Method and system for scrambling and descrambling a digital image

A method for scrambling an original digital image into a scrambled image and for descrambling the scrambled image into a reconstructed image, said original image being defined, according to a coding format, by a set of orderly original coefficients which refer to coding elements arranged in blocks with in this image and/or to parameters of said coding format within a conversion table, the method comprising a scrambling operation and a descrambling operation;

• the scrambling operation comprising the steps of:
• substituting a plurality of said original coefficients by dummy coefficients of the same nature so as to safeguard said coding format;
• and
• storing the substituted original coefficients with their respective position, as original data into at least two control objects, each control object corresponding to a specific degradation level of the original image;
• the descrambling operation comprising the steps of:
• receiving the scrambled image and at least a part of said control objects;
• and
• using original data derived from a selection of at least one of said control objects, performed on the basis of a user access condition, for obtaining the reconstructed image by putting back the original coefficients instead of said dummy coefficients, by means of their respective position.