Parallel Algorithm Leads To Crypto Breakthrough

Hugh Pickens writes "Dr. Dobbs reports that a cracking algorithm using brute force methods can analyze the entire DES 56-bit keyspace with a throughput of over 280 billion keys per second, the highest-known benchmark speeds for 56-bit DES decryption and can accomplish a key recovery that would take years to perform on a PC, even with GPU acceleration, in less than three days using a single, hardware-accelerated server with a cluster of 176 FPGAs. The massively parallel algorithm iteratively decrypts fixed-size blocks of data to find keys that decrypt into ASCII numbers. Candidate keys that are found in this way can then be more thoroughly tested to determine which candidate key is correct." Update by timothy, 2010-01-29 19:05 GMT: Reader Stefan Baumgart writes to point out prior brute-force methods using reprogrammable chips, including Copacobana (PDF), have achieved even shorter cracking times for DES-56. See also this 2005 book review of Brute Force, about the EFF's distributed DES-breaking effort that succeeded in 1997 in cracking a DES-encrypted message. "'This DES cracking algorithm demonstrates a practical, scalable approach to accelerated cryptography,' says David Hulton, an expert in code cracking and cryptography. 'Previous methods of acceleration using clustered CPUs show increasingly poor results due to non-linear power consumption and escalating system costs as more CPUs are added. Using FPGAs allows us to devote exactly the amount of silicon resources needed to meet performance and cost goals, without incurring significant parallel processing overhead.' Although 56-bit DES is now considered obsolete, having been replaced by newer and more secure Advanced Encryption Standard (AES) encryption methods, DES continues to serve an important role in cryptographic research, and in the development and auditing of current and future block-based encryption algorithms."

Comments

How do you know when it's decrypted?

[petes_PoV]

Apart form the trivial case where some ASCII, or a picture pops up, how can a decrypter know when the block or stream of apparently random data has been decrypted?

If I was to start transmitting some random data and told people it was encrypted with DES 56 bit, but in fact it wasn't - it was just random data. Then, apart from exhaustively testing it with every possible key, how could they demonstrate that it was NOT encrypted as claimed?
It does seem to me that one of the problems with decrypting "stuff" is that you need to have some idea what the "answer" will look like. Without that you can't ever be certain when you've succeeded.

Re:How do you know when it's decrypted?

[Anonymous Coward]

Depending on the cipher, this may, or may not work.

A common method to enhance the security of DES is/was to do a encrypt/"decrypt"/encrypt cycle, each with a different key. You may know this method under the name of 3DES. While DES is long broken, 3DES is still considered pretty secure, albeit slow. In contrast, using "tripple-XOR" will most likely not increase the security of a cipher.

And encrypting multiple time with the same key will, for any reasonably secure crypto system*, not increase security. The security incerase in 3DES was due to the increased key length (i.e. the combined length of the 3 keys used in 3DES). Using the same key over and over again does not increase the effective key length.

*Increasing the number of rounds used internally in a crypto system can in some cases increase the security. Usually, cryptoanalists start breaking reduced-rounds versions of ciphers before breaking the full version.

What a load of crap!

[ladadadada]

There has been no "crypto breakthrough".

What they have done is created a chip that can do 1.6 billion DES operations per second (compared to 250 million for a GPU card) and then put 176 of them in a 4U server. This lowers the price to performance ratio by around a factor of 6 if you assume that their chip and a GPU are the same price.. By the way, this press release (and research) was made by the company that manufactures the chips in question.

The "massively parallel" algorithm (their term, Dr. Dobbs just copied it) only decrypts a little of the file and looks for ASCII integers because that's what they put in the file before encrypting it. They have not found a way of culling candidate keys without already knowing what sort of data is in the encrypted file. That would be a "crypto breakthrough".

it's a good bit of technology with many uses beyond cryptography that has, unfortunately, been marred by some overly breathless reporting.