How to Decryption in des algorithms ?

Hello I have an algorithm des code. This code executes the encryption correctly, but does not perform decryption. Please help me with that. code : clc clear tic mydata='C:\Users\digitalhouse\Desktop\DES\mydata.txt'; fid = fopen(mydata, 'r'); M = fread(fid,'*char')' fclose(fid) K = '1256984563214569'; MB=[]; for i=1:16 Mi=M(i); MBi=['0000',dec2bin(hex2dec(Mi))]; MBi=MBi(end-3:end); MBi=[str2num(MBi(1)),str2num(MBi(2)),str2num(MBi(3)),str2num(MBi(4))]; MB=[MB,MBi]; end M=MB ;

KB=[]; for i=1:16 Ki=K(i); KBi=['0000',dec2bin(hex2dec(Ki))]; KBi=KBi(end-3:end); KBi=[str2num(KBi(1)),str2num(KBi(2)),str2num(KBi(3)),str2num(KBi(4))]; KB=[KB,KBi]; end K=KB; E=[32, 1, 2, 3, 4, 5; 4, 5, 6, 7, 8, 9; 8, 9,10,11,12,13; 12,13,14,15,16,17; 16,17,18,19,20,21; 20,21,22,23,24,25; 24,25,26,27,28,29; 28,29,30,31,32,1]; S1=[14, 4, 13, 1, 2, 15, 11, 8, 3, 10, 6, 12, 5, 9, 0, 7; 0, 15, 7, 4, 14, 2, 13, 1, 10, 6, 12, 11, 9, 5, 3, 8; 4, 1, 14, 8, 13, 6, 2, 11, 15, 12, 9, 7, 3, 10, 5, 0; 15, 12, 8, 2, 4, 9, 1, 7, 5, 11, 3, 14, 10, 0, 6, 13]; S2=[15, 1, 8, 14, 6, 11, 3, 4, 9, 7, 2, 13, 12, 0, 5, 10; 3, 13, 4, 7, 15, 2, 8, 14, 12, 0, 1, 10, 6, 9, 11, 5; 0, 14, 7, 11, 10, 4, 13, 1, 5, 8, 12, 6, 9, 3, 2, 15; 13, 8, 10, 1, 3, 15, 4, 2, 11, 6, 7, 12, 0, 5, 14, 9]; S3=[10, 0, 9, 14, 6, 3, 15, 5, 1, 13, 12, 7, 11, 4, 2, 8; 13, 7, 0, 9, 3, 4, 6, 10, 2, 8, 5, 14, 12, 11, 15, 1; 13, 6, 4, 9, 8, 15, 3, 0, 11, 1, 2, 12, 5, 10, 14, 7; 1, 10, 13, 0, 6, 9, 8, 7, 4, 15, 14, 3, 11, 5, 2, 12]; S4=[7, 13, 14, 3, 0, 6, 9, 10, 1, 2, 8, 5, 11, 12, 4, 15; 13, 8, 11, 5, 6, 15, 0, 3, 4, 7, 2, 12, 1, 10, 14, 9; 10, 6, 9, 0, 12, 11, 7, 13, 15, 1, 3, 14, 5, 2, 8, 4; 3, 15, 0, 6, 10, 1, 13, 8, 9, 4, 5, 11, 12, 7, 2, 14]; S5=[2, 12, 4, 1, 7, 10, 11, 6, 8, 5, 3, 15, 13, 0, 14, 9; 14, 11, 2, 12, 4, 7, 13, 1, 5, 0, 15, 10, 3, 9, 8, 6; 4, 2, 1, 11, 10, 13, 7, 8, 15, 9, 12, 5, 6, 3, 0, 14; 11, 8, 12, 7, 1, 14, 2, 13, 6, 15, 0, 9, 10, 4, 5, 3]; S6=[12, 1, 10, 15, 9, 2, 6, 8, 0, 13, 3, 4, 14, 7, 5, 11; 10, 15, 4, 2, 7, 12, 9, 5, 6, 1, 13, 14, 0, 11, 3, 8; 9, 14, 15, 5, 2, 8, 12, 3, 7, 0, 4, 10, 1, 13, 11, 6; 4, 3, 2, 12, 9, 5, 15, 10, 11, 14, 1, 7, 6, 0, 8, 13]; S7=[4, 11, 2, 14, 15, 0, 8, 13, 3, 12, 9, 7, 5, 10, 6, 1; 13, 0, 11, 7, 4, 9, 1, 10, 14, 3, 5, 12, 2, 15, 8, 6; 1, 4, 11, 13, 12, 3, 7, 14, 10, 15, 6, 8, 0, 5, 9, 2; 6, 11, 13, 8, 1, 4, 10, 7, 9, 5, 0, 15, 14, 2, 3, 12]; S8=[13, 2, 8, 4, 6, 15, 11, 1, 10, 9, 3, 14, 5, 0, 12, 7; 1, 15, 13, 8, 10, 3, 7, 4, 12, 5, 6, 11, 0, 14, 9, 2; 7, 11, 4, 1, 9, 12, 14, 2, 0, 6, 10, 13, 15, 3, 5, 8; 2, 1, 14, 7, 4, 10, 8, 13, 15, 12, 9, 0, 3, 5, 6, 11];

