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Introduction

RC6 is an evolutionary improvement of RC5, designed to meet the requirements of the Advanced Encryption Standard (AES). Like RC5, RC6 makes essential use of data-dependent rotations. New features of RC6 include the use of four working registers instead of two, and the inclusion of integer multiplication as an additional primitive operation. The use of multiplication greatly increases the diffusion achieved per round, allowing for greater security, fewer rounds, and increased throughput. I found an article about it online and fulfilled the algorithm using C++ for fun. Hope it'd be helpful to some interested people.

Details of RC6

Like RC5, RC6 is a fully parameterized family of encryption algorithms. A version of RC6 is more accurately specified as RC6-w/r/b where the word size is w bits, encryption consists of a nonnegative number of rounds r, and b denotes the length of the encryption key in bytes. Since the AES submission is targeted at w = 32 and r = 20, we shall use RC6 as shorthand to refer to such versions. When any other value of w or r is intended in the text, the parameter values will be specified as RC6-w/r. Of particular relevance to the AES effort will be the versions of RC6 with 16-, 24-, and 32-byte keys. For all variants, RC6-w/r/b operates on units of four w-bit words using the following six basic operations. The base-two logarithm of w will be denoted by lgw.

• a + b: integer addition modulo 2^w
• a - b: integer subtraction modulo 2^w
• a @ b: bitwise exclusive-or of w-bit words
• a * b: integer multiplication modulo 2^w
• a <<< b: rotate the w-bit word a to the left by the amount given by the least significant lgw bits of b
• a >>> b: rotate the w-bit word a to the right by the amount given by the least significant lgw bits of b

Note that in the description of RC6 the term "round" is somewhat analogous to the usual DES-like idea of a round: half of the data is updated by the other half; and the two are then swapped. In RC5, the term "half-round" was used to describe this style of action, and an RC5 round was deemed to consist of two half-rounds. This seems to have become a potential cause of confusion, and so RC6 reverts to using the term "round" in the more established way.

To get the detailed algorithm description of RC6-w/r/b. Please read the article "The RC6 Block Cipher" by Ronald L. Rivest, M.J.B. Robshaw, R. Sidney and, Y.L. Yin.

Details of Code

In my program, I fulfilled RC6-32/16. Since the integer addition, subtraction and multiplication don't exceed 2^32 in my program, I don't let their results modulo 2^32 like the operations described above. Anyway, the encryption and decryption go well.

I wrapped the bits rotation operations in two functions DWORD CHexDoc::LeftRotate(DWORD dwVar, DWORD dwOffset) and DWORD CHexDoc::RightRotate(DWORD dwVar, DWORD dwOffset).

DWORD CHexDoc::LeftRotate(DWORD dwVar, DWORD dwOffset)
{
    DWORD temp1, temp2;

    temp1 = dwVar >> (W - dwOffset);
    temp2 = dwVar << dwOffset;
    temp2 = temp2 | temp1;

    return temp2;
}

DWORD CHexDoc::RightRotate(DWORD dwVar, DWORD dwOffset)
{
    DWORD temp1, temp2;

    temp1 = dwVar << (W - dwOffset);
    temp2 = dwVar >> dwOffset;
    temp2 = temp2 | temp1;

    return temp2;
}

The key generation part is like

void CHexDoc::KeyGen(DWORD dwKey)
{
    DWORD P32 = 0xB7E15163;
    DWORD Q32 = 0x9E3779B9;
    DWORD i, A, B;
    DWORD dwByteOne, dwByteTwo, dwByteThree, dwByteFour;

    dwByteOne = dwKey >> 24;
    dwByteTwo = dwKey >> 8;
    dwByteTwo = dwByteTwo & 0x0010;
    dwByteThree = dwKey << 8;
    dwByteThree = dwByteThree & 0x0100;
    dwByteFour = dwKey << 24;

    dwKey = dwByteOne | dwByteTwo | dwByteThree
        | dwByteFour;

    m_dwS[0] = P32;

    for(i = 1; i < 2 * R + 4; i++)
        m_dwS[i] = m_dwS[i - 1] + Q32;

    i = A = B = 0;

    int v = 3 * max(1, 2 * R + 4);

    for(int s = 1; s <= v; s++)
    {
        A = m_dwS[i] = LeftRotate(m_dwS[i] + A + B, 
            OffsetAmount(3));
        B = dwKey = LeftRotate(dwKey + A + B, 
            OffsetAmount(A + B));

        i = (i + 1) % (2 * R + 4);
    }
}

Finally, the core parts of encryption and decryption are as following:

