AES输入数据加解密仿真-源码

function plaintext = inv_cipher (ciphertext, w, inv_s_box, inv_poly_mat, vargin) %INV_CIPHER Convert 16 bytes of ciphertext to 16 bytes of plaintext. % % PLAINTEXT = INV_CIPHER (CIPHERTEXT, W, INV_S_BOX, INV_POLY_MAT) % converts CIPHERTEXT (back) to the plaintext PLAINTEXT, % using the expanded cipher key W, % the inverse byte substitution table INV_S_BOX, and % the inverse transformation matrix INV_POLY_MAT. % % PLAINTEXT = INV_CIPHER (CIPHERTEXT, W, INV_S_BOX, INV_POLY_MAT, 1) % switches verbose mode on, that displays intermediate results. % CIPHERTEXT has to be a vector of 16 bytes (0 <= CIPHERTEXT(i) <= 255). % W has to be a [44 x 4]-matrix of bytes (0 <= W(i,j) <= 255). % Copyright 2001-2005, J. J. Buchholz, Hochschule Bremen, buchholz@hs-bremen.de % Version 1.0 30.05.2001 % If there is an optional "verbose mode" argument if nargin > 4 % Switch the verbose mode flag on verbose_mode = 1; % If there is no optional "verbose mode" argument else % Switch the verbose mode flag off verbose_mode = 0; end % If the input vector is a cell array or does not have 16 elements if iscell (ciphertext) | prod (size (ciphertext)) ~= 16 % Inform user and abort error ('Ciphertext has to be a vector (not a cell array) with 16 elements.') end % If any element of the input vector cannot be represented by 8 bits if any (ciphertext < 0 | ciphertext > 255) % Inform user and abort error ('Elements of ciphertext vector have to be bytes (0 <= ciphertext(i) <= 255).') end % If the expanded key array is a cell arrray or does not have the correct size if iscell (w) | any (size (w) ~= [44, 4]) % Inform user and abort error ('w has to be an array (not a cell array) with [44 x 4] elements.') end % If any element of the expanded key array can not be represented by 8 bits if any (w < 0 | w > 255) % Inform user and abort error ('Elements of key array w have to be bytes (0 <= w(i,j) <= 255).') end % Display headline if requested if verbose_mode disp (' ') disp ('********************************************') disp ('* *') disp ('* I N V E R S E C I P H E R *') disp ('* *') disp ('********************************************') disp (' ') end % Copy the 16 elements of the input vector column-wise into the 4 x 4 state matrix state = reshape (ciphertext, 4, 4); % Display intermediate result if requested if verbose_mode disp_hex ('Initial state : ', state) end % Copy the last 4 rows (4 x 4 elements) of the expanded key % into the current round key. % Transpose to make this column-wise round_key = (w(41:44, :))'; % Display intermediate result if requested if verbose_mode disp_hex ('Initial round key : ', round_key) end % Add (xor) the current round key (matrix) to the state (matrix) state = add_round_key (state, round_key); % Loop over 9 rounds backwards for i_round = 9 : -1 : 1 % Display intermediate result if requested if verbose_mode disp_hex (['State at start of round ', num2str(i_round),' : '], state) end % Cyclically shift the last three rows of the state matrix state = inv_shift_rows (state); % Display intermediate result if requested if verbose_mode disp_hex ('After inv_shift_rows : ', state) end % Substitute all 16 elements of the state matrix % by shoving them through the S-box state = sub_bytes (state, inv_s_box); % Display intermediate result if requested if verbose_mode disp_hex ('After inv_sub_bytes : ', state) end % Extract the current round key (4 x 4 matrix) from the expanded key round_key = (w((1:4) + 4*i_round, :))'; % Display intermediate result if requested if verbose_mode disp_hex ('Round key : ', round_key) end % Add (XOR) the current round key (matrix) to the state (matrix) state = add_round_key (state, round_key); % Display intermediate result if requested if verbose_mode disp_hex ('After add_round_key : ', state) end % Transform the columns of the state matrix via a four-term polynomial. % Use the same function (mix_columns) as in cipher, % but with the inverse polynomial matrix state = mix_columns (state, inv_poly_mat); end % Display intermediate result if requested if verbose_mode disp_hex ('State at start of final round : ', state) end % Cyclically shift the last three rows of the state matrix state = inv_shift_rows (state); % Display intermediate result if requested if verbose_mode disp_hex ('After inv_shift_rows : ', state) end % Substitute all 16 elements of the state matrix % by shoving them through the inverse S-box state = sub_bytes (state, inv_s_box); % Display intermediate result if requested if verbose_mode disp_hex ('After inv_sub_bytes : ', state) end % Extract the "first" (final) round key (4 x 4 matrix) from the expanded key round_key = (w(1:4, :))'; % Display intermediate result if requested if verbose_mode disp_hex ('Round key : ', round_key) end % Add (xor) the current round key (matrix) to the state (matrix) state = add_round_key (state, round_key); % Display intermediate result if requested if verbose_mode disp_hex ('Final state : ', state) end % reshape the 4 x 4 state matrix into a 16 element row vector plaintext = reshape (state, 1, 16);