diff -Naur pyPdf-1.12/pyPdf/generic.py src/pyPdf-1.12/pyPdf/generic.py
--- pyPdf-1.12/pyPdf/generic.py	2009-08-03 19:11:12.000000000 +0200
+++ pyPdf-1.12/pyPdf/generic.py	2009-08-03 20:40:22.000000000 +0200
@@ -212,8 +212,6 @@
 
 
 class NumberObject(int, PdfObject):
-    def __init__(self, value):
-        int.__init__(self, value)
 
     def writeToStream(self, stream, encryption_key):
         stream.write(repr(self))
@@ -402,9 +400,6 @@
 class NameObject(str, PdfObject):
     delimiterCharacters = "(", ")", "<", ">", "[", "]", "{", "}", "/", "%"
 
-    def __init__(self, data):
-        str.__init__(self, data)
-
     def writeToStream(self, stream, encryption_key):
         stream.write(self)
 
diff -Naur pyPdf-1.12/pyPdf/pdf.py src/pyPdf-1.12/pyPdf/pdf.py
--- pyPdf-1.12/pyPdf/pdf.py	2008-09-02 23:19:48.000000000 +0200
+++ pyPdf-1.12/pyPdf/pdf.py.fixed	2009-11-11 13:28:03.000000000 +0100
@@ -49,7 +49,6 @@
 import warnings
 from generic import *
 from utils import readNonWhitespace, readUntilWhitespace, ConvertFunctionsToVirtualList
-from sets import ImmutableSet
 
 ##
 # This class supports writing PDF files out, given pages produced by another
@@ -119,7 +118,7 @@
     # encryption.  When false, 40bit encryption will be used.  By default, this
     # flag is on.
     def encrypt(self, user_pwd, owner_pwd = None, use_128bit = True):
-        import md5, time, random
+        import hashlib, time, random
         if owner_pwd == None:
             owner_pwd = user_pwd
         if use_128bit:
@@ -133,8 +132,8 @@
         # permit everything:
         P = -1
         O = ByteStringObject(_alg33(owner_pwd, user_pwd, rev, keylen))
-        ID_1 = md5.new(repr(time.time())).digest()
-        ID_2 = md5.new(repr(random.random())).digest()
+        ID_1 = hashlib.md5(repr(time.time())).digest()
+        ID_2 = hashlib.md5(repr(random.random())).digest()
         self._ID = ArrayObject((ByteStringObject(ID_1), ByteStringObject(ID_2)))
         if rev == 2:
             U, key = _alg34(user_pwd, O, P, ID_1)
@@ -160,7 +159,7 @@
     # @param stream An object to write the file to.  The object must support
     # the write method, and the tell method, similar to a file object.
     def write(self, stream):
-        import struct, md5
+        import struct, hashlib
 
         externalReferenceMap = {}
         self.stack = []
@@ -181,7 +180,7 @@
                 pack2 = struct.pack("<i", 0)[:2]
                 key = self._encrypt_key + pack1 + pack2
                 assert len(key) == (len(self._encrypt_key) + 5)
-                md5_hash = md5.new(key).digest()
+                md5_hash = hashlib.md5(key).digest()
                 key = md5_hash[:min(16, len(self._encrypt_key) + 5)]
             obj.writeToStream(stream, key)
             stream.write("\nendobj\n")
@@ -554,12 +553,12 @@
             if not hasattr(self, '_decryption_key'):
                 raise Exception, "file has not been decrypted"
             # otherwise, decrypt here...
-            import struct, md5
+            import struct, hashlib
             pack1 = struct.pack("<i", indirectReference.idnum)[:3]
             pack2 = struct.pack("<i", indirectReference.generation)[:2]
             key = self._decryption_key + pack1 + pack2
             assert len(key) == (len(self._decryption_key) + 5)
-            md5_hash = md5.new(key).digest()
+            md5_hash = hashlib.md5(key).digest()
             key = md5_hash[:min(16, len(self._decryption_key) + 5)]
             retval = self._decryptObject(retval, key)
 
@@ -986,8 +985,8 @@
 
         # Combine /ProcSet sets.
         newResources[NameObject("/ProcSet")] = ArrayObject(
-            ImmutableSet(originalResources.get("/ProcSet", ArrayObject()).getObject()).union(
-                ImmutableSet(page2Resources.get("/ProcSet", ArrayObject()).getObject())
+            frozenset(originalResources.get("/ProcSet", ArrayObject()).getObject()).union(
+                frozenset(page2Resources.get("/ProcSet", ArrayObject()).getObject())
             )
         )
 
@@ -1369,18 +1368,24 @@
     password = (password + _encryption_padding)[:32]
     # 2. Initialize the MD5 hash function and pass the result of step 1 as
     # input to this function.
-    import md5, struct
-    m = md5.new(password)
+    import hashlib, struct
+    m = hashlib.md5(password)
     # 3. Pass the value of the encryption dictionary's /O entry to the MD5 hash
     # function.
-    m.update(owner_entry)
+    if isinstance(owner_entry, str):
+        m.update(owner_entry.original_bytes)
+    else:
+        m.update(owner_entry.original_bytes)
     # 4. Treat the value of the /P entry as an unsigned 4-byte integer and pass
     # these bytes to the MD5 hash function, low-order byte first.
     p_entry = struct.pack('<i', p_entry)
     m.update(p_entry)
     # 5. Pass the first element of the file's file identifier array to the MD5
     # hash function.
-    m.update(id1_entry)
+    if isinstance(id1_entry, str):
+        m.update(id1_entry)
+    else:
+        m.update(id1_entry.original_bytes)
     # 6. (Revision 3 or greater) If document metadata is not being encrypted,
     # pass 4 bytes with the value 0xFFFFFFFF to the MD5 hash function.
     if rev >= 3 and not metadata_encrypt:
@@ -1394,7 +1399,7 @@
     # /Length entry.
     if rev >= 3:
         for i in range(50):
-            md5_hash = md5.new(md5_hash[:keylen]).digest()
+            md5_hash = hashlib.md5(md5_hash[:keylen]).digest()
     # 9. Set the encryption key to the first n bytes of the output from the
     # final MD5 hash, where n is always 5 for revision 2 but, for revision 3 or
     # greater, depends on the value of the encryption dictionary's /Length
@@ -1436,14 +1441,14 @@
     password = (password + _encryption_padding)[:32]
     # 2. Initialize the MD5 hash function and pass the result of step 1 as
     # input to this function.
-    import md5
-    m = md5.new(password)
+    import hashlib
+    m = hashlib.md5(password)
     # 3. (Revision 3 or greater) Do the following 50 times: Take the output
     # from the previous MD5 hash and pass it as input into a new MD5 hash.
     md5_hash = m.digest()
     if rev >= 3:
         for i in range(50):
-            md5_hash = md5.new(md5_hash).digest()
+            md5_hash = hashlib.md5(md5_hash).digest()
     # 4. Create an RC4 encryption key using the first n bytes of the output
     # from the final MD5 hash, where n is always 5 for revision 2 but, for
     # revision 3 or greater, depends on the value of the encryption
@@ -1473,14 +1478,17 @@
     key = _alg32(password, rev, keylen, owner_entry, p_entry, id1_entry)
     # 2. Initialize the MD5 hash function and pass the 32-byte padding string
     # shown in step 1 of Algorithm 3.2 as input to this function. 
-    import md5
-    m = md5.new()
+    import hashlib
+    m = hashlib.md5()
     m.update(_encryption_padding)
     # 3. Pass the first element of the file's file identifier array (the value
     # of the ID entry in the document's trailer dictionary; see Table 3.13 on
     # page 73) to the hash function and finish the hash.  (See implementation
     # note 25 in Appendix H.) 
-    m.update(id1_entry)
+    if isinstance(id1_entry, str):
+        m.update(id1_entry)
+    else:
+        m.update(id1_entry.original_bytes)
     md5_hash = m.digest()
     # 4. Encrypt the 16-byte result of the hash, using an RC4 encryption
     # function with the encryption key from step 1.