// encrypt the file

void CHexDoc::EncodeFile()
{
    DWORD* pdwTemp;

    for(UINT i = 0; i < m_nDocLength; i += 16)
    {
        pdwTemp = (DWORD*)&m_pFileData[i];

        pdwTemp[0] = (pdwTemp[0] - m_dwS[2 * R + 2]);
        pdwTemp[2] = (pdwTemp[2] - m_dwS[2 * R + 3]);

        for(int j = R; j >= 1; j--)
        {
            DWORD temp = pdwTemp[3];
            pdwTemp[3] = pdwTemp[2];
            pdwTemp[2] = pdwTemp[1];
            pdwTemp[1] = pdwTemp[0];
            pdwTemp[0] = temp;

            DWORD t = 
                LeftRotate((pdwTemp[1] * (2 * pdwTemp[1] + 1)),
                OffsetAmount((DWORD)(log((double)W)/log(2.0))));
            DWORD u = 
                LeftRotate((pdwTemp[3] * (2 * pdwTemp[3] + 1)),
                OffsetAmount((DWORD)(log((double)W)/log(2.0))));
            pdwTemp[0] =
                (RightRotate((pdwTemp[0] - m_dwS[2 * j]),
                OffsetAmount(u))) ^ t;
            pdwTemp[2] = 
                (RightRotate((pdwTemp[2] - m_dwS[2 * j + 1]),
                OffsetAmount(t))) ^ u;
        }

        pdwTemp[1] = (pdwTemp[1] - m_dwS[0]);
        pdwTemp[3] = (pdwTemp[3] - m_dwS[1]);
    }
    pdwTemp = NULL;
    SetModifiedFlag(TRUE);

    POSITION pos = GetFirstViewPosition();
    while(pos != NULL)
    {
        CView* pView = GetNextView(pos);
        pView->RedrawWindow();
    }
}

// decrypt the file

void CHexDoc::DecodeFile()
{
    DWORD* pdwTemp;

    for(UINT i = 0; i < m_nDocLength; i += 16)
    {
        pdwTemp = (DWORD*)&m_pFileData[i];

        pdwTemp[1] = (pdwTemp[1] + m_dwS[0]);
        pdwTemp[3] = (pdwTemp[3] + m_dwS[1]);

        for(int j = 1; j <= R; j++)
        {
            DWORD t = 
                LeftRotate((pdwTemp[1] * (2 * pdwTemp[1] + 1)),
                OffsetAmount((DWORD)(log((double)W)/log(2.0))));
            DWORD u = 
                LeftRotate((pdwTemp[3] * (2 * pdwTemp[3] + 1)),
                OffsetAmount((DWORD)(log((double)W)/log(2.0))));
            pdwTemp[0] = 
                (LeftRotate(pdwTemp[0] ^ t, OffsetAmount(u)) +
                m_dwS[2 * j]);
            pdwTemp[2] = 
                (LeftRotate(pdwTemp[2] ^ u, OffsetAmount(t)) +
                m_dwS[2 * j + 1]);

            DWORD temp = pdwTemp[0];
            pdwTemp[0] = pdwTemp[1];
            pdwTemp[1] = pdwTemp[2];
            pdwTemp[2] = pdwTemp[3];
            pdwTemp[3] = temp;
        }

        pdwTemp[0] = (pdwTemp[0] + m_dwS[2 * R + 2]);
        pdwTemp[2] = (pdwTemp[2] + m_dwS[2 * R + 3]);
    }
    pdwTemp = NULL;
    SetModifiedFlag(TRUE);

    POSITION pos = GetFirstViewPosition();
    while(pos != NULL)
    {
        CView* pView = GetNextView(pos);
        pView->RedrawWindow();
    }
}

Conclusion

In the view window, I showed the Hex and Char content of the loaded file and their addresses. You can see the changes every time you encrypt/decrypt it. Thanks!

