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Forum Update on Monday, May 27th 2025

Decrypt AES with OpenSSL & Qt 5.5.1 Win32 VS2013

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opensslqt 5.5.1windowsvs 2013decrypt
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  • hskoglundH Offline
    hskoglundH Offline
    hskoglund
    wrote on last edited by
    #2

    Hi, don't know about the OpenSSL block lengths problem, but the reason you're crashing I think is because you're allocating memory badly, for example
    unsigned char *plaintext = (unsigned char*) ""; is almost always guaranteed to crash.
    Why not skip the QStrings, do something simpler like this:

    ...
    unsigned char cypher[] = "PpUr+LMHvaKmf0q6J7Oyzo4jbFO5kfWyXl0d8nD3hyM=";
    unsigned char pw_md5[] = "098f6bcd4621d373cade4e832627b4f6";
    unsigned char iv16[] = "d8e8fca2dc0f896fd7cb4cb0031ba249";
    
    ERR_load_crypto_strings();
    OpenSSL_add_all_algorithms();
    OPENSSL_config(NULL);
    
    unsigned char *ciphertext = cypher;
    int ciphertext_len = sizeof(cypher) - 1;
    unsigned char *key = pw_md5;
    unsigned char *iv = iv16;
    unsigned char plaintext[1024];
    ...
    

    Now the app shouldn't crash, so you can try debugging the OpenSSL decrypting stuff...

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    1
    • Q Offline
      Q Offline
      qDebug
      wrote on last edited by
      #3

      Thanks to you, no more crashing. :D

      Tank you!

      Still getting wrong last black error. But at least i can try to fix that somehow. I was guessing some Qt users may use Openssl and got experience using it with Qt.

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      0
      • SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #4

        Hi,

        Depending on your needs the QCA module might be something to look into.

        Interested in AI ? www.idiap.ch
        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

        Q 1 Reply Last reply
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        • SGaistS SGaist

          Hi,

          Depending on your needs the QCA module might be something to look into.

          Q Offline
          Q Offline
          qDebug
          wrote on last edited by qDebug
          #5

          @SGaist Thanks, but it is no option for me. Did load qca-2.1.0 and also did try to compile it on Windows VS2013 and cmake. No chance i will get this running without a step my step tutorial for Win. I did try to compile it on Ubuntu, no problem, works instantly, Windows, nah. I will look into this module again if i ever reach a level called ultra skilled hacker.

          Also tryed Crypto++ and was able to get some code running, but the sample codes do not work for me and the docs are not really helpful.

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          • SGaistS Offline
            SGaistS Offline
            SGaist
            Lifetime Qt Champion
            wrote on last edited by SGaist
            #6

            To avoid the need to level-up that high: open the QCA project in Qt Creator and build it with the Kit you are using for your project, then install it and you should be done. IIRC, you can even choose the install target from the list in the Project panel.

            Interested in AI ? www.idiap.ch
            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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            • Q Offline
              Q Offline
              qDebug
              wrote on last edited by
              #7

              Thank you!

              But no luck, it won't compile. 5 errors.

              C2061: syntax error : identifier 'QIODevice'
              C2065: 'QIODevice' : undeclared identifier
              C2065: 'file' : undeclared identifier
              C2448: 'QCA::Hash::update' : function-style initializer appears to be a function definition
              C2061: syntax error : identifier 'QIODevice'
              
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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #8

                Where did you get QCA from ?

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                Q 1 Reply Last reply
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                • SGaistS SGaist

                  Where did you get QCA from ?

                  Q Offline
                  Q Offline
                  qDebug
                  wrote on last edited by qDebug
                  #9

                  @SGaist Thank you for asking. I got it from http://delta.affinix.com/qca/ (qca-2.1.0.tar.gz).

                  Edit: Did find a newer version @ https://www.freshports.org/devel/qca-qt5/ (qca-2.1.1.tar.xz) and i was able to compile it. At least the debug files did compile. But the big problem is

                  if(!QCA::isSupported("aes128"))
                  {
                       qDebug() << "No AES 128 supported ...";
                  }
                  if(!QCA::isSupported("aes128-cbc"))
                  {
                       qDebug() << "No AES 128  CBC supported ...";
                  }
                  if(!QCA::isSupported("aes128-cbc-pkcs7"))
                  {
                       qDebug() << "No AES 128 CBS pkcs7 supported ...";
                  }
                  

                  According to the docs http://delta.affinix.com/docs/qca/ my version does not support AES CBC at all so it is worthless to me atm. Did i something wrong here?

                  win32: LIBS += -L$$PWD/qca/lib/ -lqca-qt5d
                  INCLUDEPATH += $$PWD/qca/include
                  DEPENDPATH += $$PWD/qca/include
                  

                  and

                  #include <QtCrypto/QtCrypto>
                  

                  Thanks!

