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 systems for
securing a data signal. Such systems may include computer devices for
applying a data reduction technique to reduce the data signal into a
reduced data signal and means to subtract the reduced data signal from
the data signal to produce a remainder signal. Such systems may include
means to apply a first cryptographic technique to encrypt the reduced
data signal to produce an encrypted, reduced data signal and 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.