Question

我的AES算法适用于文本，但是当我尝试将其调整为图像时，它仍然无效。对我来说似乎都是合乎逻辑的，无法找到麻烦的地方。谢谢这是主程序，我将矩阵分成4x4子矩阵然后我使用aesencrypt / aesdecrypt函数（这个函数也适用于文本）

  function [encrypt] = aes(s, oper, mode, I, iv, sbit)switch lower(oper)
        case {'encrypt', 'enc', 'e'}
            oper = 0;
        case {'decrypt', 'dec', 'd'}
            oper = 1;
        otherwise
            error('Bad ''oper'' parameter.');
    end

    E.sub_mat=[];
    E.final=[];
    [m n]=size(I);
    p=m/4*n/4;
    k=1;
    %Splite the image matrix into 4*4 sub matrix
    for j=1:4:m
        for i=1:4:n
            E.sub_mat{k}=imcrop(I,[i,j,3,3]);
            k=k+1;
        end
    end

    input =zeros(4,4,'double');
    blocks=p;
    l=1;
    for l=1:blocks
    input = E.sub_mat{l};
    switch lower(mode)

        case {'ecb'}
            % Electronic Codebook Mode
            % ------------------------
            output = zeros(4,4,'double');

                if (oper)
                    % decrypt
                    output = aesdecrypt(s,input);
                else
                    % encrypt
                    output = aesencrypt(s,input);
                end    

            % Dites ceci est la matrice donnée:



        case {'cbc'}
            % Cipher Block Chaining Mode
            % --------------------------
            if (nargin < 5)
                error('Missing initialization vector ''iv''.');
            end
            output = zeros(4,4,'double');
            ob = iv;

                if (oper)
                    % decrypt
                    in = input;
                    output = bitxor(ob(:), aesdecrypt(s,in)');
                    ob = in;
                else
                    % encrypt
                    ob = bitxor(ob(:), input(idx));
                    ob = aesencrypt(s, ob);
                    output = ob;
                end


            % store iv for block passing
            s.iv = ob;


        case {'cfb'}
            % Cipher Feedback Mode
            % --------------------
            % Special mode with bit manipulations
            % sbit = 1..128
            if (nargin < 6)
                error('Missing ''sbit'' parameter.');
            end
            % get number of bits
            input=input(:);
            bitlen = 8*length(input);
            % loop counter
            rounds = round(bitlen/sbit);
            % check 
            if (rem(bitlen, sbit))
                error('Message length in bits is not multiple of ''sbit''.');
            end
            % convert input to bitstream
            inputb = reshape(de2bi(input,8,2,'left-msb')',1,bitlen);
            % preset init. vector
            ib = iv;
            ibb = reshape(de2bi(ib,8,2,'left-msb')',1,128);
            % preset output binary stream
            outputb = zeros(size(inputb));
            for i = 1:rounds
                iba = aesencrypt(s, ib);
                % convert to bit, MSB first
                ibab = reshape(de2bi(iba,8,2,'left-msb')',1,128);
                % strip only sbit MSB bits
                % this goes to xor
                ibab = ibab(1:sbit);
                % strip bits from input
                inpb = inputb((i - 1)*sbit + (1:sbit));
                % make xor
                outb = bitxor(ibab, inpb);
                % write to output
                outputb((i - 1)*sbit + (1:sbit)) = outb;
                if (oper)
                    % decrypt
                    % prepare new iv - bit shift
                    ibb = [ibb((1 + sbit):end) inpb];
                else
                    % encrypt
                    % prepare new iv - bit shift
                    ibb = [ibb((1 + sbit):end) outb];
                end
                % back to byte ary
                ib = bi2de(vec2mat(ibb,8),'left-msb');
                % loop
            end
            output = bi2de(vec2mat(outputb,8),'left-msb');
            % store iv for block passing
            s.iv = ib;
            output=reshape(output,4,4);

        case {'ofb'}
            % Output Feedback Mode
            % --------------------
            if (nargin < 5)
                error('Missing initialization vector ''iv''.');
            end
            output = zeros(4,4,'double');
            ib = iv;

                % encrypt, decrypt
                ib = aesencrypt(s, ib);
                output = bitxor(ib(:), input);

            % store iv for block passing
            s.iv = ib;

        case {'ctr'}
            % Counter Mode
            % ------------
            if (nargin < 5)
                iv = 1;
            end
            input=input(:);
            output = zeros(1,length(input));
            idx = 1:16;
            for i = (iv):(iv + blocks - 1)
                ib = AES_GET_COUNTER(i);
                ib = aesencrypt(s, ib);
                output(idx) = bitxor(ib(:), input(idx));
                idx = idx + 16;
            end
            s.iv = iv + blocks;
            output=reshape(output,4,4);
        otherwise
            error('Bad ''oper'' parameter.');
    end
    E.final{l}=output;
    end
    encrypt=zeros(m,n,'double');
    a=1;
    for i=1:(m/4)
        for j=1:(n/4)
            r2=4*i;r1=r2-3;
            c2=4*j;c1=c2-3;    
            encrypt(r1:r2,c1:c2)=E.final{a}; 
            a=a+1;
        end
    end

aesencrypt功能

function [out] = aesencrypt（s，in） state = in;

% Initial round
% AddRoundKey keyexp(1:4)
state = bitxor(state, (s.keyexp(1:4, :))');

% Loop over (s.rounds - 1) rounds
for i = 1:(s.rounds - 1)
    % SubBytes - lookup table
    state = s.s_box(state + 1);
    % ShiftRows
    state = shift_rows(state, 0);
    % MixColumns
    state = mix_columns(state, s);
    % AddRoundKey keyexp(i*4 + (1:4))
    state = bitxor(state, (s.keyexp((1:4) + 4*i, :))');
end

