Merge pull request #1 from bricke/CFB-mode

CFB mode

Author: bricke

README.md

@@ -1,6 +1,6 @@
 # Qt-AES
 Small and portable AES encryption class for Qt.
-Supports all key sizes - 128/192/256 bits - ECB and CBC modes
+Supports all key sizes - 128/192/256 bits - ECB, CBC and CFB modes
 
 ## Usage
 

qaesencryption.cpp

@@ -273,14 +273,14 @@ void QAESEncryption::invShiftRows()
     it[11] = (quint8)temp;
 }
 
-QByteArray QAESEncryption::ivXor(const QByteArray in, const QByteArray iv)
+QByteArray QAESEncryption::byteXor(const QByteArray a, const QByteArray b)
 {
-  QByteArray::const_iterator it = in.begin();
-  QByteArray::const_iterator it_iv = iv.begin();
+  QByteArray::const_iterator it_a = a.begin();
+  QByteArray::const_iterator it_b = b.begin();
   QByteArray ret;
 
   for(int i = 0; i < m_blocklen; i++)
-      ret.insert(i,it[i] ^ it_iv[i]);
+      ret.insert(i,it_a[i] ^ it_b[i]);
 
   return ret;
 }
@@ -345,45 +345,78 @@ QByteArray QAESEncryption::invCipher(const QByteArray expKey, const QByteArray i
 
 QByteArray QAESEncryption::encode(const QByteArray rawText, const QByteArray key, const QByteArray iv)
 {
-    if (m_mode == CBC && (iv.isNull() || iv.size() != m_blocklen))
+    if (m_mode >= CBC && (iv.isNull() || iv.size() != m_blocklen))
        return QByteArray();
 
     QByteArray ret;
     QByteArray expandedKey = expandKey(key);
     QByteArray alignedText(rawText);
     QByteArray ivTemp(iv);
 
-
     alignedText.append(getPadding(rawText.size(), m_blocklen), 0); //filling the array with zeros
 
-    for(int i=0; i < alignedText.size(); i+= m_blocklen){
-        if (m_mode == CBC)
-            alignedText.replace(i, m_blocklen, ivXor(alignedText.mid(i, m_blocklen),ivTemp));
-
-        ret.append(cipher(expandedKey, alignedText.mid(i, m_blocklen)));
+    //Preparation for CFB
+    if (m_mode == CFB)
+        ret.append(byteXor(alignedText.mid(0, m_blocklen), cipher(expandedKey, iv)));
 
-        if (m_mode == CBC)
+    //Looping thru all blocks
+    for(int i=0; i < alignedText.size(); i+= m_blocklen){
+        switch(m_mode)
+        {
+        case ECB:
+            ret.append(cipher(expandedKey, alignedText.mid(i, m_blocklen)));
+            break;
+        case CBC:
+            alignedText.replace(i, m_blocklen, byteXor(alignedText.mid(i, m_blocklen),ivTemp));
+            ret.append(cipher(expandedKey, alignedText.mid(i, m_blocklen)));
             ivTemp = ret.mid(i, m_blocklen);
+            break;
+        case CFB:
+            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
+            break;
+        }
     }
     return ret;
 }
 
 QByteArray QAESEncryption::decode(const QByteArray rawText, const QByteArray key, const QByteArray iv)
 {
-    if (m_mode == CBC && (iv.isNull() || iv.size() != m_blocklen))
+    if (m_mode >= CBC && (iv.isNull() || iv.size() != m_blocklen))
        return QByteArray();
 
     QByteArray ret;
     QByteArray expandedKey = expandKey(key);
-    QByteArray alignedText(rawText);
     QByteArray ivTemp(iv);
 
-    for(int i=0; i < alignedText.size(); i+= m_blocklen){
-        ret.append(invCipher(expandedKey, alignedText.mid(i, m_blocklen)));
-
-        if (m_mode == CBC) {
-            ret.replace(i, m_blocklen, ivXor(ret.mid(i, m_blocklen),ivTemp));
-            ivTemp = alignedText.mid(i, m_blocklen);
+    //Preparation for CFB
+    if (m_mode == CFB)
+        ret.append(byteXor(rawText.mid(0, m_blocklen), cipher(expandedKey, iv)));
+
+    for(int i=0; i < rawText.size(); i+= m_blocklen){
+        switch(m_mode)
+        {
+        case ECB:
+            ret.append(invCipher(expandedKey, rawText.mid(i, m_blocklen)));
+            break;
+        case CBC:
+            ret.append(invCipher(expandedKey, rawText.mid(i, m_blocklen)));
+            ret.replace(i, m_blocklen, byteXor(ret.mid(i, m_blocklen),ivTemp));
+            ivTemp = rawText.mid(i, m_blocklen);
+            break;
+        case CFB:
+            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
+            break;
         }
     }
     return ret;

qaesencryption.h

@@ -16,7 +16,8 @@ class QAESEncryption : public QObject
 
     typedef enum {
         ECB,
-        CBC
+        CBC,
+        CFB
     } MODE;
 
     static QByteArray Crypt(QAESEncryption::AES level, QAESEncryption::MODE mode, const QByteArray rawText, const QByteArray key, const QByteArray iv = NULL);
@@ -77,7 +78,7 @@ public slots:
     void invShiftRows();
     QByteArray cipher(const QByteArray expKey, const QByteArray plainText);
     QByteArray invCipher(const QByteArray expKey, const QByteArray plainText);
-    QByteArray ivXor(const QByteArray in, const QByteArray iv);
+    QByteArray byteXor(const QByteArray in, const QByteArray iv);
 
     const quint8 sbox[256] =   {
       //0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F

unit_test/aestest.cpp

@@ -133,3 +133,21 @@ 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: