Re: Encryption
Re: Encryption
- Subject: Re: Encryption
- From: Shawn Erickson <email@hidden>
- Date: Fri, 2 Jan 2004 08:50:00 -0800
On Jan 1, 2004, at 6:44 PM, Shawn Erickson wrote:
On Jan 1, 2004, at 6:08 PM, Robert Tito wrote:
Hi Shawn
If I get my hand on an encrypted (by a standard single engine)
document it
takes aboutt 15-20 minutes to crack it.
It takes some more time to tackle a 512 bits document but then the
problem
lies within the single engine: they are all well known and described.
I may not be following the above fully but...
Are saying that you can tell me the original (ASCII) text message in
the enclosed file that was encrypted using AES with a 128b key?
[7%Zb+)G@Oe]UiIM mr4tc`4pXE"1`hZ wA@ ^tSF
Note I used Apple sample CryptTool [1] to generate the encrypted file.
-Shawn
[1]
http://developer.apple.com/samplecode/Sample_Code/Security/
CryptoSample.htm
Oops, I forgot the list drops attachments. So the following is the
encrypted file base64 encoded and inlined in the message.
WzcZpVpiqylHQM9lXdWS6clNIO3yFDQGdONgtPDYxSKWsQdg6Nodd0GEwIne9FNG
Anyway I believe either Robert is talking about some type of far
weaker, for the number of bits, encryption or is talking about
attacking the fact that humans often provide the seeds (aka passwords)
that are used to generate the final keys used by the cypher. Humans
often pick passwords that are easy to crack with dictionary attacks
(use of common words, key patterns, anagrams, etc.) and/or they pick
passwords that are themselves far shorter then the desired key size (8
or so characters instead of the 16 or more you often need for 128b
keys) which have a way of greatly reducing the "key" space to something
that can be cracked in a relatively short order.
In the case of the above encrypted message I used a pseudo random
(rather poor random at that) password of 34 characters (I meant to use
32 oh well...). So a dictionary attack will be hard because of the
randomness of the password and the number of possible passwords 34
characters in length (using only alphanumerics) is 8.2x10^52 (which is
larger then the 128b key space used) so brute forcing that would be
harder then attacking the possible cypher keys. At least based on my
rather limited knowledge of things... :-)
-Shawn
p.s. Robert got back to me saying that he didn't want to attempt it at
4 AM his time which I fully understand, hopefully he can find the time
later, I would truly like to know if it is possible and if so how.
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