% Final round
% SubBytes - lookup table
state = s.s_box(state + 1);
% ShiftRows
state = shift_rows(state, 0);
% AddRoundKey keyexp(4*s.rounds + (1:4))
state = bitxor(state, (s.keyexp(4*s.rounds + (1:4), :))');
out = state;

aesdecrypt功能

function [out] = aesdecrypt(s, in)state = in;

% Initial round
% AddRoundKey keyexp(s.rounds*4 + (1:4))
state = bitxor(state, (s.keyexp(s.rounds*4 + (1:4), :))');

% Loop over (s.rounds - 1) rounds
for i = (s.rounds - 1):-1:1
    % ShiftRows
    state = shift_rows(state, 1);
    % SubBytes - lookup table
    state = s.inv_s_box(state + 1);
    % AddRoundKey keyexp(i*4 + (1:4))
    state = bitxor(state, (s.keyexp((1:4) + 4*i, :))');
    % MixColumns
    state = mix_columns(state, s);
end

% Final round
% ShiftRows
state = shift_rows(state, 1);
% SubBytes - lookup table
state = s.inv_s_box(state + 1);
% AddRoundKey keyexp(1:4)
state = bitxor(state, (s.keyexp(1:4, :))');
out = state;

测试文件

[file path]=uigetfile('*.*','Select the Input Image');
Img=imread([path file]);
keyh= {'2b' '7e' '15' '16' '28' 'ae' 'd2' 'a6'...
    'ab' 'f7' '15' '88' '09' 'cf' '4f' '3c'};
key = hex2dec(keyh);

s = aesinit(key);
[n m h]=size(Img);
R=Img(:,:,1);
G = Img(:,:,2);
B = Img(:,:,3);
R=double(R);
G=double(G);
B=double(B);
x=length(R);

ivh = {'00' '01' '02' '03' '04' '05' '06' '07'...
    '08' '09' '0a' '0b' '0c' '0d' '0e' '0f'};
iv = hex2dec(ivh);

s = aesinit(key);
mode= input('entrer le choix:')
switch lower(mode)
    case {'decrypt', 'dec', 'd'}


mode = input('entrer le mode:')
switch lower(mode)
    case {'ecb'}

image_decrypt_R = aes(s, 'dec', 'ecb', R);
image_decrypt_G = aes(s, 'dec', 'ecb', G);
image_decrypt_B = aes(s, 'dec', 'ecb', B);
    case {'cbc'}

image_decrypt_R = aes(s, 'dec', 'cbc', R, iv);
image_decrypt_G = aes(s, 'dec', 'cbc', G , iv);
image_decrypt_B = aes(s, 'dec', 'cbc', B , iv);
    case {'cfb'}
sbit= input('entrer 0<sbit<128 ')

image_decrypt_R = aes(s, 'dec', 'cfb', R, iv, sbit);
image_decrypt_G = aes(s, 'dec', 'cfb', G, iv, sbit);
image_decrypt_B = aes(s, 'dec', 'cfb', B, iv, sbit);  
    case {'ofb'}

image_decrypt_R = aes(s, 'dec', 'ofb', R , iv);
image_decrypt_G = aes(s, 'dec', 'ofb', G , iv);
image_decrypt_B = aes(s, 'dec', 'ofb', B , iv);
    otherwise
        error( 'bad''oper''parameter.');

end

image_decrypt = cat(3,image_decrypt_R, image_decrypt_G, image_decrypt_B);


Image = image_decrypt;

imwrite(Image, 'image_decryptée.jpg');


    case {'encrypt', 'enc', 'e'}


mode = input('entrer le mode:')

switch lower(mode)

    case {'ecb'}

image_crypt_R = aes(s, 'enc', 'ecb', R);
image_crypt_G = aes(s, 'enc', 'ecb', G);
image_crypt_B = aes(s, 'enc', 'ecb', B);
    case {'cbc'}

image_crypt_R = aes(s, 'enc', 'cbc', R, iv);
image_crypt_G = aes(s, 'enc', 'cbc', G , iv);
image_crypt_B = aes(s, 'enc', 'cbc', B , iv);
    case {'cfb'}
sbit= input('entrer 0<sbit<128 ')

image_crypt_R = aes(s, 'enc', 'cfb', R, iv, sbit);
image_crypt_G = aes(s, 'enc', 'cfb', G, iv, sbit);
image_crypt_B = aes(s, 'enc', 'cfb', B, iv, sbit);  
    case {'ofb'}

image_crypt_R = aes(s, 'enc', 'ofb', R , iv);
image_crypt_G = aes(s, 'enc', 'ofb', G , iv);
image_crypt_B = aes(s, 'enc', 'ofb', B , iv);
    otherwise
        error( 'bad''oper''parameter.');

end

        image_crypt = cat(3,image_crypt_R, image_crypt_G, image_crypt_B);


Image = image_crypt;



imwrite(Image, 'image_cryptée.jpg');

    otherwise
        error('Bad ''oper'' parameter.');
end

Answer 1

您正在将加密图像写入JPEG文件。 JPEG是一种有损压缩格式，生成的文件不具有与图像中完全相同的像素值。

这种差异通常很小并且对人眼不显眼。但加密的本质是，密文的微小差别可能意味着明文的完全加扰。

所以，你拍摄你的形象;你使用AES加密它的像素值（OK到目前为止）;你把它写成JPEG图像;你读回来了 - 现在像素值已经改变了。你使用AES解密它的像素值，你得到废话 - 因为你解密的密文不是AES加密的结果，它是AES加密加上错误的结果由JPEG压缩引入。

图像解密看起来像使用AES的加密图像

1 个答案: