
public static void main(String args[]) throws Exception {
FileInputStream fis = new FileInputStream("test");
ObjectInputStream ois = new ObjectInputStream(fis);
Object o = ois.readObject();
if (!(o instanceof String)) {
System.out.println("Unexpected data in file");
System.exit(-1);
}
String data = (String) o;
System.out.println("Got message " + data);
o = ois.readObject();
if (!(o instanceof byte[])) {
System.out.println("Unexpected data in file");
System.exit(-1);
}
byte origDigest[] = (byte[]) o;
MessageDigest md = MessageDigest.getInstance("SHA");
md.update(data.getBytes());
if (MessageDigest.isEqual(md.digest(), origDigest))
System.out.println("Message is valid");
else
System.out.println("Message was corrupted");
}
}
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