Nathaniel McHugh
June 05, 2015
8.7k

# Hack The Hash

Short 15 minute over view of hash collision attacks

June 05, 2015

## Transcript

1. ### Hack the Hash Hack the Hash / Nathaniel McHugh @natmchugh

Hash Functions http://localhost:8000/index.html?print-pdf#/ 1 of 11 05/06/15 12:10

4. ### Collisions Collisions When H(m1) = H(m2) and m1≠m2 Forge Signatures,

distribute �les di�erent behaviors, predict future not HMAC not pre-image Plenty in MD4, MD5, SHA0 None in full SHA1, SHA2 Hash Functions http://localhost:8000/index.html?print-pdf#/ 4 of 11 05/06/15 12:10
5. ### Brute Force Brute Force n ≈ √(-2 * ln(1-p) *

√d If p=0.5 then n= 1.177 * √d √365 = 19 √(2^128) = 2^64 Hash Functions http://localhost:8000/index.html?print-pdf#/ 5 of 11 05/06/15 12:10
6. ### Wang Attack Wang Attack Start with random message 1. Create

another message M’ with small di�s 2. Modify message so that certain bitwise conditions hold in intermediate state 3. Test for collision if not found go to 1 4. Hash Functions http://localhost:8000/index.html?print-pdf#/ 6 of 11 05/06/15 12:10
7. ### Δm1 = 2 , Δm2 = 2 − 2 ,

Δm12 = −2 Wang MD4 Wang MD4 M = M − M’ = (Δm0, Δm1, ......, Δm15) 31 31 28 16 Hash Functions http://localhost:8000/index.html?print-pdf#/ 7 of 11 05/06/15 12:10

9. ### Live Demo Live Demo Hash Functions http://localhost:8000/index.html?print-pdf#/ 9 of 11

05/06/15 12:10

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11. ### Collision attack in Wild Collision attack in Wild Hash Functions

http://localhost:8000/index.html?print-pdf#/ 11 of 11 05/06/15 12:10