P=[16,7,20,21,29,12,28,17,1,15,23,26,5,18,31,10,2,8,24,14,32,27,3,9,19,13,30,6,22,11,4,25];

PC1=[57,49,41,33,25,17,9,1,58,50,42,34,26,18,10,2,59,51,43,35,27,19,11,3,60,52,44,36,63,55,47,39,31,23,15,7,62,54,46,38,30,22,14,6,61,53,45,37,29,21,13,5,28,20,12,4];

PC2=[14,17,11,24,1,5,3,28,15,6,21,10,23,19,12,4,26,8,16,7,27,20,13,2,41,52,31,37,47,55,30,40,51,45,33,48,44,49,39,56,34,53,46,42,50,36,29,32];

Ki=zeros(16,48);

K_PC1=K(PC1); C0=K_PC1(1:28); D0=K_PC1(29:56);

for i=1:16 if i==1||i==2||i==9||i==16 C0=[C0(2:end),C0(1)]; D0=[D0(2:end),D0(1)]; else C0=[C0(3:end),C0(1:2)]; D0=[D0(3:end),D0(1:2)]; end K_LS=[C0,D0];

    Ki(i,:)=K_LS(PC2); 
end

L=M(1:32); R=M(33:64);

for i=1:16 E0=reshape(E',1,48); R_E=R(E0); R_Ki=mod(R_E+Ki(i,:),2);

    B=R_Ki(1:6); 

    x=B(1)*2+B(6)+1;     
    y=B(2)*8+B(3)*4+B(4)*2+B(5)+1; 
    C=['0000',dec2bin(S1(x,y))];   
    C=C(end-3:end); 
    C1=[str2num(C(1)),str2num(C(2)),str2num(C(3)),str2num(C(4))]; 

    B=R_Ki(7:12); 
    x=B(1)*2+B(6)+1; 
    y=B(2)*8+B(3)*4+B(4)*2+B(5)+1; 
    C=['0000',dec2bin(S2(x,y))]; 
    C=C(end-3:end); 
    C2=[str2num(C(1)),str2num(C(2)),str2num(C(3)),str2num(C(4))]; 
        B=R_Ki(13:18); 
    x=B(1)*2+B(6)+1; 
    y=B(2)*8+B(3)*4+B(4)*2+B(5)+1; 
    C=['0000',dec2bin(S3(x,y))]; 
    C=C(end-3:end); 
    C3=[str2num(C(1)),str2num(C(2)),str2num(C(3)),str2num(C(4))]; 

    B=R_Ki(19:24); 
    x=B(1)*2+B(6)+1; 
    y=B(2)*8+B(3)*4+B(4)*2+B(5)+1; 
    C=['0000',dec2bin(S4(x,y))]; 
    C=C(end-3:end); 
    C4=[str2num(C(1)),str2num(C(2)),str2num(C(3)),str2num(C(4))]; 

    B=R_Ki(25:30); 
    x=B(1)*2+B(6)+1; 
    y=B(2)*8+B(3)*4+B(4)*2+B(5)+1; 
    C=['0000',dec2bin(S5(x,y))]; 
    C=C(end-3:end); 
    C5=[str2num(C(1)),str2num(C(2)),str2num(C(3)),str2num(C(4))]; 
        B=R_Ki(31:36); 
    x=B(1)*2+B(6)+1; 
    y=B(2)*8+B(3)*4+B(4)*2+B(5)+1; 
    C=['0000',dec2bin(S6(x,y))]; 
    C=C(end-3:end); 
    C6=[str2num(C(1)),str2num(C(2)),str2num(C(3)),str2num(C(4))]; 

    B=R_Ki(37:42); 
    x=B(1)*2+B(6)+1; 
    y=B(2)*8+B(3)*4+B(4)*2+B(5)+1; 
    C=['0000',dec2bin(S7(x,y))]; 
    C=C(end-3:end); 
    C7=[str2num(C(1)),str2num(C(2)),str2num(C(3)),str2num(C(4))]; 

    B=R_Ki(43:48); 
    x=B(1)*2+B(6)+1; 
    y=B(2)*8+B(3)*4+B(4)*2+B(5)+1; 
    C=['0000',dec2bin(S8(x,y))]; 
    C=C(end-3:end); 
    C8=[str2num(C(1)),str2num(C(2)),str2num(C(3)),str2num(C(4))]; 
    C=[C1,C2,C3,C4,C5,C6,C7,C8]; 

    R_P=C(P); 

    TEMP=L; 
    L=R; 
    R=mod(TEMP+R_P,2); 
end

TEMP=L; L=R; R=TEMP;

C=[L,R]; CS=[]; C=num2str(C); pos=find(C~=' '); C=C(pos); for i=1:4:61 Ci=C(i:i+3); CS=[CS,num2str(dec2hex(bin2dec(Ci)))]; end C=CS mydata1='C:\Users\digitalhouse\Desktop\DES\mydata1.txt'; fid1=fopen(mydata1,'w'); fwrite(fid1,C)

t=toc

[Rik]

I recall that some time ago, someone mentioned that under US law (which governs this site) it is illegal to discuss non-trivial encryption and decryption. That would mean no one can legally help you on this site.

Also, you haven't formatted your code properly. Select your code and click the {}Code button.

[mohamad gholami]

hi What do you think I need to do to solve my problem. If you can,please help me for solve this problem.