More Secrets of Cryptography

Transcript

1. More Secrets of Cryptography
   Chris Riley
   ConFoo 2018
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2. Introduction
   

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3. Why do we need cryptography?
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4. Modern cryptography
   • Confidentiality
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5. Modern cryptography
   • Confidentiality
   • Key exchange
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6. Modern cryptography
   • Confidentiality
   • Key exchange
   • Identity
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7. Modern cryptography
   • Confidentiality
   • Key exchange
   • Identity
   • Authentication
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8. Symetric vs Asymetric Cryptography
   

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9. Eliptic Curve Cryptography
   

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10. Eliptic Curve Equation
    • y2 = x3 + ax2 + b
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11. Eliptic Curve Equation
    • y2 = x3 + ax2 + b
    • y2 = x3 + 486662x2 + x
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12. An Eliptic Curve
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13. Eliptic curve dot function
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14. Eliptic curve multiplication function
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15. Eliptic curve for Cryptography
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16. Eliptic Curve Key Exchange
    • Agree a curve, modulus and generator point (G)
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17. Eliptic Curve Key Exchange
    • Agree a curve, modulus and generator point (G)
    • Select random integer d and compute P = dG
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18. Eliptic Curve Key Exchange
    • Agree a curve, modulus and generator point (G)
    • Select random integer d and compute P = dG
    • Exchange public keys (PA and PB)
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19. Eliptic Curve Key Exchange
    • Agree a curve, modulus and generator point (G)
    • Select random integer d and compute P = dG
    • Exchange public keys (PA and PB)
    • Compute a shared secret dBPA and dAPB
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20. Eliptic Curve Key Exchange
    • Agree a curve, modulus and generator point (G)
    • Select random integer d and compute P = dG
    • Exchange public keys (PA and PB)
    • Compute a shared secret dBPA and dAPB
    • Both parties have now computed dAdBG
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21. Key Exchange protocol
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22. Man in the middle
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23. The Web of Trust
    

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24. Trent, the trusted third party
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25. Can you trust a web of trust?
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26. Cryptographic Hash functions
    

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27. Ideal hash function properties
    • It should be quick and easy to compute a hash for any given
    data.
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28. Ideal hash function properties
    • It should be quick and easy to compute a hash for any given
    data.
    • It should be difficult to compute data that has a given hash.
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29. Ideal hash function properties
    • It should be quick and easy to compute a hash for any given
    data.
    • It should be difficult to compute data that has a given hash.
    • It should be unlikely that two different messages will have the
    same hash.
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30. SHA-2
    

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31. Setup phase
    • Append a single ’1’ bit to the data
    • Pad the data with ’0’ so that the data + 64 bits is a multiple
    of 512
    • Append the data length as a 64 bit integer
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32. Expansion phase
    • Split message into 512 bit blocks
    • Expand each block to 2048 bits
    • Expansion is done using shifts and rotates of the original block
    xor’d together
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33. Compression phase
    1By User:kockmeyer (Own work) CC-BY-SA-3.0, via Wikimedia Commons
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34. Merkel Trees
    

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35. A Merkel Tree
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36. A Merkel Tree
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37. Bitcoin
    

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38. What is a blockchain?
    • A Merkle tree
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39. What is a blockchain?
    • A Merkle tree
    • No central authority
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40. What is a blockchain?
    • A Merkle tree
    • No central authority
    • Multiple ’forks’ may exist
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41. What is a blockchain?
    • A Merkle tree
    • No central authority
    • Multiple ’forks’ may exist
    • There exists a consensus algorithm to determine the correct
    fork
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42. What is a blockchain?
    • A Merkle tree
    • No central authority
    • Multiple ’forks’ may exist
    • There exists a consensus algorithm to determine the correct
    fork
    • The consensus algorithm only requires data contained on the
    blockchain to run
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43. Mining a bitcoin
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44. Why do bitcoins have value?
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45. Should I use a block chain for ... ?
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46. Thanks
    • @giveupalready
    • https://github.com/carnage
    • https://carnage.github.io
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