Plaintext + Cipher

Question

This is a continuing from previous forum that has been removed for no reason why! - I just don't understand that all the thread seems disappear. I think something wrong with the setting anyhow here is the latest one: Vulpes, I think for now we use the C sharpe version with these Keys and cipher text.

The code still in testing so will see what went wrong on here. Thanks.

PS: Could it be that the text is encoded with padding?

using System;
using System.Security.Cryptography;
using System.Text;
using System.IO;

class Program
{
static void Main()
{
Encoding ascii = Encoding.ASCII;
byte[] key = {0x9b, 0x4c, 0x3d, 0x50, 0x3b, 0x00, 0x00, 0x00}; // use null bytes initially
byte[] cipherText2 = {0x2e, 0x4c, 0x56, 0xe7, 0xf9, 0xf9, 0xd0, 0xef,
0xab, 0x3c, 0x4d, 0x2e, 0x2f, 0x21, 0xf5, 0xcd,
0x8e, 0x9e, 0xd0, 0xf8, 0xe7, 0xa8, 0xd0, 0xbc};
byte[] cipherText = null;
byte[] plainText = null;
string s = null;
bool isCandidate = false;
StreamWriter sw = new StreamWriter("candidates.txt");
for(int i = 0; i < 255; i += 2)
{
for(int j = 0; j < 255; j += 2)
{
for(int k = 0; k < 255; k += 2)
{
key[5] = (byte)i;
key[6] = (byte)j;
key[7] = (byte)k;
cipherText = DesDecrypt(cipherText2, key);
plainText = DesDecrypt(cipherText, key);
s = ascii.GetString(plainText);
isCandidate = true;
foreach(char c in s)
{
int ascval = (int)c;
if (ascval == 63 || ascval < 32 || ascval > 126)
{
isCandidate = false;
break;
}
}
if (isCandidate)
{
string result = String.Format("{0} : {1} : {2} - {3}", i, j, k, s); // now includes bytes
Console.WriteLine(result); // now writes candidate to console as well
sw.WriteLine(result);
}
}
}
Console.WriteLine("i = {0} completed", i); // indication of where we're at
}
sw.Close();
}

static byte[] DesEncrypt(byte[] plainText, byte[] key)
{
// Create a new DES key.
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
// Set the KeySize = 64 for 56-bit DES encryption.
// The msb of each byte is a parity bit, so the key length is actually 56 bits.
des.KeySize = 64;
des.Key = key;
des.Mode = CipherMode.ECB;
des.Padding = PaddingMode.None;

ICryptoTransform ic = des.CreateEncryptor();

byte[] enc = ic.TransformFinalBlock(plainText, 0, 24); // 24 bytes assumed

return enc;
}

static byte[] DesDecrypt(byte[] cipherText, byte[] key)
{
DESCryptoServiceProvider des = new DESCryptoServiceProvider();

des.KeySize = 64;
des.Key = key;
des.Mode = CipherMode.ECB;
des.Padding = PaddingMode.None;

ICryptoTransform ic = des.CreateDecryptor();

byte[] dec = ic.TransformFinalBlock(cipherText, 0, 24);

return dec;
}

}

Vulpes · Answer

The classic example of the difference between call by value and call by reference is a swap function. Consider this code: void swap1(int x int y) { int temp; temp = x; x = y; y = temp; } void swap2(int *x int *y) { int temp; temp = *x; *x = *y; *y = temp; } // within some other function int x = 1; int y = 2; swap1(x y); cout swap2(&x &y); cout When function swap1 is called the arguments are passed by value which means that the values of the local variables x and y are copied into the parameters of the same name. When this function executes the values of the parameters x and y are exchanged within the function. However when the function returns the local variables x and y still have the values they did to start with. This is because it's only copies of their values which have been swapped not the original values. When function swap2 is called the arguments are passed by reference which means that the addresses of the local variables x and y are passed to parameters of the same name. This means in effect that the parameters share the same memory addresses as the local variables. When this function executes the values of the parameters x and y are exchanged within the function as before. However when the function returns the local variables x and y have also had their values swapped. This is because the parameters were sharing the same memory addresses as these variables which therefore exchanged the values of the variables themselves.

Vulpes · Answer

One of the things I've always disliked about Java is that arguments are always passed by value (in the sense used by C#). This means that you can't write a method to swap basic types unless you wrap them in a reference type first. When you pass a reference type (i.e. a reference to an object) by value then its the reference that gets copied. Consequently the method does have access to the original object and so can alter its state.

Sam Hobbs · Answer

I will give you my answer that I was going to give before Vulpes's so in other words this is independent of what he said. It depends on the language. The simplified answer is that a call by reference passes an object so that it can be modified; in other words a reference to the object is passed so the actual object can be accessed. A call by value passes the value; in other words a copy of the data so that the data in the calling function is not modified. The terms are meaningful in a language such as VB 6 and I assume for VB .Net too. The terms are so confusing for the C language that I think it is foolish to use the terms for C. I would have said that regardless of what Vulpes said. In C an address can be passed and therefore it is confusing whether that is a call by reference or a call by value. Certainly we dcan try to define what is what but I think it is best to not even try for C. In C++ there is the reference operator and such; I am not sure of the terminology. In C++ a reference is a new syntax for pointers but they are usually not described as pointers and C++ references are much safer than pointers. A reference in C++ is confusing because they are used everywhere in a program not just for function calls. Similarly C# defines all classes as a reference type and C# has the ref keyword. All that is still confusing a bit for me; I suppose that ref in a function prototype is needed only for value types but all that is one thing that can be very confusing for those of us learning C#. So my advice is to not use the terms by reference and by value for C C++ and C# unless you are describing use of the ref keyword in C#. I am not sure about Java except that I assume the terms are equally confusing/meaningless for Java too. When the terms are used the important distinction is that by value means that the called function cannot change the data that the calling function has but by reference means that it can.

Vulpes · Answer

This is what you should have entered: Please enter number of rows in matrix: 2 Please enter number of columns in matrix and rows in vector 3 Enter the 3 columns of row 1 of the matrix 1 2 3 Enter the 3 columns of row 2 of the matrix 4 5 6 Enter the 3 rows of the vector 5 6 7 The result is a vector with 2 rows as follows 38 92 Notice that the first element of the result vector should be 38 rather than 35: 1 x 5 + 2 x 6 + 3 x 7 = 38

Vulpes · Answer

You should really have started a new thread for this question (in the Visual C++ category) as it's a totally different question to the one asked originally on this thread. However in view of the problems we've had 'losing' threads I'm prepared to answer it on here :) As arrays in C++ need to be fixed size at compile time the only thing you can do is to define the dimensions of the array to be big enough to accommodate the maximum matrix and vector sizes the user is likely to want to use. If that's 10 by 10 say then I'd define MAX_SIZE to be 10. The following program should do what you want: #include stdafx.h #include #include #define MAX_SIZE 10 using namespace std; int main() { int mat[MAX_SIZE][MAX_SIZE]; int vec[MAX_SIZE]; int result[MAX_SIZE]; int rowscols ij; cout cin>>rows; cout cin>>cols; for(i = 0; i { cout for(j = 0; j >mat[i][j]; } cout for(i = 0; i >vec[i]; for(i = 0; i { result[i] = 0; for(j = 0; j { result[i] += mat[i][j] * vec[j]; } } cout for(i = 0; i return 0; }

Vulpes · Answer

Limiting the string length to 8 bytes actually makes some sense as DES has a block size of 64 bits. Having said that the first thing I did was to test the algorithm on plaintext which was 24 bytes long and it double encrypted and decrypted fine. But no matter if it's working go with it :)

Vulpes · Answer

C# is more like Java than C++ though they're all members of the C family of languages and so a large part of their syntax is similar. The C# and Java compilers produce an intermediate or byte code which is then converted 'on the fly' to native code by the CLR or JVM respectively. In contrast C++ compiles directly to native code and so tends to execute more quickly than the other two. However it is a much more complex language and so programs usually take longer to develop.

Vulpes · Answer

OK annotated code as follows: try { // creates a SecretKeyFactory object to convert keys for DES into key specifications kf = SecretKeyFactory.getInstance(DES); // creates a cipher object for DES using ECB and no padding cf = Cipher.getInstance(DES/ECB/NoPadding); } ... ... // i j k represent the 3 bytes to be filled in the key // we're ignoring the odd numbers and so each loop runs through the values 0 2 4 ... 254 for(int i = 0; i { for(int j = 0; j { for(int k = 0; k { .. .. try { ks = new DESKeySpec(key); // creates a DES key spec object using the current key ky = kf.generateSecret(ks); // Generates a SecretKey object from the key spec cf.init(Cipher.DECRYPT_MODE ky); // initializes cipher for decryption using the secret key cipherText = cf.doFinal(cipherText2); // decrypts cipherText and assigns result to same variable plainText = cf.doFinal(cipherText); // decrypts new value of ciphertext and assigns result to plainText } catch(Exception e) // catches any errors prints out message and terminates program { System.out.println(e.getMessage()); return; } .. .. s = new String(plainText US-ASCII); // creates an ASCII string 's' from plainText isCandidate = true; // sets isCandidate to true for(int m = 0; m .. .. { char c = s.charAt(m); // gets the char at index 'm' (zero based) // if 'c' is anything other than a letter or numeral if (!((c >= '0' && c = 'A' && c = 'a' && c { isCandidate = false; // it's not a candidate break; // no point going on with the loop } } .. .. if (isCandidate) // if the string is a candidate { // create a formatted string - replace the placeholders %d (integers) or %s (strings) // with the variables i j  k and s respectively String result = String.format(%d : %d : %d - %s i j k s); System.out.println(result); // just writes results to console now }

