  Visual cryptography aims to protect images against their possible
illegitimate use. Thus, one can cipher, hash, or add watermarks for protecting
copyright, among others. In this paper we provide a new solution to the problem
of secret sharing for the case when the secret is an image. Our method combines
the Shamir scheme for secret sharing using finite fields of characteristic 2
with the CBC mode of operation of a secure symmetric cryptographic scheme like
AES, so that the security relies on that of the mentioned techniques. The
resulting shares have the same resolution as that of the original image. The
idea of the method could be generalized to other multimedia formats like audio
or video, adapting the method to the corresponding encoded information.
