Not So Random

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.NET System.Random() Constructor … … public Random() : this(Environment.TickCount) { } Not So Random
.NET System.Random() Constructor … public Random() : this(Environment.TickCount) { } … … /*==================================TickCount=================================== **Action: Gets the number of ticks since the system was started. **Returns: The number of ticks since the system was started. **Arguments: None **Exceptions: None ==============================================================================*/ public static extern int TickCount { … • https://referencesource.microsoft.com/#mscorlib/system/random.cs,52 • https://referencesource.microsoft.com/#mscorlib/system/environment.cs,265 Not So Random
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Not So Random Exploiting Unsafe Ran
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Talk Overview 1. Theory: • Why?
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Why do we need random numbers? •
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Random numbers in Web Applications
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Concept of Randomness • define: r
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PRNG PRNG r = random.Random() Not S
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PRNG 16768642083820545282 323536147
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PRNG PRNG 16768642083820545282 3235
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PRNG Seeds, States and Periods 1. S
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PRNG Seeds and States Seed (/dev/ur
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CSPRNG vs PRNG 1. Non-Deterministic
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Language Examples Language Method P
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Internals Glance public Random(int
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Exploitation Theory • Want to obt
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Exploitation Theory Target PRNG Out
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Exploitation Theory Target PRNG Out
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Exploitation Theory Target PRNG Obt
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Exploitation Theory Our PRNG Obtain
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Untwister Brute Force Algorithm 101
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Demos 1. Brute Force • PHP mt_ran
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Overview - Brute Force 1. Generate
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Brute Force - Source class ResetPas
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PHP mt_rand()- Exploitation • Rec
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PHP mt_rand()- Exploitation • Tar
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PHP mt_rand()- Exploitation Theory
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PHP mt_rand() - Untwister uint32_t
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PHP mt_rand()- Exploitation root@ka
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Page 91 and 92: PHP mt_rand()- Exploitation “To r
Page 93 and 94: Demos 1. Brute Force • PHP mt_ran
Page 95 and 96: Overview - Brute Force Bounded Call
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Page 103 and 104: PHP mt_rand(0,61)- Exploitation •
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Page 109 and 110: PHP mt_rand(0,61)- Decoder #!/usr/b
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Page 113 and 114: PHP Bounded mt_rand() Constructor
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Page 117 and 118: PHP mt_rand(0,61)- Exploitation roo
Page 119 and 120: 4. Seed new PRNG with obtained seed
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Page 125 and 126: PHP mt_rand(0,61)- Exploitation Not
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Page 129 and 130: Overview - Weak Seeds 1. Generate a
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Page 139 and 140: .NET System.Random()- Exploitation
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Page 145 and 146: System.Random() Constructor • .NE
Page 147 and 148: System.Random() Untwister Patch int
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Page 161 and 162: Exploitation Theory Observed PRNG O
Page 163 and 164: Practical Exploitation - Tips • L
Page 165 and 166: Mitigations Need a truly random num
Page 167 and 168: Developers, Developers, Developers
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Not So Random

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