Vulpes · Answer

I've asked Mahesh to look into why the previous threads have been deleted. I'm surprised you're sticking with the C# code when the Java code was executing far more quickly. I've tried to optimize the former below to run a bit quicker but it's still 'dog slow': using System; using System.Security.Cryptography; using System.Text; using System.IO; class Program { static DESCryptoServiceProvider des; static void Main() { // Create a new DES key. des = new DESCryptoServiceProvider(); // Set the KeySize = 64 for 56-bit DES encryption. // The msb of each byte is a parity bit so the key length is actually 56 bits. des.KeySize = 64; des.Mode = CipherMode.ECB; des.Padding = PaddingMode.None; Encoding ascii = Encoding.ASCII; byte[] key = {0x9b 0x4c 0x3d 0x50 0x3b 0x00 0x00 0x00}; // use null bytes initially byte[] cipherText2 = {0x2e 0x4c 0x56 0xe7 0xf9 0xf9 0xd0 0xef 0xab 0x3c 0x4d 0x2e 0x2f 0x21 0xf5 0xcd 0x8e 0x9e 0xd0 0xf8 0xe7 0xa8 0xd0 0xbc}; byte[] cipherText = null; byte[] plainText = null; string s = null; bool isCandidate = false; for(int i = 0; i { for(int j = 0; j { for(int k = 0; k { key[5] = (byte)i; key[6] = (byte)j; key[7] = (byte)k; cipherText = DesDecrypt(cipherText2 key); plainText = DesDecrypt(cipherText key); s = ascii.GetString(plainText); isCandidate = true; foreach(char c in s) { if (!((c >= '0' && c = 'A' && c = 'a' && c { isCandidate = false; break; } } if (isCandidate) { string result = String.Format({0} : {1} : {2} - {3} i j k s); // now includes bytes Console.WriteLine(result); // now writes candidate to console rather than file } } } Console.WriteLine(i = {0} completed i); // indication of where we're at } } static byte[] DesEncrypt(byte[] plainText byte[] key) { des.Key = key; ICryptoTransform ice = des.CreateEncryptor(); byte[] enc = ice.TransformFinalBlock(plainText 0 24); // 24 bytes assumed return enc; } static byte[] DesDecrypt(byte[] cipherText byte[] key) { des.Key = key; ICryptoTransform icd = des.CreateDecryptor(); byte[] dec = icd.TransformFinalBlock(cipherText 0 24); return dec; } } If you look at this link ( http://msdn.microsoft.com/en-us/library/system.security.cryptography.paddingmode.aspx ) there are five possible padding modes including 'None' which you can try in turn. Just change the line: des.Padding = PaddingMode.None; to: des.Padding = PaddingMode.PKCS7; and so on for the others.

Sam Hobbs · Answer

As for using a string's length or using the constant 8 if it were me I would use the debugger to see what is in the length. If the number 8 works yet the length does not then I sure would want to know what the length is and why it is not the value that it should be. You could add a line that is temporary for diagnostic purposes that would write a line to the debugging log showing what the length is when it is not 8.

Sam Hobbs · Answer

If a question is definitely about C++ then please ask in the C++ forum. Especially if it is about the language. There are many questions in the C# Language forum that should not be; they should be put in one of the other forums that are appropriate for the question. If a question is about use of .Net but the language is C++ then it is not definite where it should be. So try to do what you should do and I hope everyone will have respect and appreciation for your efforts. In otehr forusm there would be separate forums for C++ and for other topics that are not about the language but is about programs written in C++. The CodeGuru.com forums is an example of that. Since the C# Corner web site (this one) gets so few C++ questions it is reasonable for C++ questions to be put in the C++ forum. If however the question is much more a question of Security & Cryptography using .Net then it seems appropriate to put the question here. Hopefully you will get good at converting code between C++ and C#.

siabanie banie · Answer

I have been doing some exercise to get use of the C++ language I wonder if I can post it here or shall I use the C++ forum? As I can see that room isn't much as active as this Please suggest thanks. -TMiB

siabanie banie · Answer

Thanks for the inputs Sam and Vulpes In regards to the 8 lenght I cannot answer why it is working but I can see what you trying to point out. But I think Vulpes and I had tried to see the posiblities for this issue and as at the moment it seems working I think it is okay. But if it rises an issue I certainly will let you guys know Thanks agian for the explanantion about the call by value and reference. As I am very new in C++ and have very basic knowledge in Java it is difficult for me to follow all this up - Sometimes I mix them together and confused myself lol.

