We introduce dynamic watermarking techniques for protecting the value of intellectual property of CAD and compilation tools and reusable design components. The essence of the new approach is the addition of a set of design and timing constraints which encodes the author's signature. The constraints are selected in such a way that they result in a minimal hardware overhead while embedding a unique signature that is difficult to remove and forge. Techniques are applicable in conjunction with an

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... bitrary behavioral synthesis task such as scheduling, assignment, allocation, transformation, and template matching. On a large set of design examples, studies indicate the effectiveness of the new approach that results in signature data that is highly resilient, difficult to detect and remove, and yet is easy to verify and can be embedded in designs with very low hardware overhead. For example, the probability that the same design with the embedded signature is obtained by any other designers by themselves is less than 1 in 10 102 , and no register overhead was incurred. The probability of tampering, the probability that part of the embedded signature can be removed by random attempts, is shown to be extremely low, and the watermark is additionally protected from such tampering with error-correcting codes.