first release. readme will follow up

utility_aes.py

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+import hashlib,os
+from utility import read_in_chunks
+
+try:
+    pycrypto = True
+    from Crypto.Cipher import AES
+    from Crypto import Random
+    print("Using PyCrypto for AES enc/dec")
+except ImportError:
+    pycrypto = False
+    import pyaes
+    print("Using Pyaes for AES enc/dec")
+
+
+
+class AESCipherFile:
+    def __init__( self ,f,d, size_limit_reading_os, key ):
+        h = hashlib.sha256()
+        h.update(key.encode("utf_8"))
+        self.key = h.digest()
+        self.f = f
+        self.d = d
+        self.size_limit_reading_os = size_limit_reading_os
+
+    def pad(self,b):
+        b = bytearray(b)
+        fill = 16 - len(b) % 16
+        for i in range(fill):
+            b.append(fill)
+        return bytes(b)
+
+    def unpad(self,b) :
+        return b[:-b[len(b)-1]]
+
+
+    def encrypt( self ):
+        if pycrypto:
+            iv = Random.new().read( 16 )
+            aes_encrypt_state = AES.new( self.key, AES.MODE_CBC, iv )
+        else:
+            iv = os.urandom(16)
+            aes_encrypt_state = pyaes.AESModeOfOperationCBC(self.key, iv = iv)
+        #check if the file is a multiple of 16 bytes for padding
+        self.f.seek(0,2)
+        if self.f.tell() % 16 == 0:
+            self.d.write(bytes(b"1"))
+        else:
+            self.d.write(bytes(b"0"))
+        self.f.seek(0,0)
+        #end check
+        self.d.write(iv)
+        hash = hashlib.md5()
+        for piece in read_in_chunks(self.f,self.size_limit_reading_os):
+            hash.update(piece)
+            if len(piece) % 16 > 0 :
+                piece = self.pad(piece)
+            steps = int(len(piece) / 16)
+            for i in range(steps):
+                self.d.write(aes_encrypt_state.encrypt( piece[16 * i : 16 * (i + 1)] ))
+        return hash.hexdigest()
+
+    def decrypt( self ):
+        perfect = False
+        perfectbyte = self.f.read(1)
+        if perfectbyte == bytes(b"1"):
+            perfect = True
+        if pycrypto:
+            aes_decrypt_state = AES.new( self.key, AES.MODE_CBC, self.f.read(16) )
+        else:
+            aes_decrypt_state = pyaes.AESModeOfOperationCBC(self.key, self.f.read(16))
+        last_16_bytes_in_piece = None
+        for piece in read_in_chunks(self.f,self.size_limit_reading_os):
+            if last_16_bytes_in_piece != None:
+               self.d.write(aes_decrypt_state.decrypt(last_16_bytes_in_piece))
+            steps = int(len(piece) / 16)
+            if steps > 1 :
+                for i in range(steps - 1):
+                    self.d.write(aes_decrypt_state.decrypt( piece[16 * i : 16 * (i + 1)] ))
+                i = i + 1
+            else:
+                i = 0
+            last_16_bytes_in_piece = aes_decrypt_state.decrypt( piece[16 * i : 16 * (i + 1)] )
+        if last_16_bytes_in_piece != None:
+            if perfect:
+                self.d.write(last_16_bytes_in_piece)
+            else:
+                self.d.write(self.unpad(last_16_bytes_in_piece))
+
+
+
+''' usage
+with open("c:\\test\\file", 'rb') as f:
+    with open("c:\\test\\file_enc", 'wb') as d:
+        aes = AESCipherFile(f,d,134217728,"chiave")
+        aes.encrypt()
+with open("c:\\test\\file_enc", 'rb') as f:
+    with open("c:\\test\\file", 'wb') as d:
+        aes = AESCipherFile(f,d,134217728,"chiave")
+        aes.decrypt()
+'''
+
+