The present invention relates to methods for protecting a data signal
using the following techniques: applying a data reduction technique to
reduce the data signal into a reduced data signal; subtracting the
reduced data signal from the data signal to produce a remainder signal;
embedding a first watermark into the reduced data signal to produce a
watermarked, reduced data signal; and adding the watermarked, reduced
data signal to the remainder signal to produce an output signal. A second
watermark may be embedded into the remainder signal before the final
addition step. Further, cryptographic techniques may be used to encrypt
the reduced data signals and to encrypt the remainder signals before the
final addition step. The present invention also relates to a system for
securing a data signal including: computer devices for applying a data
reduction technique to reduce the data signal into a reduced data signal;
means to subtract the reduced data signal from the data signal to produce
a remainder signal; means to apply a first cryptographic technique to
encrypt the reduced data signal to produce an encrypted, reduced data
signal; means to apply a second cryptographic technique to encrypt the
remainder signal to produce an encrypted remainder signal; and means to
add the encrypted, reduced data signal to the encrypted remainder signal
to produce an output signal.