COPACOBANA: RECONFIGURABLE COMPUTING IN CRYPTANALYSIS. Ben Johnstone

Transcription

1 COPACOBANA: RECONFIGURABLE COMPUTING IN CRYPTANALYSIS Ben Johnstone

2 Overview Goals Architecture DES Performance Conclusion

3 What is COPACOBANA? Cost Optimized Parallel Code Breaker

4 History Developed at the Universities of Bochum and Kiel in Germany Breaks DES in 9 days Later improved to ~6 days

5 Goals Two main objectives: 1. Optimum cost-performance ratio 2. Flexibility due to reprogrammabilty

6 Architecture Reconfigurable Uses Xilinx Spartan Parallel 120 FPGA chips Controller board Optimized cost-performance ratio COTS hardware

7 Internal View

8 Motivation for RC Supercomputers Fast, powerful, easy to program Expensive, bad cost-performance ratio Distributed systems may have privacy issues i.e. Boinc: Using other user s idle PCs Reconfigurable Flexible compared to ASICS

9 Applications Optimized for cryptanalysis Main application: DES key search Can also crack 1-time password systems Attack primitive systems epass: machine readable passports Norton Diskreet: hard drive encryption Security Estimations Aids other attacks Parallelized Elliptic Curve Method (ECM)

10 DES Symmetric block cipher Encryption standard set in 1976 Remained a popular standard for several decades Weaknesses: Short key length (56-bits) Susceptible to differential, linear cryptanalysis 2002 AES effective

11 Cryptanalysis Encryption: Ek(P) -> Ciphertext Goal: Get the preimage (plaintext) Little knowledge of plaintext beforehand Requires the key Known-plaintext Use a preexisting plaintext block found in the ciphertext

12 Methods Brute force Try every key until something works 56-bit key -> 2^56 or 72,057,594,037,927,936 keys Differential cryptanalysis Observe how different inputs affect the output Linear cryptanalysis

13 DES Exhaustive Key Search

14 Performance Per FPGA: 4 keys per cycle 400 million keys per 100MHz Total: 120 FPGAs -> 4.8E10 keys per second On average check 2^55 keys 750,599 seconds Average time: 6-8 days

15 Vs. GPP Pentium 4 CPU 2 million keys per 3GHz With 1 PC 2^34 seconds -> 545 years Need ~22,000 processors to match the performance of COPACOBANA

16 Vs Supercomputer 1998 Deep Crack breaks DES in 56 hours 1999 Deep Crack and distributed.net break DES in < 24 hours

17 Cost As of 2006: $10,000 Deep Crack: $250,000 Equivalent performance PC Need ~22k Pentium million Euros (2006) Power 600W

18 Limitations Brute force infeasible for bigger keys AES-128: 1.1x10^77 keys Fastest supercomputer would take 1 billion billion years More complex methods not possible with COPACOBANA alone DES is deprecated

19 Conclusion COPACOBANA delivers low-cost DES cracking capabilities Can t break modern/advanced encryption DES is mainly used in legacy systems Later work: New version developed with Virtex-4 SX 35 FPGAs RIVYERA: breaks DES in < one day

20 Questions?

21 Sources [1]Arora, Mohit. Nov design/ /how-secure-is-aes-against-brute-force-attacks- [2] COPACOBANA S Nov [3] COPACOBANA: A Codebreaker for DES and other Ciphers. 2 Nov [4] Data Encryption Standard. 2 Nov [5] Howson, Ian. A Cost/Performance Study of Modern FPGAs in Cryptanalysis. [6] Pelzl, Jan. 4 Dec Cryptanalysis With a Cost-Optimized FPGA Cluster. [7] S. Kumar et. al. 10 Oct Breaking Ciphers with COPACOBANA A Cost-Optimized Parallel Code Breaker or How to Break DES for 8,980 [8] Tim Erhan Guneysu. Feb Cryptography and Cryptanalysis on Reconfigurable Devices: Security Implementations for Hardware and Reprogrammable Devices.

22 Pictures tandard_infobox_diagram.png/300px- Data_Encryption_Standard_InfoBox_Diagram.png guide.com/photos/stock_photos/intel%20pentium%204%20%20lga775.jpg Key search layout and Deep Crack image taken from [6]