Another WWII Message Decoded
It’s a really interesting code and story. (The first link has the most detailed information about the code and the cryptanalysis.)
Entries Tagged "cryptography"
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NSA Cryptography Course
This article, from some internal NSA publication, is about Lambros Callimahos, who taught an intensive 18-week course on cryptology for many years and died in 1977. Be sure to notice the great redacted photo of him and his students on page 17.
Last Battle-of-Midway Cryptanalyst
The last cryptanalyst at the Battle of Midway, Rear Admiral Donald “Mac” Showers, USN-Ret, passed away 19 October 2012. His interment at Arlington National Cemetery at Arlington, Virginia, will be Monday, April 15, at 3:00. The family made this a public event to celebrate his life and contributions to the cryptologic community.
Nice Security Mindset Example
A real-world one-way function:
Alice and Bob procure the same edition of the white pages book for a particular town, say Cambridge. For each letter Alice wants to encrypt, she finds a person in the book whose last name starts with this letter and uses his/her phone number as the encryption of that letter.
To decrypt the message Bob has to read through the whole book to find all the numbers.
And a way to break it:
I still use this example, with an assumption that there is no reverse look-up. I recently taught it to my AMSA students. And one of my 8th graders said, “If I were Bob, I would just call all the phone numbers and ask their last names.”
In the fifteen years since I’ve been using this example, this idea never occurred to me. I am very shy so it would never enter my mind to call a stranger and ask for their last name. My student made me realize that my own personality affected my mathematical inventiveness.
I’ve written about the security mindset in the past, and this is a great example of it.
Apple's iMessage Encryption Seems to Be Pretty Good
The U.S. Drug Enforcement Agency has complained (in a classified report, not publicly) that Apple’s iMessage end-to-end encryption scheme can’t be broken. On the one hand, I’m not surprised; end-to-end encryption of a messaging system is a fairly easy cryptographic problem, and it should be unbreakable. On the other hand, it’s nice to have some confirmation that Apple is looking out for the users’ best interests and not the governments’.
Still, it’s impossible for us to know if iMessage encryption is actually secure. It’s certainly possible that Apple messed up somewhere, and since we have no idea how their encryption actually works, we can’t verify its functionality. It would be really nice if Apple would release the specifications of iMessage security.
EDITED TO ADD (4/8): There’s more to this story:
The DEA memo simply observes that, because iMessages are encrypted and sent via the Internet through Apple’s servers, a conventional wiretap installed at the cellular carrier’s facility isn’t going to catch those iMessages along with conventional text messages. Which shouldn’t exactly be surprising: A search of your postal mail isn’t going to capture your phone calls either; they’re just different communications channels. But the CNET article strongly implies that this means encrypted iMessages cannot be accessed by law enforcement at all. That is almost certainly false.
The question is whether iMessage uses true end-to-end encryption, or whether Apple has copies of the keys.
Another article.
Skein Collision Competition
Xkcd had a Skein collision competition. The contest is over—Carnegie Mellon University won, with 384 (out of 1024) mismatched bits—but it’s explained here.
New RC4 Attack
This is a really clever attack on the RC4 encryption algorithm as used in TLS.
We have found a new attack against TLS that allows an attacker to recover a limited amount of plaintext from a TLS connection when RC4 encryption is used. The attacks arise from statistical flaws in the keystream generated by the RC4 algorithm which become apparent in TLS ciphertexts when the same plaintext is repeatedly encrypted at a fixed location across many TLS sessions.
The attack is very specialized:
The attack is a multi-session attack, which means that we require a target plaintext to be repeatedly sent in the same position in the plaintext stream in multiple TLS sessions. The attack currently only targets the first 256 bytes of the plaintext stream in sessions. Since the first 36 bytes of plaintext are formed from an unpredictable Finished message when SHA-1 is the selected hashing algorithm in the TLS Record Protocol, these first 36 bytes cannot be recovered. This means that the attack can recover 220 bytes of TLS-encrypted plaintext.
The number of sessions needed to reliably recover these plaintext bytes is around 230, but already with only 224 sessions, certain bytes can be recovered reliably.
Is this a big deal? Yes and no. The attack requires the identical plaintext to be repeatedly encrypted. Normally, this would make for an impractical attack in the real world, but http messages often have stylized headers that are identical across a conversation—for example, cookies. On the other hand, those are the only bits that can be decrypted. Currently, this attack is pretty raw and unoptimized—so it’s likely to become faster and better.
There’s no reason to panic here. But let’s start to move away from RC4 to something like AES.
Really Clever TLS Attack
This is an extremely clever man-in-the-middle timing attack against TLS that exploits the interaction between how the protocol implements AES in CBC mode for encryption, and HMAC-SHA1 for authentication. (And this is a really good plain-language description of it.)
Breaking Hard-Disk Encryption
The newly announced ElcomSoft Forensic Disk Decryptor can decrypt BitLocker, PGP, and TrueCrypt. And it’s only $300. How does it work?
Elcomsoft Forensic Disk Decryptor acquires the necessary decryption keys by analyzing memory dumps and/or hibernation files obtained from the target PC. You’ll thus need to get a memory dump from a running PC (locked or unlocked) with encrypted volumes mounted, via a standard forensic product or via a FireWire attack. Alternatively, decryption keys can also be derived from hibernation files if a target PC is turned off.
This isn’t new. I wrote about AccessData doing the same thing in 2007:
Even so, none of this might actually matter. AccessData sells another program, Forensic Toolkit, that, among other things, scans a hard drive for every printable character string. It looks in documents, in the Registry, in e-mail, in swap files, in deleted space on the hard drive … everywhere. And it creates a dictionary from that, and feeds it into PRTK.
And PRTK breaks more than 50 percent of passwords from this dictionary alone.
It’s getting harder and harder to maintain good file security.
Comedy and Cryptography
Not the sort of pairing I normally think of, but:
Robin Ince and Brian Cox are joined on stage by comedian Dave Gorman, author and Enigma Machine owner Simon Singh and Bletchley Park enthusiast Dr Sue Black as they discuss secret science, code-breaking and the extraordinary achievements of the team working at Bletchley during WW II.
Audio here.
Sidebar photo of Bruce Schneier by Joe MacInnis.