adding CFB-mode

Author: Matteo Brichese

qaesencryption.cpp

@@ -356,10 +356,8 @@ QByteArray QAESEncryption::encode(const QByteArray rawText, const QByteArray key
     alignedText.append(getPadding(rawText.size(), m_blocklen), 0); //filling the array with zeros
 
     //Preparation for CFB
-    if (m_mode == CFB){
-        ivTemp = cipher(expandedKey, ivTemp);
-        ret.append(byteXor(alignedText.mid(0, m_blocklen), ivTemp));
-    }
+    if (m_mode == CFB)
+        ret.append(byteXor(alignedText.mid(0, m_blocklen), cipher(expandedKey, iv)));
 
     //Looping thru all blocks
     for(int i=0; i < alignedText.size(); i+= m_blocklen){
@@ -374,8 +372,9 @@ QByteArray QAESEncryption::encode(const QByteArray rawText, const QByteArray key
             ivTemp = ret.mid(i, m_blocklen);
             break;
         case CFB:
-            ivTemp = ret.mid(i, m_blocklen);
-            ret.append(byteXor(alignedText.mid(i, m_blocklen), cipher(expandedKey, ivTemp)));
+            if (i+m_blocklen < alignedText.size())
+                ret.append(byteXor(alignedText.mid(i+m_blocklen, m_blocklen),
+                                   cipher(expandedKey, ret.mid(i, m_blocklen))));
             break;
         default:
             //do nothing
@@ -392,29 +391,28 @@ QByteArray QAESEncryption::decode(const QByteArray rawText, const QByteArray key
 
     QByteArray ret;
     QByteArray expandedKey = expandKey(key);
-    QByteArray alignedText(rawText);
     QByteArray ivTemp(iv);
 
     //Preparation for CFB
-    if (m_mode == CFB){
-        ivTemp = cipher(expandedKey, ivTemp);
-        ret.append(byteXor(alignedText.mid(0, m_blocklen), ivTemp));
-    }
+    if (m_mode == CFB)
+        ret.append(byteXor(rawText.mid(0, m_blocklen), cipher(expandedKey, iv)));
 
-    for(int i=0; i < alignedText.size(); i+= m_blocklen){
+    for(int i=0; i < rawText.size(); i+= m_blocklen){
         switch(m_mode)
         {
         case ECB:
-            ret.append(invCipher(expandedKey, alignedText.mid(i, m_blocklen)));
+            ret.append(invCipher(expandedKey, rawText.mid(i, m_blocklen)));
             break;
         case CBC:
-            ret.append(invCipher(expandedKey, alignedText.mid(i, m_blocklen)));
+            ret.append(invCipher(expandedKey, rawText.mid(i, m_blocklen)));
             ret.replace(i, m_blocklen, byteXor(ret.mid(i, m_blocklen),ivTemp));
-            ivTemp = alignedText.mid(i, m_blocklen);
+            ivTemp = rawText.mid(i, m_blocklen);
             break;
         case CFB:
-            ivTemp = alignedText.mid(i, m_blocklen);
-            ret.append(byteXor(alignedText.mid(i, m_blocklen), cipher(expandedKey, ivTemp)));
+            if (i+m_blocklen < rawText.size()){
+                ret.append(byteXor(rawText.mid(i+m_blocklen, m_blocklen),
+                                   cipher(expandedKey, rawText.mid(i, m_blocklen))));
+            }
             break;
         default:
             //do nothing

unit_test/aestest.cpp

@@ -4,6 +4,8 @@
 #include <QCryptographicHash>
 #include "qaesencryption.h"
 
+#include <QDebug>
+
 void AesTest::initTestCase()
 {
     quint8 key_16[16] =  {0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c};
@@ -133,3 +135,21 @@ void AesTest::CBC128Decrypt()
 
     QCOMPARE(encryption.decode(outCBC128, key16, iv), inCBC128);
 }
+
+//=================== CFB TESTING ============================
+
+void AesTest::CFB256String()
+{
+    QAESEncryption encryption(QAESEncryption::AES_256, QAESEncryption::CFB);
+
+    QString inputStr("The Advanced Encryption Standard (AES), also known by its original name Rijndael "
+                        "is a specification for the encryption of electronic data established by the U.S. "
+                        "National Institute of Standards and Technology (NIST) in 2001");
+    QString key("123456789123");
+
+    QByteArray hashKey = QCryptographicHash::hash(key.toLocal8Bit(), QCryptographicHash::Sha256);
+
+    QByteArray encodeText = encryption.encode(inputStr.toLocal8Bit(), hashKey, iv);
+
+    QCOMPARE(QString(encryption.decode(encodeText, hashKey, iv)), inputStr);
+}

unit_test/aestest.h

@@ -25,6 +25,8 @@ private slots:
     void CBC128Crypt();
     void CBC128Decrypt();
 
+    void CFB256String();
+
     void cleanupTestCase(){}
 
 private: