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New SimpleCrypt page

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  • A Offline
    A Offline
    andre
    wrote on last edited by
    #15

    I have added a "separate page":http://developer.qt.nokia.com/wiki/SimpleCrypt_algorithm_details that details the algorithm and the layout of the cypher text. Of course, I also added a link from the main page.

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    • P Offline
      P Offline
      paucoma
      wrote on last edited by
      #16

      Hi Andre,
      First: Thanks for sharing the code.

      Second: You've got some typos in the Example usage code.

      • Name of the Class: SimpleCypt --> SimpleCrypt
      • crypto.setCompression(SimpleCrypto::CompressionAlways)
        ** crypto.setCompressionMode(SimpleCrypt::CompressionAlways);
      • crypto.setIntegrityProtection(SimpleCrypto::ProtectHash);
        ** crypto.setIntegrityProtectionMode(SimpleCrypt::ProtectionHash);
      • SimpleCrypt.ErrorNoError --> SimpleCrypt::ErrorNoError

      Third:
      The String Encryption and Decryption works fine, but for the binary version I seem to be having some difficulties.

      my main.cpp
      @
      #include "simplecrypt.h"

      #include <QString>
      #include <QDebug>
      #include <QBuffer>
      #include <QDataStream>

      int main(){
      QString txStr = "Hello world!";

      SimpleCrypt crypto(Q_UINT64_C(0x7F29B208)); //some random number
      // crypto.setCompressionMode(SimpleCrypt::CompressionAlways);
      // crypto.setIntegrityProtectionMode(SimpleCrypt::ProtectionHash);
      QBuffer txB;
      QDataStream s(&txB);
      s << txStr;

      QByteArray cypherBytes = crypto.encryptToByteArray(txB.data());
      if (crypto.lastError() == SimpleCrypt::ErrorNoError) {
      qDebug() << cypherBytes;
      }

      SimpleCrypt cryptu(Q_UINT64_C(0x7F29B208)); //some random number
      QByteArray plainBytes = cryptu.decryptToByteArray(cypherBytes);
      if (!cryptu.lastError() == SimpleCrypt::ErrorNoError) {
      qDebug() << "decrypt error";
      return 0;
      }
      qDebug() << plainBytes;

      QString rxStr;
      QBuffer rxB(&plainBytes);
      QDataStream rs(&rxB);
      rs >> rxStr;
      qDebug() << rxStr;
      return 0;
      }
      @

      My Output (console):

      "??Sß+"
      ""
      ""

      What have I missed or using incorrectly?

      Thanks again for the contribution.

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      • P Offline
        P Offline
        paucoma
        wrote on last edited by
        #17

        So I've played a bit around I've come to the conclusion that I'm using QDataStream incorrectly.

        My Test Code: main.cpp
        @
        #include <QString>
        #include <QDebug>
        #include <QBuffer>
        #include <QDataStream>
        int main(){
        QString txStr = "Hello world!";
        QString rxStr;

        QBuffer txB;
        txB.open(QIODevice::ReadWrite);
        QDataStream s(&txB);
        qDebug() << txB.size();
        s << txStr;
        qDebug() << txB.size();
        s >> rxStr;
        qDebug() << rxStr;
        return 0;
        }
        @

        My Output:
        0
        28
        ""

        So the buffer is being filled but not correctly being read out.. why not?

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        • G Offline
          G Offline
          giesbert
          wrote on last edited by
          #18

          That's an easy question. Your problem is the stream position:

          you write to the stream, then start reading after the written bytes :-)

          try out the following:

          @
          #include <QString>
          #include <QDebug>
          #include <QBuffer>
          #include <QDataStream>
          int main()
          {
          QString txStr = "Hello world!";
          QString rxStr;

          QBuffer txB;
          txB.open(QIODevice::WriteOnly);
          QDataStream s(&txB);
          qDebug() << txB.size();
          s << txStr;
          qDebug() << txB.size();
          txB.close(); // sets stream position to 0 !!!
          
          txB.open(QIODevice::ReadOnly);
          QDataStream s2(&txB);
          s2 >> rxStr;
          qDebug() << rxStr;
          return 0;
          

          }
          @

          or use a seek in between

          @
          #include <QString>
          #include <QDebug>
          #include <QBuffer>
          #include <QDataStream>
          int main()
          {
          QString txStr = "Hello world!";
          QString rxStr;

          QBuffer txB;
          txB.open(QIODevice::WriteOnly);
          QDataStream s(&txB);
          qDebug() << txB.size();
          s << txStr;
          qDebug() << txB.size();
          txB.seek(0); // sets stream position to 0 !!!
          s >> rxStr;
          qDebug() << rxStr;
          return 0;
          

          }
          @

          I did not compile the code, so it might contain typos

          Nokia Certified Qt Specialist.
          Programming Is Like Sex: One mistake and you have to support it for the rest of your life. (Michael Sinz)

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          • P Offline
            P Offline
            paucoma
            wrote on last edited by
            #19

            Aha, got it all sorted out, thanks

            I had my suspicions on that, but thought that the "<<" and ">>" operators may use seperate index variables.

            Andre: it would be great if you could incorporate in the Example usage code the following so it works out of the box.

            @
            buffer.open(QIODevice::WriteOnly);
            buffer.close();
            buffer.open(QIODevice::ReadOnly);
            @

            Because newbies like myself:

            • copy + paste + compile
              ** if it works -> adapt to needs
              ** if it doesn't -> get lost in the simplest things

            Although I must admit that I am learning loads of things through all these problems I get myself into.

            Gerolf: Once again thanks for your quick and effective response.

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            • A Offline
              A Offline
              andre
              wrote on last edited by
              #20

              paucoma, thank you for your comments and suggestions. I have changed the wiki page accordingly. I am glad you solved the problem, and that it turned out the class itself was not at fault ;-)

              I must admit that I wrote the examples directly in the wiki page, and thats when errors like these happen. Sorry about that! I hope the current version is more managable? Note that I was talking about "at the other end", implying that the decryption code was not meant to be used in the same function (and thus, implicitly, with the same buffer).

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              • P Offline
                P Offline
                paucoma
                wrote on last edited by
                #21

                Thanks Andre for making the modifications.

                I have corrected myself a few other details I found.

                P.S. I didn't know that I had such a priviledge.

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                • A Offline
                  A Offline
                  andre
                  wrote on last edited by
                  #22

                  Thanks for your effort, I really appreciate it. If you want, you're welcome to update it yourself in the wiki article :-)

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                  • G Offline
                    G Offline
                    giesbert
                    wrote on last edited by
                    #23

                    Hi Andre,

                    one suggestion to the wiki page:
                    In the section SimpleCrypt in use it would be nice to have a list of the encryp/decrypt functions. You state thete are two times 4, but not the names :-)
                    this means searching inside the code :-)

                    The rest sound really god. Thanks for the article.

                    Nokia Certified Qt Specialist.
                    Programming Is Like Sex: One mistake and you have to support it for the rest of your life. (Michael Sinz)

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                    • A Offline
                      A Offline
                      andre
                      wrote on last edited by
                      #24

                      [quote author="Gerolf" date="1300958192"]Hi Andre,

                      one suggestion to the wiki page:
                      In the section SimpleCrypt in use it would be nice to have a list of the encryp/decrypt functions. You state thete are two times 4, but not the names :-)
                      this means searching inside the code :-)

                      The rest sound really god. Thanks for the article.[/quote]

                      Fair enough, done. :-)

                      Thanks for the praise.

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                      • G Offline
                        G Offline
                        giesbert
                        wrote on last edited by
                        #25

                        Hi Andre,

                        I'm currently reading your second article, and found the following "here":http://developer.qt.nokia.com/wiki/SimpleCrypt_algorithm_details#00f4e5788aab6d3546bb433842dbbefc :

                        bq. The payload data block’s contents are encrypted with a four byte (quint64) key.

                        quint64 is a 64 bit integer, which means 8 byte.

                        so also in the snipet page, you say:

                        @
                        SimpleCrypt crypto(Q_UINT64_C(0x7F29B208)); //some random number
                        @

                        this is just a 32 bit number, not 64 bit.

                        @
                        void SimpleCrypt::splitKey()
                        {
                        m_keyParts.clear();
                        m_keyParts.resize(4);
                        for (int i=0;i<4;i++) {
                        quint64 part = m_key;
                        for (int j=i; j>0; j--)
                        part = part >> 8;
                        part = part & 0xff;
                        m_keyParts[i] = static_cast<char>(part);
                        }
                        }
                        @

                        this also only uses 4 bytes, not 8.

                        Nokia Certified Qt Specialist.
                        Programming Is Like Sex: One mistake and you have to support it for the rest of your life. (Michael Sinz)

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                        • G Offline
                          G Offline
                          giesbert
                          wrote on last edited by
                          #26

                          some additional topics:

                          in "Decrypted payload":http://developer.qt.nokia.com/wiki/SimpleCrypt_algorithm_details#2d478ba9ee3cf03e338b506b1a0292dc

                          SH1 and CRC have the same description:

                          bq. In case the Protection Checksum flag has been set, the layout of the decrypted payload looks like this:

                          I think this is just a copy paste error.

                          As I'm through now, no more things :-)
                          Very good article, interesting to read. Thanks.

                          Nokia Certified Qt Specialist.
                          Programming Is Like Sex: One mistake and you have to support it for the rest of your life. (Michael Sinz)

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                          • A Offline
                            A Offline
                            andre
                            wrote on last edited by
                            #27

                            Thank you very much for this catch, Gerolf! You are absolutely right, and this is a big mistake in the algorithm as well. I will take care of fixing this ASAP.

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                            • A Offline
                              A Offline
                              andre
                              wrote on last edited by
                              #28

                              OK, fixed on both pages. Very embarrassing, I must say. :(

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                              • G Offline
                                G Offline
                                giesbert
                                wrote on last edited by
                                #29

                                Now it looks good, thanks :-)

                                Nokia Certified Qt Specialist.
                                Programming Is Like Sex: One mistake and you have to support it for the rest of your life. (Michael Sinz)

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                                • L Offline
                                  L Offline
                                  luca
                                  wrote on last edited by
                                  #30

                                  I tried today SimpleCrypt class and it was very useful.

                                  Thanks!

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                                  • A Offline
                                    A Offline
                                    andre
                                    wrote on last edited by
                                    #31

                                    Glad you like it!

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                                    • C Offline
                                      C Offline
                                      cincirin
                                      wrote on last edited by
                                      #32

                                      Hi Andre.
                                      First of all, thanks for sharing your code. :-)

                                      I was playing with this algorithm, but I noticed a strange situation: sometimes these work well, sometimes not.

                                      This is the string which I have tested :
                                      10197016915918185882701231384169178913312058269-10750535699546572956586080750006397
                                      The key is: 13775729

                                      I tested both with string and binary data (there are several integer values).

                                      So if I encrypt this string, and then decrypt it, sometimes original string is equal with decrypted string, sometimes differ.

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                                      • A Offline
                                        A Offline
                                        andre
                                        wrote on last edited by
                                        #33

                                        You'll have to provide a small testprogram that shows the problem, otherwise I can not help you debug the issue.

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                                        • C Offline
                                          C Offline
                                          cincirin
                                          wrote on last edited by
                                          #34

                                          A small test is something like :

                                          @
                                          QString cryptSerialNumber;

                                          void testCrypt()
                                          {
                                          SimpleCrypt processSimpleCrypt(13775729);
                                          QString uniqueString("10197016915918185882701231384169178913312058269-10750535699546572956586080750006397");
                                          cryptSerialNumber = processSimpleCrypt.encryptToString(uniqueString);
                                          }

                                          void testDecrypt()
                                          {
                                          SimpleCrypt processSimpleCrypt(13775729);
                                          QString uniqueString = processSimpleCrypt.decryptToString(cryptSerialNumber);
                                          }
                                          @

                                          Sometimes decrypted "uniqueString" is the same as the original, but sometimes is :
                                          1019701691591818588270123138416917891691033658269-10750535699546572956586080750006397, almost the same with original, but not the same :-)

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