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rc6 in jar endra hermawan 23:55 27 May '09   help me please..anyone have source code "encryption sms rc6 in java (j2me)" please send to me dexendra_sinting666@yahoo.co.id thanksss!!!! Sign In·View Thread·PermaLink The bug with overrun mircea131313 2:24 25 Apr '09   I've compiled the code in VS 2005. but if i try to encrypt a file whose length does not devide by 16 (DWORD) i canot decrypt it back. this bug was mentioned in an previous post: Load a short file with text which has a length not divisible by 16; debug using [View menu][debug windows][Memory] window to watch the buffer pdwTemp[0] in the CHexDoc::EncodeFile() function: Set the window once you've stepped over this line: pdwTemp = (DWORD*)&m_pFileData[i]; Then Step Out Of the function and watch as the code writes onto the FDFDFDFD marking the end of the buffer which belong to the system... This is a consequence of the 4-DWORD-at-a-time access: for(UINT i = 0; i < m_nDocLength; i += 16) so you must make sure that the data you're encrypting is in a buffer with an extra 16 Bytes of 'space' after it to avoid overwriting memory. Just how you implement this will depend on the application: memcpy or CString::GetBufferSetLength(...) may be useful. regards Has anyone solved this ? Thank you! Sign In·View Thread·PermaLink is there a rc6 algorithm in vb.net moonshaddow 16:35 30 Oct '08   i looked on the net and could not find anything J.Hardy Sign In·View Thread·PermaLink 1.00/5 Hep block error... Roel Virgel L. Baldon 0:28 7 Oct '08   I have encountered a heap block error pointing to dbgheap.c _CrtIsMemoryBlock function. I noticed that this only happened if the file is around 240KB or more. Is this one of the limit of the application? If not, can somebody please help me fix this error. Sign In·View Thread·PermaLink I have a errors, help me [modified] Srgteam 15:58 22 Nov '07   Hello to all, I dowbload the source code of this project and opened im Visual Studio 2005, then i converted this project. (Visual Studio asked me) And when i start compiling i see one error: In function CHexView::FormatLine hexenc_src\hexencview.cpp(182) : error C2679: binary '+=' : no operator found which takes a right-hand operand of type 'BYTE [17]' (or there is no acceptable conversion) Tell me please, what need to do? Sorry for my English Sign In·View Thread·PermaLink Pls Help~~; ofuka 23:07 14 Mar '06   Im doing my FYP for the final year..My supervisor had asked me to include the encryption for the password that contained inside a text file..... I had downloaded this source code and run it..but it shows me two errors..i don't know what's wrong with the code..... below was the error that was pointed to.... typedef UINT_PTR KSPIN_LOCK; ofuka Sign In·View Thread·PermaLink 1.20/5 DES cryptanalysis with 6 rounds nasor 0:14 7 May '05   Is there any body that has a code in C++ for differential attack on reduced DES to 6 rounds? If you have, please send me a copy of it, if possible for you. Thanks a lot in advance. Regards, Nasoor salame man be to yare ghadimi Sign In·View Thread·PermaLink 2.00/5 RC3, RC4, RC5, RC6 Mansureh Shahraki 7:00 3 Feb '05   Dear all, I am looking for good and complete tutorials about these cryptography algorithms: RC3, RC4, RC5, RC6. Would you please help me? Mansureh (shahraki@rediffmail.com) Sign In·View Thread·PermaLink 1.33/5 Re: RC3, RC4, RC5, RC6 Mingming Lu 7:14 3 Feb '05   you may wanna check out the book "Applied Cryptography, Second Edition: Protocols, Algorthms, and Source Code in C" by Bruce Schneier. It has the exhausted descriptions of many cryptography algorithms. BTW, google is another good way to meet your needs. IS THERE ANYBODY OUT THERE? Sign In·View Thread·PermaLink 3.50/5 Please