Sam Hobbs · Answer

As for the difference between: for(int m = 0; m and for(int m = 0; m I don't even know where to look for Java language documentation. If the length method of the Java String class does not always return 8 for the data and if exactly 8 bytes needs to be processed in that situation then of course there is a difference. In C the string length (strlen) is determined by the first character with the value zero. The C++ std::string class determines the length in a more meaningful manner. If the code is supposed to process exactly 8 bytes and the code that uses the length property does not work then I certainly would investigate what determines the length.

Sam Hobbs · Answer

And as I have said the terminology can be confusing. In Microsoft Visual C++ there is something called MFC for doing Windows programming using C++. The MFC documentation often says that a parameter cannot be modified but that is confusing since it is only the address that cannot be modified; the object at that address can be modified. They could have used more precise terminology but they do not. Your description of Java sounds similar to MFC. It would help for people learning Java to understand that. I will try to remember it.

siabanie banie · Answer

Thanks for the answer Sam and Vulpes Yes what I am trying to do is create separate for a Matrix and Vector - I just want to see how these two classes can be call. One question I may ask: Can you give me very easy example the different between call by references and call by value? I have seen some example online but I still not get it and understand what the different. I will try to implement the way I did above see if I can make it more 'understand' at least for me. Thanks.

Vulpes · Answer

Sam's post reminded me that I'd forgotten to answer these further questions :) It's not very active but there is in fact a Visual C++ forum on this site: http://www.c-sharpcorner.com/Forums/Post/31/visual-c.aspx I've heard of web spider which is 'web crawler' software but I don't use it or know much about it. I suppose you could create separate classes for a Matrix and a Vector or you could regard the latter as a special case of the former where the number of columns was one. You'd then need to define a method of this class which did matrix multiplication. Is that what you have in mind?

Sam Hobbs · Answer

In answer to the question of  if you know about C sharp then you be able to do Java and C too?  the C++ language includes the C++ standard library and that is very different from C#. I am not familiar enough with Java enough to know if its libraries are more like C++ or C# or if they are also quite different from the others. So eventhough the syntax of all three languages are nearly identical there are substantial differences in the libraries. C# uses .Net (technically it is CLI) and the other two do not. Also note that C has a runtime library that is part of the language and the C++ standard library does many of the things that the C runtime does but not everything. So at that level C and C++ vary in the manner that if you use C++ you tend to do things the C++ way that cannot be done using C. For most things the difference in performance that can be acheived by all three is usually not considered to be significant and the portability of C# and Java usually is a significant consideration. When performance is critical and portability is not a concern C++ is considered a better choice than C# and Java.

siabanie banie · Answer

Hi Vulpes Thanks again for the helped - But I wonder if I could do the above code as like this example shown below. I am using visual studio and new about this language and IDE so I like to see how we can implement it in this way? Is it feasible or does it make it difficult to see? object.cpp #include iostream > using namespace std; #include  circle.hh  main() { cout double r; cin >> r; CircleC circle(r); // construct a circle radius r cout circle.Area () cout circle.Circum () } circle.hh // C++ header file for CircleC class CircleC { public: CircleC (double radius); // Constructor for CircleC double Circum();// Member function - circumference double Area(); // member function - area private: double radius;// private data cannot be accessed outside }; circle.cpp // C++ implementation #include  circle.hh  CircleC::CircleC (double r) : radius(r) {} double CircleC::Circum () { return 2.0*3.14159*radius;} double CircleC::Area () { return 3.14159*radius*radius;}

siabanie banie · Answer

Thanks Vulpes yes do while will def do the job - I was thinkin about while loop but I think while loop will ignore the first statement if it is not true. Thanks for the helped! Question; where can I ask question for C++ as this is for C# as I can't see C++ thread/forum in here? Any recommendation? And do you know anything about web spider?

