## A 200 year old cipher recently broken

This Excellent article in the WSJ described the recently broken Patterson’s Cipher. Dr. Smithline from the the Center for Communications Research in Princeton, N.J., got the cipher from a neighbour working on a school project about Thomas Jefferson. Make sure to check the interactive tab on the article for a very well done graphical description of the cipher.

h/t Paul

## Secure Processors, the ultimate battlefield

Continuing with the main theme my last two posts, hacking, I am going to wrap up with this post about Secure Processors.

A secure processor is meant to protect the information and the communications, validate the communications channel and be tamper-resistant, should it falls into the adversary’s hands.

Successful hacking of secrets has the duality of being a happy/sad event, depending on which team are you playing for. The design of secure processors makes this duality patent as, in practice, the most important evaluation criterion is that the resulting product should resist the designer’s best attempts at hacking it.

The current research and development efforts are guided by U.S. DoD Anti-Tamper specifications. To prevent reverse engineering, architectures of secure processors are based on a combination of hardware and encrypted software in such a way that if the hardware is captured, its exact functions cannot be guessed without knowing the encryption keys. During WWII, the capture of an ENIGMA machine paved the way for the breaking of the enciphering by the allied forces. These historical lessons are incorporated into today’s design criteria. Some design even incorporate sensors that will detect attempts at using physical means to force the hardware and destroy the critical information upon detection (often called zeroization).

A new dimension to the problem is added by procurement system. Electronic chips are nowadays a commodity and absolute control over the manufacturing of  chips is not possible. Therefore it is essential to ensure that the critical parts, that is the processors, are designed and made in controlled facilities.

The lessons learned in military applications are now being applied to commercial system. This is where the lines blurred because in the interconnected world the enemy can wreak havoc on the infrastructure without firing a shot. Communication and control networks associated with utilities will become more resistant to attacks by using computers fitted with secure processors.

Related:

###### New Chip Brings Military Security to Commercial Processors

The Hunt for the Kill Switch

Secure Processors – IBM

Acalis White Paper

## ENIGMA encryption cracker Heroes

ENIGMA crackers reunite at Bletchley Park

I had the honour to meet one of them, now an emeritus math professor.

Check this article for pictures of the Turing Bombe the electronic-mechanical code-breaking machine used by the British to crack 3,000 Enigma messages a day during the Second World War.

Cryptool ver 1.4 has a very well done simulator of the ENIGMA machine encryption.

## Collisions, a secure hash function killer (MD5, SHA1, SHA2)

The trouble with the use of MD5 in digital signatures recently uncovered by Sotirov et al. is common to other hash functions.

NIST has been discouraging people to use MD5 and even SHA 1 since many years ago. A good account of this was posted by Dustin Trammell here.

Because the output of a hash function is of a fixed length, usually smaller that the input, there will necessarily be collisions. The collision-free property for hash is thus defined by:

A function $H$ that maps an arbitrary length message $M$ to a fixed length message digest $MD$ is a collision-free hash function if:

1. It is a one-way hash function.

2. It is hard to find two distinct messages $(M', M)$ that hash to the same result $H(M')=H(M)$.

Cryptographers talk about “relatively collision free” hash functions. A good hash function should be designed with the Avalanche Criterion in mind.

The Avalanche Criterion (AC) is used in the analysis of S-boxes or substitution boxes. S-boxes take a string as input and produce an encoded string as output.

The avalanche criterion requires that if any one bit of the input to an S-box is changed, about half of the bits that are output by the S-box should change their values. Therefore, even if collisions are unavoidable, there is no way to generate two strings with the same hash value other than brute force.