Cracking the DES Encryption

Outline DES Encryption (in general). DES Vulnerabilities. Cracking the DES (DESCHALL). Using Condor Advantages.

DES Encryption In general

History In 1971, LUCIFER algorithm was developed. Cyphers block of 64 bits, using a 128-bit key LUCIFER was refined by IBM researchers. The key was reduced to 56-bit: fits on a chip. In 1977, the IBM project was adopted as the Data Encryption Standard (DES) by NSA.

Encryption Basics – Symmetric Key Encryption Plaintext DEAD 1101 1110 1010 1101 Key BEEF 1011 1110 1110 1111 Ciphertext 0110 0000 0100 0010 = 6042  = Plaintext 1101 1110 1010 1101 = DEAD Ciphertext 6042 0110 0000 0100 0010 Real Simple: Same key to encode and decode Encoding and Decoding algorithms are symmetrical!

DES Algorithm Crypts 64 bits blocks of plain text. Using a 56 bits key. Expands the Symmetric Key Encryption 16 stages of processing Block Ciphers. Initial & Final Permutations (IP, FP) Using Feistel Function & Key Schedule

48 bit subkey Generator Ki(48) = g(i,K(56)) (The key for each round is Li-1 Ri-1 Li Ri 48 bit subkey Generator Ki(48) = g(i,K(56)) (The key for each round is deterministically found from the input 56 bit key). Expansion Permutation S-Box Substitution P-Box Permutation 32 48                         ,                                                                                                                                                        .

IP – Initial Permutation 8 16 24 32 40 48 56 FP – Final Permutation 8 16 24 32 40 48 56

DES Advantages Strong encryption-Confusion and diffusion Using a non linear function (S-Box) Using bit permutation (P-Box) Ideally suited for implementation in hardware (bit shifts, look-ups etc). Suited for video & voice.

DES Vulnerabilities  Are there any disadvantages?

Brute Force Attack Basic attack for deciphering any kind of encrypted data. Trying all possible options. Takes a lot of time and resources. Dedicated hardware is faster than software.

56 bit Key - Advantage or Disadvantage? 256 possible keys = 72,057,594,037,927,936 Moore’s law compatible. Even 20 years later(1997), it would take: 2,285 years to decipher! With a 200 MHz Pentium system that can test approximately 1 million keys/second.

More Efficient Exploitations Differential cryptanalysis Linear cryptanalysis Both require hundreds of Terabytes of cyphered & deciphered messages. Still requires 2^43 iterations. Dedicated machines.

DESCHALL Competition Cracking the algorithm – it’s all about the money

The Challenge RSA Security offered a 10,000$ prize in 1997, for the first who crack the DES. A group of computer scientists involved thousands of volunteers deciphered it! It took only 96 days! (against 2,285 years) How did they manage to get a speedup of 8687 ??? How come the DES developers didn’t see it coming?

The Solution There was no internet when DES was introduced in 1977. Even in 1997 the internet sounded bad. Parallel Computing is the answer! Simply using brute force. With the help of up to 14k computers a day and a total of 78k unique computers. By offering a 4,000$ prize to the computer owner who finds the right key.

DESCHALL Competition How does it works?

Client Flowchart Server Flowchart

Calculation Speed Average user speed is a sine form Computers are more idle on weekends.

Growing popularity. Parabolic growth of total calculated keys. Only ¼ of all key options was needed to be calculate.

Can HTCondor Help? Parallel computing using High Throughput Computing (HTC)

Condor Relevant Advantages Sequential execution of a series of programs without human interaction. Supports many different machines. High throughput computing. Open source and easy to setup.

Conclusions DES was outdated after DESCHALL. Nowadays internet can help us achieve tremendous computing power with the growing amount of computers connected. Longer keys are better - 256 bit key is common and believed to be hard to brute force (78 digits!) Better encryption methods are in use today but they are also vulnerable!

Referances http://lasecwww.epfl.ch/memo/memo_des.shtml http://www.interhack.net/projects/deschall/ http://www.interhack.net/pubs/des-key-crack/ http://linuxgazette.net/issue46/serrao.html http://www.distributed.net/DES http://en.wikipedia.org/wiki/DESCHALL_Project http://en.wikipedia.org/wiki/Data_Encryption_Standard http://en.wikipedia.org/wiki/Brute_force_attack http://www.worldofhacker.com/2013/09/basic-idea-of-creating-password.html http://www.hep.uiuc.edu/home/mats/crypto/crypto.ppt