Introduction to Digital Water Marking Seminar:
Dynamic Watermarking Techniques
Dynamic watermarks are constructed at runtime and stored in the dynamic state of the program and were only introduced recently.
There are three kinds of dynamic watermarks. In each case, the mark is given by running the program with a predetermined input sequence. There are three dynamic watermarking techniques:
Easter egg Watermarks: when the special input sequence is entered, it performs action that is requested by the user
Execution Trace Water: The watermark is embedded within the trace with no special output.
Data Structure Watermarks: The watermark is embedded within the state of the program with the special input I and doesn’t provide any output.
There are many situations where we want to stop a one from executing our program if it has been altered in any way. For e.g., a program P should not be allowed to run if
1) P is watermarked and the code that builds the mark has been altered, 2) A virus has been attached to P, or 3) P is an e-commerce application and the security-sensitive part of its code has been modified. To prevent such tampering attacks we can add tamper-proofing code to our program. This code should
a) Detect if the program has been altered and b) Cause the program to fail when tampering is done.
There are three principal ways to detect tampering:
1. We can compare the executable program itself is identical to the original one. To speed up the test, a message-digest algorithm can be used.
2. We can examine the intermediate results produced by the program. This technique is known as program (or result) checking.
3. We can encrypt the executable, thereby preventing anyone from modifying it unless they are able to decrypt it.
Tamper-proofing of type-safe distribution formats such as Java byte code is more difficult than tamper-proofing assembly code.
3.1 Tamper-Proofing Viruses
A virus writer uses many techniques to protect a virus from detection and tamper-proofing-like techniques so that it cannot be easily removed from the infected host program. Armored viruses add extra code to a virus to make it difficult to analyze.
Download Seminar on Digital Watermarking and Tamper Proofing Tools Report .