Yes, you too can break crypto Exploiting common crypto mistakes
summary
Shows concrete exploits and working demos: a ransomware (Linux Encoder) recovers keys from predictable RNG seeded by file time; RC4 reuse xors two ciphertexts to reveal images; ECB leaks image structure while CBC with a random IV hides it; using the key as IV yields a recoverable key via block manipulation; live padding oracle exploit decrypts bytes by probing responses; stream cipher bit‑flipping turns "guest" into "admin"; password hashing comparisons use John the Ripper (100k/s vs ~44/s for PBKDF2); code and demos are on GitHub.
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chapters (22)
- 0:00Intro
- 1:47Why this talk • Cryptography: HARD
- 2:50whoami • Past: software development
- 3:54General recommendations
- 5:15Common mistakes
- 7:19Exclusive OR (XOR)
- 8:23Randomness
- 13:30One time pad (OTP)
- 15:08One time? But why?
- 15:55Stream cipher (more practical OTP)
- 21:02Block cipher primitive
- 21:27Electronic code block (ECB)
- 23:54Cipher block chaining (CBC)
- 24:51CBC decryption
- 31:55Padding (for block ciphers)
- 38:12What about integrity?
- 38:58Bit flipping (stream cipher)
- 43:44Bit flipping (block cipher, CBC mode)
- 44:29Authenticated encryption
- 46:59Hash vs KDF
- 50:48Takeaways
- 52:49Further learning
