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Eugene Vasserman cis.ksu/~eyv/CIS755_S14/

Class 4 Asymmetric Cryptography and Trusting Internal Components CIS 755: Advanced Computer Security Spring 2014. Eugene Vasserman http://www.cis.ksu.edu/~eyv/CIS755_S14/. Administrative stuff. Quiz on Thursday Cryptography concepts Examples… Project due dates posted

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Eugene Vasserman cis.ksu/~eyv/CIS755_S14/

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  1. Class 4Asymmetric Cryptography and Trusting Internal Components CIS 755: Advanced Computer SecuritySpring 2014 Eugene Vasserman http://www.cis.ksu.edu/~eyv/CIS755_S14/

  2. Administrative stuff • Quiz on Thursday • Cryptography concepts • Examples… • Project due dates posted • Schedule always being updated – watch for changes • What would you like to see covered? • Paper reading and the “huh?” moment

  3. Last time: Basic primitives • Confidentiality (encryption) • Symmetric (e.g. AES) • Asymmetric (e.g. RSA) • Hash functions • Integrity and authentication • Symmetric (authentication codes) • Asymmetric (signatures) • Random numbers

  4. Asymmetric cryptography • The idea: base security properties on mathematical statements • Facts or assumptions • We need to be familiar with our toolset • NEVER BUILD YOUR OWN WHEN SOLUTION EXISTS!!

  5. NEVER BUILD YOUR OWN WHEN SOLUTION EXISTS!!!

  6. Asymmetric • No pre-shared keys • Public and secret keys (key pairs) • Asymmetric means…? • Non-repudiable • Key agreement, e.g. Diffie-Hellman • Not like sending password in the clear • Mathematical proof based on conjecture • Variants of conjecture (important)

  7. Security (strength) • Key size* • Commonly 2256 for AES, 22048 for RSA • What is a [good] key? • Underlying cryptosystem/primitives • Composition • e.g. MAC with broken underlying hash function may not itself be broken

  8. Current state of symmetric encryption • DES is too weak (56-bit key) • 3DES is weak (168-bit keys but only 2112 security – “meet-in-the-middle” attack) • Recent weaknesses in AES: • AES-256 (2254.4) AES-192 (2189.7) AES-128 (2126.1) http://research.microsoft.com/en-us/projects/cryptanalysis/aesbc.pdf

  9. Current state of hash functions • MD5 is broken • http://www.win.tue.nl/hashclash/ • SHA-1 is known to be weak • http://theory.csail.mit.edu/~yiqun/shanote.pdf (269) • http://eprint.iacr.org/2004/304 (2106, generalizable) • SHA-256 (variant) is even weaker • SHA-3 currently in “development” (NIST) • We have a winner: all hail Keccak (SHA-3)! • http://csrc.nist.gov/groups/ST/hash/sha-3/

  10. Questions? Trusted component discussion

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