The invention provides a method of recovering from de-synchronization attacks includes registering original and altered digital content using nonlinear transformations to iteratively attempt to provide better-approximated registration. Approximation occurs at more than one level of granularity, by selecting among a greater number of possible transformation functions at each step. Transformations and comparisons might be conducted directly on pixel values, on coefficients for a set of basis wavelets, or on some transformation of the original and altered digital content. A human operator might assist this process, such as by suggesting transformations or providing evaluation of the degree of registration. Upon resynchronization, embedded identifying information in the original digital content is recovered.