A decoder for decoding coefficients of blocks of a video sequence from a bitstream, the decoder comprising: - a decoding module configured to decode a coefficient vector of each block from the bitstream, - a check module configured to reconstruct, for at least one block, hidden information from one or more coefficients of that block, the hidden information constituting or forming part of scan order information, SCAN_IDX, associated with that block, - a scan order selector configured to select a scan order for each block from a set of scan orders, on the basis of the scan order information, SCAN_IDX, associated with that block, and - a deserializer configured to inverse scan, for each block, the coefficient vector of that block according to the scan order selected for that block so as to obtain a coefficient matrix, wherein the check module is configured to reconstruct, for at least one block, the hidden information from at least one hiding coefficient vector chosen from the coefficient vector obtained for that block by applying a check-function to the hiding coefficient vector, a result of the check-function being the hidden information; and wherein the result of the check-function depends on coordinates (x, y), within the coefficient matrix, of the last significant coefficient of the hiding coefficient vector, particularly the check-function being the following function: mod x + y + R, 2 x and y being the coordinates, and R being an integer value. the decoder comprising: - a decoding module configured to decode a coefficient vector of each block from the bitstream, - a check module configured to reconstruct, for at least one block, hidden information from one or more coefficients of that block, the hidden information constituting or forming part of scan order information, SCAN_IDX, associated with that block, - a scan order selector configured to select a scan order for each block from a set of scan orders, on the basis of the scan order information, SCAN_IDX, associated with that block, and - a deserializer configured to inverse scan, for each block, the coefficient vector of that block according to the scan order selected for that block so as to obtain a coefficient matrix, wherein the check module is configured to reconstruct, for at least one block, the hidden information from at least one hiding coefficient vector chosen from the coefficient vector obtained for that block by applying a check-function to the hiding coefficient vector, a result of the check-function being the hidden information; and wherein the result of the check-function depends on coordinates (x, y), within the coefficient matrix, of the last significant coefficient of the hiding coefficient vector, - a decoding module configured to decode a coefficient vector of each block from the bitstream, - a check module configured to reconstruct, for at least one block, hidden information from one or more coefficients of that block, the hidden information constituting or forming part of scan order information, SCAN_IDX, associated with that block, - a scan order selector configured to select a scan order for each block from a set of scan orders, on the basis of the scan order information, SCAN_IDX, associated with that block, and - a deserializer configured to inverse scan, for each block, the coefficient vector of that block according to the scan order selected for that block so as to obtain a coefficient matrix, wherein the check module is configured to reconstruct, for at least one block, the hidden information from at least one hiding coefficient vector chosen from the coefficient vector obtained for that block by applying a check-function to the hiding coefficient vector, a result of the check-function being the hidden information; and wherein the result of the check-function depends on coordinates (x, y), within the coefficient matrix, of the last significant coefficient of the hiding coefficient vector, wherein the check module is configured to reconstruct, for at least one block, the hidden information from at least one hiding coefficient vector chosen from the coefficient vector obtained for that block by applying a check-function to the hiding coefficient vector, a result of the check-function being the hidden information; and wherein the result of the check-function depends on coordinates (x, y), within the coefficient matrix, of the last significant coefficient of the hiding coefficient vector, particularly the check-function being the following function: mod x + y + R, 2 x and y being the coordinates, and R being an integer value.