Vulpes · Answer

Yes you need to place the code (except the declarations) in a loop. I've used a do/while loop below: #include stdafx.h #include #include #define MAX_SIZE 10 using namespace std; int main() { int mat[MAX_SIZE][MAX_SIZE]; int vec[MAX_SIZE]; int result[MAX_SIZE]; int rowscols ij; char yn; do { cout cin>>rows; cout cin>>cols; for(i = 0; i { cout for(j = 0; j >mat[i][j]; } cout for(i = 0; i >vec[i]; for(i = 0; i { result[i] = 0; for(j = 0; j { result[i] += mat[i][j] * vec[j]; } } cout for(i = 0; i do { cout cin>>yn; } while (yn != 'Y' && yn != 'y' && yn != 'N' && yn !='n'); // keep asking till get a valid answer } while(yn == 'Y' || yn == 'y'); return 0; }

siabanie banie · Answer

Yes you were right my mistake - Thanks very much :) If I want to say: Ask the user to try again without exit immediately? How can I do that? Do I have to do another loops? I mean once user placing all the matrix; it will print Do you want to try again Press Y or N will Exit the console. Then if user press Y it will go repeat all over again. No will exit.

siabanie banie · Answer

Hi Vulpes Yes sorry I should have start new tread but...:) Thanks for the input - I have tried them but it didnt seem give me the output I expected? Or perhaps I typed an incorrect row or columns? As i tried this: e.g (1 2 3) (5) (4 5 6) (6) (7) Which the correct answer will be (35) (92) Edited: Sorry I think I placed a wrong rows and columns - Thanks again yes and work great! Thanks!

siabanie banie · Answer

I wonder if you could give me some assist about this program: I have implement a short program in C++ to multiply a vector by a matix e.g (1 2 3) (5) (4 5 6) (6) (7) Which the correct answer will be (35) (92) The program need so that it is easy to change the size of the matrix and vector. Here what I have done so far but it isn't working as I want. I wonder if would be easy to use const declaraions to specify the dimensions any idea? #include stdafx.h #include #include using namespace std; int main() { int **mat1; int **mat2; int **result; int rowcol; cout cin>>row>>col; mat1 = new int *[row]; mat2 = new int *[row]; result = new int *[row]; int kij; for (k=0; k mat1[k] = new int[col]; mat2[k] = new int[col]; result[k] = new int[col]; for (i=0; i for (j=0; j mat1[k][i] = k + i; for (j=0; j mat2[i][k] = j + k; for(i=0; i result[i][k] += (mat1 [i][k] * mat2[k][j]); cout } PS: if you have a better way and simple way to demo this would be helpful. Thanks.

siabanie banie · Answer

Thanks yes. I can't really think what else we did wrong but as long it works that good. See if it will handle some error soon - but thanks again.

siabanie banie · Answer

I see okay well it's not exaclty working but it seems work in some point... I just changed the :for(int m = 0; m < s.length(); m++) to for(int m = 0; m < 8; m++) and it seems to work? But Im not sure if it is correct or not. But for now I leave it as is.. as I have to move on to different exercise. But thanks for your support and help! Much appreciated!

Vulpes · Answer

Yes C# is my best language nowadays and I'm not bad in C/C++/VB but only fair in Java which I rarely use. BTW have you managed to get it to work now and if so was it the padding that was the problem?

siabanie banie · Answer

Thanks Vulpes So you are much better in C sharp than Java / C++? Cos if you know about C sharp then you be able to do Java and C too?

siabanie banie · Answer

Thanks Vuples that's very helpful! Can I ask one question between C sharp an C++ I assume these two almost the same?

siabanie banie · Answer

Hi Vulpes Back to the Java code do you mind explaining to me few lines of the code what they are actually doing so I can follow them up and maybe tweak them please. Here the snippets of the code: try { kf = SecretKeyFactory.getInstance(DES); cf = Cipher.getInstance(DES/ECB/NoPadding); } ... ... for(int i = 0; i { for(int j = 0; j { for(int k = 0; k { .. .. try { ks = new DESKeySpec(key); ky = kf.generateSecret(ks); cf.init(Cipher.DECRYPT_MODE ky); cipherText = cf.doFinal(cipherText2); plainText = cf.doFinal(cipherText); } catch(Exception e) { System.out.println(e.getMessage()); return; } .. .. s = new String(plainText US-ASCII); isCandidate = true; for(int m = 0; m .. .. { char c = s.charAt(m); if (!((c >= '0' && c = 'A' && c = 'a' && c { isCandidate = false; break; } } .. .. if (isCandidate) { String result = String.format(%d : %d : %d - %s i j k s); System.out.println(result); // just writes results to console now } .. ..