1 files changed, 65 insertions, 0 deletions

diff --git a/src/unstable/ciphermodeofb.h b/src/unstable/ciphermodeofb.h
new file mode 100644
index 0000000..19d0f83
--- /dev/null
+++ b/src/unstable/ciphermodeofb.h
@@ -0,0 +1,65 @@
+#ifndef BU_MODE_OFB_H
+#define BU_MODE_OFB_H
+
+#include "bu/filter.h"
+#include "bu/string.h"
+
+namespace Bu
+{
+    /**
+     * Output Feedback Mode.  This cipher mode is one of the most resiliant.
+     * Instead of encrypting your data directly it encrypts a "key stream" using
+     * the initialization vector, and then XORs those blocks with your stream
+     * blocks.  This means that an error in your stream will still produce an
+     * error in the output, but it will not propegate.  Also, with most
+     * encryption schemes error correction codes on the source data will still
+     * work on the encrypted data or decrypted output.
+     */
+    template<int iBlockSize, typename CipherType>
+    class CipherModeOfb : public CipherType
+    {
+    public:
+        CipherModeOfb(class Stream &rNext ) :
+            CipherType( rNext ),
+            bStart( true )
+        {
+            memset( aVector, 0, iBlockSize );
+        }
+
+        virtual ~CipherModeOfb()
+        {
+        }
+
+        void setIv( const Bu::String &sIv )
+        {
+            memcpy( aVector, sIv.getStr(), iBlockSize );
+        }
+
+    protected:
+        void decipher( void *pBuf )
+        {
+            CipherType::encipher( aVector );
+            uint8_t aTmp[iBlockSize];
+            memcpy( aTmp, aVector, iBlockSize );
+            for( int j = 0; j < iBlockSize; j++ )
+                ((uint8_t *)pBuf)[j] ^= aVector[j];
+            memcpy( aVector, aTmp, iBlockSize );
+        }
+
+        void encipher( void *pBuf )
+        {
+            CipherType::encipher( aVector );
+            uint8_t aTmp[iBlockSize];
+            memcpy( aTmp, aVector, iBlockSize );
+            for( int j = 0; j < iBlockSize; j++ )
+                ((uint8_t *)pBuf)[j] ^= aVector[j];
+            memcpy( aVector, aTmp, iBlockSize );
+        }
+
+    private:
+        bool bStart;
+        uint8_t aVector[iBlockSize];
+    };
+};
+
+#endif