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                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #10

                    CBS ? Don't you mean CBC ? If CBC, then yes it does, just take a look at QCA's code.

                    Before calling these function did you initialize QCA ?

                    Also, do you have OpenSSL in your PATH environment variable when running the application ?

                    Interested in AI ? www.idiap.ch
                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                    • Q Offline
                      Q Offline
                      qDebug
                      wrote on last edited by qDebug
                      #11

                      Yes, CBC, sorry.

                      I did put a QCA::Initializer init; after ui->setupUi(this); And yes, Openssl is in my paths env (C:\OpenSSL-Win32\bin), i can call openssl.exe from command line.

                      cmake tells me:

                      qca-botan off
                      qca-cyrus-sasl off
                      qca-gcrypt off
                      qca-gnupg on
                      qca-logger on
                      qca-nss off
                      qca-ossl on
                      qca-pkcs11 off
                      qca-softstore on
                      

                      Do you know if i need one or more plugins to use AES 128 CBC?

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                      • Q Offline
                        Q Offline
                        qDebug
                        wrote on last edited by
                        #12

                        I've mastered the installation now. After building it with Qt Creator i went to the build directory and executed a nmake install. After editing the include paths i also had to add CONFIG += crypto in my pro file. So far no more AES128 CBC not supported errors. But still no luck in decrypting my string.

                        QString ciphertext = "PpUr+LMHvaKmf0q6J7Oyzo4jbFO5kfWyXl0d8nD3hyM=";
                        QString key1 = "098f6bcd4621d373cade4e832627b4f6";
                        QString iv1 = "507055722b4c4d4876614b6d66307136";
                        
                        QByteArray key;
                        key = key1.toLatin1();
                        
                        QByteArray iv;
                        iv = iv1.toLatin1();
                        
                        QCA::SecureArray arg = ciphertext.toLatin1();
                        QCA::Cipher cipher(QString("aes128"),QCA::Cipher::CBC, QCA::Cipher::NoPadding, QCA::Decode, key, iv);
                        
                        QCA::SecureArray plainText = cipher.update(arg);
                        if(!cipher.ok())
                        {
                        	qDebug() << "update fail";
                        }
                        plainText = cipher.final();
                        if(!cipher.ok())
                        {
                        	qDebug() << "final fail";
                        }
                        
                        qDebug() << "plainText.data(): " << plainText.data();
                        

                        The decrypted text should be Dr. Test and password is test. The iv are the fist 16 bytes from the ciphertext and the password is a md5 hash from test. Works in openssl command line. I get a qDebug final fail result.

                        Any ideas about that?

                        Thanks!

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                        0
                        • Q Offline
                          Q Offline
                          qDebug
                          wrote on last edited by
                          #13

                          I'm doing something wrong and i can't figure out what. Changed to utf8, plain key and iv, vise versa, but somehow i won't get this example decrypted. It does work this way in the openssl command line tool.

                          So far i did not find any example code that used a custom key and iv, only random generated ones. Also gave QCA::SymmetricKey::SymmetricKey(key) and QCA::InitializationVector::InitializationVector(iv) a chance, did not really help.

                          Any ideas?

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                          • SGaistS Offline
                            SGaistS Offline
                            SGaist
                            Lifetime Qt Champion
                            wrote on last edited by
                            #14

                            Your code doesn't match all the openssl line options. -a -A means that you must first decode your Base64 encoded string.

                            Interested in AI ? www.idiap.ch
                            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                            Q 1 Reply Last reply
                            1
                            • SGaistS SGaist

                              Your code doesn't match all the openssl line options. -a -A means that you must first decode your Base64 encoded string.

                              Q Offline
                              Q Offline
                              qDebug
                              wrote on last edited by qDebug
                              #15

                              @SGaist Thanks! I don't know why but i did forget about the base64 decode. After changing from toLatin1 to toUtf8 and decode the base64 string i don't get the final error anymore. But i won't get the expected plain text only

                              o????:??????a?s?]??Iy?[W6???l??(f?$?I{??^ ????Cï5?
                              

                              same result if i use

                              qDebug() << "process: " << QCA::SecureArray(cipher.process(decodedBase64.toUtf8())).data();
                              

                              Maybe the utf8 conversion is the problem but it won't take a QString. I get the same result if i append the string to a QByteArray. Btw. noting changes if i use QByteArray to decode base64 or QCA::Base64 decoder(QCA::Decode);

                              At least the final error is gone, that's some progress! ;)

                              Edit: And i added "md5" as crypto service provider because it was encoded this way. md5 is in the list of providers, so i hope i implemented this correctly.

                              QCA::Cipher cipher(QString("aes128"), QCA::Cipher::CBC, QCA::Cipher::NoPadding, QCA::Decode, key, iv, "md5");
                              

                              But cipher.provider()->name(); returns "qca-ossl".

