Method for concealing data in an image or a video stream inside a compression chain

A method for concealing data in an image or a video stream inside a compression chain, this method being implemented by computer and comprising the following steps:

• a phase of structuring and processing during which at least one image is structured in blocks containing coefficients;
• a phase of transformation and quantization of the blocks so as to generate transformed and quantized coefficients;
• an entropy encoding intended to encode the transformed and quantized coefficients;
• a data concealment step during which bits from the data are concealed by modifying transformed and quantized coefficients, situated in a zone of high frequencies of at least a part of said blocks which are relative to the luminance component of the video stream and which are intra-coded,
• in that this modification is carried out after the quantization but before the entropy encoding;
• and for a predefined concealment level k, k being comprised between 1 and N−1 for a block of size N×N, the modification applies only to the coefficients aligned below a diagonal concealment level taken across the N×N block.