Undeterred by Blu-ray hacks, Sony unveils yet another cipher for DRM

26th Mar 2007 07:49 #1

Member

Sony announced late last week that they have invented a new encryption mechanism known as "CLEFIA," a block cipher algorithm designed to help content producers deliver "advanced copy protection" with their products. The name comes from a play on the French word clef, which means "key." We can't help but snicker, given that it has been key-sniffing that has been undoing DRM as of late.

CLEFIA is aimed at portable electronics and home entertainment products, and can be applied to music, images, or even video. The big claim from Sony is that CLEFIA has "sufficient immunity against known cryptanalytic attacks," yet it has relatively low hardware requirements. The company plans to formally present the CLEFIA algorithm at the Fast Software Encryption 2007 conference in Luxembourg.

Sony claims that the new algorithm is extremely efficient; when implemented in hardware, it can achieve a maximum throughput of 1.42 Gbps using a 0.09 micrometer CMOS standard cell library and gate size of 6.1K, which Sony says is a new record for hardware gate efficiency.

The idea is to make it possible to implement the protection as a relatively inexpensive hardware component for media playback devices. Software implementations are also possible, and Sony claims that they will achieve "high speed performance on a wide variety of processors," although the company declined to give specific figures.

Block ciphers are a common cryptographic tool used in many existing algorithms, including the US government encryption standard DES—a variant of which has been used to serve secure web pages—and its replacement, AES. Unlike simple ciphers that translate a character at a time, block ciphers encrypt entire blocks of text at once, using a secret key which can be of varying lengths. CLEFIA uses a block size of 128 bits, and can be configured to use keys of 128, 192, or 256 bits.

Theory versus praxis

So are Sony's claims of the cipher being "immune" to attacks real or just marketing? Block ciphers can be made resistant against garden variety brute-force attacks simply by using longer key lengths. The length of the key required to prevent these attacks continues to increase as CPUs get faster—key lengths of 80 bits were once considered completely secure, but today 128 bit keys are commonly used by applications such as web browsers for SSL.

Yet brute-force is rarely the method by which DRM schemes are cracked. Most approaches attempt to capture the keys directly, either by scanning a computer's memory while it is playing back the movie with a software player, or capturing it while it is transit from the optical drive to the computer by sniffing the data going through a USB cable. The AACS copy protection used on Blu-ray and HD DVD discs, for example, has already been broken in this way, although the specification anticipated this occurring and allows for compromised keys to be revoked at a future date.

CLEFIA will not magically make future content protection "unhackable," although it may make it cheaper to add copy protection to more types of devices, which is really what Sony is going for here.

26th Mar 2007 08:59 #2

Bullworth

Member

Notice how Sony plans on making it cheaper and admit that it is not hacker-proof. Sounds like another money making scheme.

You can fool some people all the time,you can fool some people part of the time, but you can't fool everybody all the time

26th Mar 2007 09:06 #3

oldandinthe way

Member

In the background we must remember that any cipher marketed in the US must be crackable by the NSA.

If the NSA can crack it NOW, hackers can crack it in time.

Back in the 60's when DES was designed, it was assumed that only the NSA, the KGB and the Mafia had sufficient computer power to crack it. Now just about anyone has enough.

Announcements like this are designed to show a commitment to encryption, and a market opportunity, not a dramatic breakthrough.

26th Mar 2007 09:39 #4

thecoalman

Member

Originally Posted by oldandinthe way

In the background we must remember that any cipher marketed in the US must be crackable by the NSA.

Has to be? Can't say i ever heard that and can't find any reference to it. If that was the case they might as well just give them a backdoor...