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                              • SGaistS Offline
                                SGaistS Offline
                                SGaist
                                Lifetime Qt Champion
                                wrote on last edited by
                                #16

                                Do you mean that you passed your original string through md5 before encrypting it ?

                                Interested in AI ? www.idiap.ch
                                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                • Q Offline
                                  Q Offline
                                  qDebug
                                  wrote on last edited by qDebug
                                  #17

                                  The password / key was md5 hashed.

                                  key = md5(utf8(password));
                                  

                                  and the iv are the first 16 bytes from the base64 string.

                                  Edit: Not the key of course, the iv are the first 16 bytes from the base64 string.

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                                  • SGaistS Offline
                                    SGaistS Offline
                                    SGaist
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #18

                                    Can you show the complete procedure ?

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                                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                    • Q Offline
                                      Q Offline
                                      qDebug
                                      wrote on last edited by
                                      #19

                                      Thanks for asking. This is the VB code to encrypt the string:

                                      Dim AES As New RijndaelManaged
                                      
                                      Dim md5 As New MD5CryptoServiceProvider
                                      Dim key() As Byte = md5.ComputeHash(Encoding.UTF8.GetBytes(password))
                                      
                                      md5.Clear()
                                      AES.Key = key
                                      AES.GenerateIV()
                                      Dim iv() As Byte = AES.IV
                                      Dim ms As New MemoryStream
                                      
                                      ms.Write(iv, 0, iv.Length)
                                      
                                      Dim cs As New CryptoStream(ms, AES.CreateEncryptor, CryptoStreamMode.Write)
                                      Dim data() As Byte = System.Text.Encoding.UTF8.GetBytes(string)
                                      
                                      cs.Write(data, 0, data.Length)
                                      cs.FlushFinalBlock()
                                      
                                      Dim encoded() As Byte = ms.ToArray()
                                      Return (Convert.ToBase64String(encoded))
                                      cs.Close()
                                      AES.Clear()
                                      

                                      As far as i can tell is the password and the string are utf8 bytes and the password is the md5 hash of it. I did try to pass it through

                                      QCA::SecureArray key = QCA::SecureArray::SecureArray(password);
                                      

                                      before and after utf8 and md5. So far no luck.

                                      Thank you!

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                                      • Q Offline
                                        Q Offline
                                        qDebug
                                        wrote on last edited by
                                        #20

                                        And this is my attempt:

                                        QString MainWindow::decryptString(QString password, QString encodedString)
                                        {
                                            // final decodec string
                                            QString decodedString;
                                        
                                            // get the iv
                                            QByteArray array(encodedString.left(16).toStdString().c_str(), encodedString.left(16).size());
                                            QCA::SecureArray iv = array.toHex();
                                        
                                            // decode base64
                                            QCA::Base64 decoder(QCA::Decode);
                                            const char* decoded = decoder.decodeString(encodedString).toStdString().c_str();
                                        
                                            QCA::SecureArray key = QByteArray(QCryptographicHash::hash(password.toUtf8(), QCryptographicHash::Md5).toHex());
                                            QCA::SecureArray arg = decoded;
                                        
                                            QCA::Cipher cipher(QString("aes128"), QCA::Cipher::CBC, QCA::Cipher::NoPadding, QCA::Decode, key, iv);
                                            QCA::SecureArray plainText = cipher.update(arg);
                                        
                                            if(!cipher.ok())
                                            {
                                                qDebug() << "update Fail";
                                            }
                                        
                                            cipher.final();
                                            if(!cipher.ok())
                                            {
                                                qDebug() << "final fail";
                                            }
                                        
                                            qDebug() << "process: " << QCA::SecureArray(cipher.process(decoded)).data();
                                        
                                            decodedString = plainText.data();
                                            qDebug() << "Decoded: " << decodedString;
                                        
                                            return decodedString;
                                        }
                                        

                                        I call it like:

                                        qDebug() << "decoded: " << decryptString("test", "PpUr+LMHvaKmf0q6J7Oyzo4jbFO5kfWyXl0d8nD3hyM=");
                                        

                                        The only step i masted was getting rid of the final fail, but i don't know if that was really the case. Not sure how, i changed this so often, i don't even know how much time i spend on this. I didn't think it can be that difficult to use it.

                                        So far i still did not fine one single example code using qca with aes128cbc and custom iv and key. Very, very strange.

                                        Any ideas?

                                        Thanks!

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                                        • SGaistS Offline
                                          SGaistS Offline
                                          SGaist
                                          Lifetime Qt Champion
                                          wrote on last edited by
                                          #21

                                          Do you mean this example ?

                                          Interested in AI ? www.idiap.ch
                                          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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