help me ? lonelywind1982 22:47 18 Mar '04   I wrote again this code to Visual C# but my program only Encode, DeEncode is true with length of file mod 16 =0; This is my code, please help me. private void EncodeFile(string fileRead,string fileWrite) { FileStream sourceStream = new FileStream(fileRead, FileMode.Open, FileAccess.Read); FileStream destinationStream = new FileStream(fileWrite, FileMode.Create, FileAccess.Write); long TotalLen=sourceStream.Length; int Len; long rdLen=0; int count=0; byte[] bufferStream = new byte[4096] ; UInt32[] Data=new UInt32[4]; byte[] buffer=new byte[16]; while(rdLen"<"TotalLen) { Len=sourceStream.Read(bufferStream,0,4096); for(int i = 0; i < Len; i += 16) { Data[0]=BitConverter.ToUInt32(bufferStream,i+0); Data[1]=BitConverter.ToUInt32(bufferStream,i+4); Data[2]=BitConverter.ToUInt32(bufferStream,i+8); Data[3]=BitConverter.ToUInt32(bufferStream,i+12); Data[1]=(Data[1]+m_dwS[0]); Data[3]=(Data[3]+m_dwS[1]); for(int j = 1; j <= R; j++) { UInt32 t = LeftRotate((Data[1] * (2 * Data[1] + 1)), OffsetAmount((UInt32)(Math.Log((double)W)/Math.Log(2.0)))); UInt32 u = LeftRotate((Data[3] * (2 * Data[3] + 1)), OffsetAmount((UInt32)(Math.Log((double)W)/Math.Log(2.0)))); Data[0] = (LeftRotate(Data[0] ^ t, OffsetAmount(u)) + m_dwS[2 * j]); Data[2] = (LeftRotate(Data[2] ^ u, OffsetAmount(t)) + m_dwS[2 * j + 1]); UInt32 temp = Data[0]; Data[0] = Data[1]; Data[1] = Data[2]; Data[2] = Data[3]; Data[3] = temp; } Data[0] = (Data[0] + m_dwS[2 * R + 2]); Data[2] = (Data[2] + m_dwS[2 * R + 3]); count=0; for(int index=0;index<16;index+=4) { buffer[index]=(byte)((Data[count]&0x000000FF)>>0); buffer[index+1]=(byte)((Data[count]&0x0000FF00)>>8); buffer[index+2]=(byte)((Data[count]&0x00FF0000)>>16); buffer[index+3]=(byte)((Data[count]&0xFF000000)>>24); count++; } Array.Copy(buffer,0,bufferStream,i,buffer.Length); } destinationStream.Write(bufferStream,0,Len); rdLen=rdLen+Len; } } private void DeEncodeFile(string fileRead,string fileWrite) { FileStream sourceStream = new FileStream(fileRead, FileMode.Open, FileAccess.Read); FileStream destinationStream = new FileStream(fileWrite, FileMode.Create, FileAccess.Write); long TotalLen=sourceStream.Length; int Len; long rdLen=0; int count=0; byte[] bufferStream = new byte[4096] ; byte[] buffer=new byte[16]; UInt32[] Data=new UInt32[4]; while(rdLen"<"TotalLen) { Len=sourceStream.Read(bufferStream,0,4096); for(int i = 0; i < Len; i += 16) { Data[0]=BitConverter.ToUInt32(bufferStream,i+0); Data[1]=BitConverter.ToUInt32(bufferStream,i+4); Data[2]=BitConverter.ToUInt32(bufferStream,i+8); Data[3]=BitConverter.ToUInt32(bufferStream,i+12); Data[0]=(Data[0]-m_dwS[2*R+2]); Data[2]=(Data[2]-m_dwS[2*R+3]); for(int j = R; j >=1; j--) { UInt32 temp = Data[3]; Data[3]=Data[2]; Data[2]=Data[1]; Data[1]=Data[0]; Data[0]=temp; UInt32 t = LeftRotate((Data[1] * (2 * Data[1] + 1)), OffsetAmount((UInt32)(Math.Log((double)W)/Math.Log(2.0)))); UInt32 u = LeftRotate((Data[3] * (2 * Data[3] + 1)), OffsetAmount((UInt32)(Math.Log((double)W)/Math.Log(2.0)))); Data[0]=(RightRotate((Data[0]-m_dwS[2*j]),OffsetAmount(u)))^t; Data[2]=(RightRotate((Data[2]-m_dwS[2*j+1]),OffsetAmount(t)))^u; } Data[1]=(Data[1]-m_dwS[0]); Data[3]=(Data[3]-m_dwS[1]); count=0; for(int index=0;index<16;index+=4) { buffer[index]=(byte)((Data[count]&0x000000FF)>>0); buffer[index+1]=(byte)((Data[count]&0x0000FF00)>>8); buffer[index+2]=(byte)((Data[count]&0x00FF0000)>>16); buffer[index+3]=(byte)((Data[count]&0xFF000000)>>24); count++; } Array.Copy(buffer,0,bufferStream,i,buffer.Length); } destinationStream.Write(bufferStream,0,Len); rdLen=rdLen+Len; } } private void KeyGen(UInt32 dwKey) { UInt32 P32=0xB7E15163; UInt32 Q32 = 0x9E3779B9; UInt32 i,A, B; UInt32 dwByteOne, dwByteTwo, dwByteThree, dwByteFour; dwByteOne = dwKey >> 24; dwByteTwo = dwKey >> 8; dwByteTwo = dwByteTwo & 0x0010; dwByteThree = dwKey << 8; dwByteThree = dwByteThree & 0x0100; dwByteFour = dwKey << 24; dwKey = dwByteOne | dwByteTwo | dwByteThree | dwByteFour; m_dwS[0] = P32; for(i = 1; i < 2 * R + 4; i++) m_dwS[i] = m_dwS[i - 1] + Q32; A = B =i= 0; int v = 3 * max(1, 2 * R + 4); for(int s = 1; s <= v; s++) { A = m_dwS[i] = LeftRotate(m_dwS[i] + A + B, OffsetAmount(3)); B = dwKey = LeftRotate(dwKey + A + B, OffsetAmount(A + B)); i =( (i + 1) %((UInt32)(2 * R + 4))); } } Sign In·View Thread·PermaLink 2.00/5 How to setup RC6 with C# ? lonelywind1982 1:12 14 Mar '04   I tried to setup RC6 in C# but not easy. Pointer only use in Unsafe mode. The Opperators <<, >> only support int type. Please help me. Thank for read My Message. Sorry for my English because I'm come from VietNam. My email : lonelywind1982@yahoo.com Sign In·View Thread·PermaLink 1.83/5 This program is not run in all Windows OS Brahma 2:33 12 Dec '03   Hi!!! I used this code in my program to encode audio files( *.mp3 files ). I could have successfully decrypt in windows 2000. But problem I am facing is if I am encrypt audio files in win2000 and then trying to decrypt it in Windows XP with the same decrypt functionality, it get crashed. so can you give me suggestion , How I will use this functionality over all the Windows OS. Your help will be highly appreciated. Sign In·View Thread·PermaLink 1.38/5 help me?? xxhimanshu 0:16 5 Nov '03   hi all, i am trying to use as it is the rijndael algorithm..for encrypting and decrypting the xml file...using AES rijndael..32 bit key and block size and also the method is CBC..it adds a few characters at the end of the file which makes it an invalid XML file..while using BLANKs..I am getting the valid XML file..Now i have to do is a server side encryption of the XML files..from php script..so i am using mcrypt library to do the same..but when i use this class to decrypt the same file it says can't secrypt..while i am using the same key and all..there the function is MCRYPT_RIJNDAEL_256..CBC and ECB..but nothing is working..can anyone help me out there in doing the same..or if there is any encryption which works as same in php and vc++ so that i just have to use the function and can do the same..Please help me out..any pointers and ideas are highly appreciated.. Thanks a lot in advance.. Regards, himanshu Sign In·View Thread·PermaLink 5.00/5 weak keys detection krishni 5:22 13 Aug '03   how to detect weak and semi weak keys in the new encryption standards? Sign In·View Thread·PermaLink 2.00/5 Key Length brad_brady 11:43 13 Apr '03   hey, i was just wondering if anyone knew the actual key length used in this program or is it variable?? also if anyone was able to answer the question below on the key gen could you please send it on to me? Life is Tough!!! Sign In·View Thread·PermaLink 1.00/5 key gen abritto 6:48 24 Mar '03   hey, i was wondering how the key generation part of this code worked. when the user inputs a key, what exactly happens? i think the algorithm below is the one used for rc6 but i cant figure out how your code achieves the first part of this, thanks for all your help! Input: User-supplied b byte key preloaded into the c - word array L[0,…,c-1] Number r of rounds Output: w-bit round keys S[0,…,2r + 3] Procedure: S[0]=Pw for i=1 to 2r+3 do S[i]=S[i-1]+Qw A=B=i=j=0 v=3 ? max{c, 2r+4} for s=1 to v do { A=S[i]=(S[i]+A+B)<<E B=L[j]=(L[j]+A+B)<<<(A+B) i=(i+1) mod (2r+4) j=(j+1) mod c } abritto Sign In·View Thread·PermaLink 1.00/5 opening a file abritto 7:42 20 Mar '03   hey, i just wanted to know what exactly we are looking at when we open a file in this application. is it the hex equivalent of the file? also, what are the three columns