fam

aesFINISHED/decryptAESCBC.py

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+import sys
+import os
+import getpass
+import itertools
+from Crypto.Cipher import AES
+from Crypto.Hash import MD5, SHA256
+
+
+# generates key based on password
+def generatekey(pw):
+    password = pw   # getpass.getpass('Password for decryption: ')
+    #print(password)
+    h = MD5.new()
+    h.update(password.encode())
+    #h.update(password)
+    return h.digest()
+
+def generatePass():
+    temp = []
+    alpha = ["a", "z", "e", "r", "t", "y", "u", "i", "o", "p"]
+    for i in itertools.product(alpha, repeat=6):
+        temp.append(generatekey("".join(i)))
+    return temp
+
+# calculates and return hash for message
+def calculatehash(message):
+    h = SHA256.new()
+    h.update(message)
+    # use hexdigest to prevent problems with control characters
+    # e.g. \r in charcter 5, appends 4, then overwrites beginning of message with rest of digest
+    return h.hexdigest()
+
+
+# check integrity and return cleartext or error message
+def checkintegrity(decryptedcontent):
+    return calculatehash(decryptedcontent[0:-64]).encode() == decryptedcontent[-64:]
+
+
+# encrypts content in AES CBC mode
+def decrypt_AES_CBC(inputfilename, encryptedContent):
+    # create encrypted filename, keep extension
+    outputfilename = inputfilename[0:inputfilename.find('.', len(inputfilename) - 5)] \
+                     + '_decrypted' + inputfilename[inputfilename.find('.'):len(inputfilename)]
+
+    i = 0
+    keys = generatePass()
+    print(len(keys))
+    for key in keys:
+        decipher = AES.new(key, AES.MODE_CBC)
+        decryptedcontent = decipher.decrypt(encryptedContent)
+        ivlength = 16
+        # remove iv and padding
+        decryptedcontent = decryptedcontent[ivlength:-decryptedcontent[-1]]
+        # check Integrity and retain cleartext
+        if checkintegrity(decryptedcontent):
+            cleartext = decryptedcontent[0:-64]
+            outputfile = open(outputfilename, 'wb')
+            outputfile.write(cleartext)
+            outputfile.close
+            outputfilename = outputfilename+"EXTRA"
+        else:
+            cleartext = 'Integrity check error'.encode()
+            print("error:{}".format(i))
+            i = i+1
+    print("done?")
+
+    return
+
+#
+#
+#    key = generatekey()
+#    decipher = AES.new(key, AES.MODE_CBC)
+#    decryptedcontent = decipher.decrypt(encryptedContent)
+#
+#    ivlength = 16
+#    # remove iv and padding
+#    decryptedcontent = decryptedcontent[ivlength:-decryptedcontent[-1]]
+#
+#    # check Integrity and retain cleartext
+#    if checkintegrity(decryptedcontent):
+#        cleartext = decryptedcontent[0:-64]
+#    else:
+#        cleartext = 'Integrity check error'.encode()
+#
+#    # useful only for decrypted text files
+#    # print(cleartext)
+#
+#    # write to file
+#    outputfile = open(outputfilename, 'wb')
+#    outputfile.write(cleartext)
+#    outputfile.close()
+
+
+for i in sys.argv[1:]:
+
+    inputfilename = i
+
+    print('decrypting ' + inputfilename)
+
+    try:
+        inputfile = open(inputfilename, 'rb')
+    except IOError:
+        print("File " + inputfilename + " not found, working directory: " + os.getcwd())
+        continue
+    else:
+        # if file opened, read content into variable
+        content = inputfile.read()
+        inputfile.close()
+
+    # apply symmetric encryption
+    decrypt_AES_CBC(inputfilename, content)
+    # encrypt_AES_ECB(inputfilename,content)