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
答案 0 :(得分：2)
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。