showing for? Sign In·View Thread·PermaLink 1.00/5 Re: opening a file Mingming Lu 13:07 20 Mar '03   the middle part is the hex equivalent of the file as you said. the left part is the displacement address of the cooresponding data in the middle part. and the right part is the character representation of the file(however, I use '.' to replace some uncommon characters at the right. that's why you can see many '.' over there). Come on! Decode me. Sign In·View Thread·PermaLink vsc++6.0 abritto 4:16 26 Feb '03   when i run this code in visual c++ 6.0 an error keeps coming up that it cannot open the Hexenc.pch file. i opened a new project and copied the code into it, is this the right thing to do? i chose to open a Win32 console application and chose a simple application. i deleted the stdafx files and copied in the ones given. i havent a clue if this was the right thing to do or not?? i'm pretty new to visual c++ and its a bit confusing for me! Thank for your help Sign In·View Thread·PermaLink 2.00/5 Re: vsc++6.0 Mingming Lu 6:53 26 Feb '03   when that happened to me before, I just deleted that .pch file and compiled it again. Then, everything is fine. you can try it. good luck! Come on! Decode me. Sign In·View Thread·PermaLink 2.00/5 can this be changed easily for RC5 abritto 4:43 25 Feb '03   this project looks good and works well, but i was wondering if it would be hard to change the code to use RC5 encryption and decryption. i'm not too good on the programming side of things and any comments or help would be appreciated. Sign In·View Thread·PermaLink 1.00/5 Re: can this be changed easily for RC5 Mingming Lu 5:39 25 Feb '03   I am sorry that I don't try much on RC5. But I believe it shouldn't be hard to change this code to RC5. The framework is the same. I think you just need to replace the core RC6 algorithm to RC5. That shouldn't be painful. Come on! Decode me. Sign In·View Thread·PermaLink 1.00/5 Overrun BossShot 3:18 23 Oct '02   Load a short file with text which has a length not divisible by 16; debug using [View menu][debug windows][Memory] window to watch the buffer pdwTemp[0] in the CHexDoc::EncodeFile() function: Set the window once you've stepped over this line:    pdwTemp = (DWORD*)&m_pFileData[i]; Then Step Out Of the function and watch as the code writes onto the FDFDFDFD marking the end of the buffer which belong to the system... This is a consequence of the 4-DWORD-at-a-time access:    for(UINT i = 0; i < m_nDocLength; i += 16) so you must make sure that the data you're encrypting is in a buffer with an extra 16 Bytes of 'space' after it to avoid overwriting memory. Just how you implement this will depend on the application: memcpy or CString::GetBufferSetLength(...) may be useful. regards BossShot Sign In·View Thread·PermaLink THE BUGG!!!!! SUPER_ZORRO 3:25 2 Dec '02   This bug is really exist. To test it -- open zip file, encrypt it, close HexEnc.exe, open it again, decrypt zip file, and try to extract! [Unexpected end of archive!] Also in Debug version you can see ASSERT MessageBox in CHexDoc::DeleteContents() then you open next file after encryption. UF!!!! But how to fix it fast? I dont want to use extra 16 Bytes of 'space'! Sign In·View Thread·PermaLink 2.00/5 HyperSnap? Joel Holdsworth 11:32 8 Jul '02   Just looking at your article, but I see that hypersnap has defaced your screenshot. I just thought I'd mention (in case you don't know) that if you press the print screen key a screen capture is sent to the clipboard, and if you press Alt + Print Screen you'll get a picture of the active window taken! You can then manipulate it or whatever... With time we live, with money we spend! Joel Holdsworth Sign In·View Thread·PermaLink

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