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Cryptanalysis on FPGA Based Hardware Malcolm Alda Sumantri Bachelors of Engineering (Software) & Bachelors of Commerce (Finance) Supervisors: Matt Barrie Craig Jin The University of Sydney Introduction Welcome to the Digital Age where everything can be replicated! Cryptography is used…

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cryptanalysis on fpga based hardware

Cryptanalysis on FPGA Based Hardware

Malcolm Alda SumantriBachelors of Engineering (Software) & Bachelors of Commerce (Finance)

Supervisors:Matt BarrieCraig Jin

The University of Sydney

  • Welcome to the Digital Age where everything can be replicated!
  • Cryptography is used…
    • To protect our privacy
      • For example: our real identity, our e-mails to family and friends, our digital photos, our work.
    • To protect corporate secrets
      • For example: future corporate strategies, intellectual property, pricing information, human resources information.
    • Bygovernments
      • For example: sending messages to spies, task forces, between agencies to protect civilians and against terrorism.
  • How secure are our currently deployed cryptosystems?
  • Information security is a resource game.
    • More funds means more access to information.
      • The US National Security Agency’s annual budget is classified but is said to be over US $13 billion.
      • Assessing the strength of our cryptosystems therefore involves determining the cost to break them.
  • Rapid development in Field Programmable Gate Array Technology (FPGA) technology that makes it cheaper to develop high-performance custom hardware systems. FPGA technology has proven to be effective for cryptographic use.
  • A recent optimization in cryptanalysis.
    • Rainbow Tables
  • Symmetric Cipher
  • Cryptanalysis: Code breaking, reveal the plaintext without the key.
    • Exhaustive Key Search: Try every key possible, requires large computational power.
    • Table Lookup: Store keys and ciphertexts in a massive tables to perform a lookup when trying to attack, requires a large amount of memory (infeasible).
    • Time-memory trade-off: Give up memory to achieve a faster attack time.
  • FPGAs
    • Reconfigurable logic (upload the bitstream to the hardware).
    • Cheaper than Application Specific Integrated Circuits (ASICs) for small volumes.
time memory trade off rainbow tables
Time-Memory Trade-Off:Rainbow Tables
  • How does it work?
    • Assume a chosen-plaintext attack scenario.
      • The attacker can choose which plaintext to access.
      • This attacker will use this to attack the cryptosystem.
      • This is practical in the real-world (UNIX password hashing, “#include <stdio.h>”, “\n”)
    • Two Phases
      • Precomputation Phase
      • Online Attack Phase (Cryptanalytic Attack)
  • Precomputation Phase: Generate a rainbow table.
    • A rainbow table is a two-column table (start-point, end-point)
    • These points are possible keys.
    • This table is generated by a specific algorithm.
  • Online Attack Phase: Use the rainbow table.
    • We are given a ciphertext to break.
    • Now we perform a search on the rainbow table by using another algorithm
  • This method is probabilistic, but faster than exhaustive key search.
  • Unlike exhaustive key search that only requires computational resources (processor). This method uses memory as well as computational resources.
  • As a result, the attack time is faster but we have given up memory. This is the trade-off.
  • Design and implement an FPGA based cryptanalytic system that uses the rainbow tables method of cryptanalysis.
  • Use the Data Encryption Standard (DES) as the test symmetric cipher.
    • DES uses a 56-bit key.
    • DES is the most widely studied cipher.
    • DES is still used today (UNIX password hashing).
  • Determine the cost to break DES.
  • Extrapolate the cost to break other ciphers.

Design I – Data Encryption Standard

  • In designing a cryptanalytic system, the performance of the cipher module will determine the performance.
  • Security of DES derives from 16 rounds of permutations, substitutions and xoring.
  • Each round is implemented as a 3-stage pipeline. A total of 48-stages for the 16 rounds of DES.
    • Pipelining improves performance:
      • Attain higher clock frequencies.
      • Achieve parallelization: 48 encryptions per clock cycle.
design ii the rainbow table precomputation system
Design II – The Rainbow Table Precomputation System

1. High Level System Design

2. Hardware Design

3. Hardware output behavior (Timing Diagram)

design iii the rainbow table online attack system
Design III – The Rainbow Table Online Attack System

1. High Level System Design

2. Hardware Design

3. Mechanism

experiment and results
Experiment and Results
  • Experiment:
    • Cryptanalytic attack on 40-bit DES since the resources to break DES is out-of-reach for the budget in this thesis.
    • Use Sensory NetworksTM NodalCoreTM C-1000 PCI Card.
      • Xilinx® Virtex-II Pro VP-40 FPGA
      • Flexible chipset architecture to embed our hardware engines.
      • PCI interface allows for high-speed communications.
  • Results
    • 40-bit DES Rainbow Table can be generated in less than 4 hours. Table parameters allows for 85% cryptanalytic success probability.
      • Fastest known implementation in the literature based on results.
    • Online attack of 40-bit DES in 30.8 seconds.
data analysis
Data Analysis
  • Performance-Cost Analysis
    • Determine the FPGA chip that provides the highest performance for the lowest cost.
    • Synthesized the hardware designs for various Xilinx FPGAs.
    • Spartan 3 S-1500 provides the highest performance-cost relative to other Xilinx® FPGA chips.
  • Extrapolate the design of a machine to break DES (56-bit key length)
    • Result: DES can be broken with 85% success probability in 72 minutes for an approximate cost of US $1,210.

Performance-Cost of Precomputation Hardware System

  • FPGAs provides a low cost and effective solution to cryptanalysis.
  • Rainbow table attacks provide a faster attack time compared to brute-force, but brute-force uses less resources, that is, memory resources.
    • For large key sizes, the rainbow table attack becomes infeasible as memory costs is prohibitive.