Index: pyAES.txt
===================================================================
--- pyAES.txt	(revision 15)
+++ pyAES.txt	(working copy)
@@ -1,6 +1,7 @@
 #!/usr/bin/python2.5
 import sys, hashlib, string, getpass
 from copy import copy
+from random import randint
 
 # The actual Rijndael specification includes variable block size, but
 # AES uses a fixed block size of 16 bytes (128 bits)
@@ -332,7 +333,9 @@
     block = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] # plaintext
     ciphertext = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] # ciphertext
     # Initialization Vector
-    IV = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
+    IV = []
+    for i in range(16):
+        IV.append(randint(0, 255))
 
     # convert password to AES 256-bit key
     aesKey = passwordToKey(password)
@@ -359,6 +362,18 @@
             print "pyAES: unable to open output file -", filename
             sys.exit()
 
+    # write IV to outfile
+    for byte in IV:
+        outfile.write(chr(byte))
+
+    # get the file size (bytes) 
+    # if the file size is a multiple of the block size, we'll need 
+    # to add a block of padding at the end of the message
+    fp.seek(0,2)
+    filesize = fp.tell()
+    # put the file pointer back at the beginning of the file
+    fp.seek(0)
+
     # begin reading in blocks of input to encrypt
     firstRound = True
     block = getBlock(fp)
@@ -378,6 +393,10 @@
 
         # grab next block from input file
         block = getBlock(fp)
+    # if the message ends on a block boundary, we need to add an
+    # extra block of padding
+    if filesize % 16 == 0:
+        outfile.write(16*chr(16))
     # close file pointers
     fp.close()
     outfile.close()
@@ -387,8 +406,6 @@
 def decrypt(myInput, password, outputfile=None):
     block = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] # ciphertext
     plaintext = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] # plaintext container
-    # Initialization Vector
-    IV = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
 
     # convert password to AES 256-bit key
     aesKey = passwordToKey(password)
@@ -400,13 +417,6 @@
         print "pyAES: unable to open input file -", myInput
         sys.exit()
 
-    # get the file size (bytes) in order to handle the
-    # padding at the end of the file
-    fp.seek(0,2)
-    filesize = fp.tell()
-    # put the file pointer back at the beginning of the file
-    fp.seek(0)
-
     # create handle for file to be decrypted
     try:
         fp = open(myInput, "rb")
@@ -433,6 +443,16 @@
             print "pyAES: unable to open output file -", filename
             sys.exit()
 
+    # recover Initialization Vector, the first block in file
+    IV = getBlock(fp)
+
+    # get the file size (bytes) in order to handle the
+    # padding at the end of the file
+    fp.seek(0,2)
+    filesize = fp.tell()
+    # put the file pointer back at the first block of ciphertext
+    fp.seek(16)
+
     # begin reading in blocks of input to decrypt
     firstRound = True
     block = getBlock(fp)