Let's get random: Under the hood of PHP 7's CSPRNG - ZendCon & OpenEnterprise 2018

Talk given at ZendCon & OpenEnterprise 2018

Randomness is really important in many cryptographic contexts. Unfortunately, true randomness is a non-trivial achievement for computers. In fact, using weak sources of randomness can leave your application open to myriad vulnerabilities. Enter a good cryptographically secure pseudorandom number generator (CSPRNG).

We’ll discuss the importance of using good sources of randomness, the CSPRNG options we had in PHP 5, and how the new-goodness CSPRNG functions in PHP 7 work under the hood.

Transcript

1. Random
   Under the hood of PHP 7’s
   Let’s get
   CSPRNG
   Sammy Kaye Powers
   Las Vegas, NV - 2018
   

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2. joind.in/talk/0e3b7
   @SammyK #zcoe18
   Slides
   Get the
   joind.in/talk/0e3b7
   

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3. joind.in/talk/0e3b7
   @SammyK #zcoe18
   CSPRNG?
   What is the PHP 7
   

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4. joind.in/talk/0e3b7
   @SammyK #zcoe18
   random_int()
   random_bytes()
   

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5. joind.in/talk/0e3b7
   @SammyK #zcoe18
   ext/standard/random.c
   

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6. joind.in/talk/0e3b7
   @SammyK #zcoe18
   The end
   

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7. joind.in/talk/0e3b7
   @SammyK #zcoe18
   Random?
   What is
   

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8. Red
   Yellow
   White
   Red
   Yellow
   White
   Red
   Yellow
   White
   Period: 3
   

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9. Jingle all the way,
   Oh what fun it is to ride
   In a one-horse open sleigh
   Predictable seed
   Jingle bells, jingle bells
   

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10. 74, 105, 110, 103, 108, 101, 32,
    97, 108, 108, 32,
    116, 104, 101, 32,
    119, 97, 121, 44
    Random, right?
    

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11. ASCII
    

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12. 74, 105, 110, 103, 108, 101, 32,
    chr()
    J, i, n, g, l, e, ,
    

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13. 97, 108, 108, 32,
    What’s the next word?
    a, l, l, ,
    

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14. 116, 104, 101, 32,
    t, h, e, ,
    

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15. 74, 105, 110, 103, 108, 101, 32,
    97, 108, 108, 32,
    Random, right?
    116, 104, 101, 32,
    nope!
    

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16. Felt?
    Remember how we
    

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17. 74, 105, 110, 103, 108, 101, 32,
    97, 108, 108, 32,
    116, 104, 101, 32,
    119, 97, 121, 44
    What’s the meaning?
    ASCII codes!
    Ah, right. Carry on then.
    Deterministic
    

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18. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Why
    did we think
    

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19. joind.in/talk/0e3b7
    @SammyK #zcoe18
    •Think of a two-digit number
    •Between one and one hundred
    •Both digits odd
    •Both digits different
    

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20. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Are you thinking of…
    37
    

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21. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Humans
    are bad at being random
    

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22. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Environment
    Can we use our
    to make better random numbers?
    

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23. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Time?
    Maybe the
    

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24. joind.in/talk/0e3b7
    @SammyK #zcoe18
    12:00, 12:01, 12:02, 12:03, 12:04, 12:05, 12:06, 12:07, 12:08, 12:09, 12:10, 12:11, 12:12, 12:13, 12:14, 12:15, 12:16, 12:17, 12:18,
    12:19, 12:20, 12:21, 12:22, 12:23, 12:24, 12:25, 12:26, 12:27, 12:28, 12:29, 12:30, 12:31, 12:32, 12:33, 12:34, 12:35, 12:36, 12:37,
    12:38, 12:39, 12:40, 12:41, 12:42, 12:43, 12:44, 12:45, 12:46, 12:47, 12:48, 12:49, 12:50, 12:51, 12:52, 12:53, 12:54, 12:55, 12:56,
    12:57, 12:58, 12:59, 1:00, 1:01, 1:02, 1:03, 1:04, 1:05, 1:06, 1:07, 1:08, 1:09, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18,
    1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40,
    1:41, 1:42, 1:43, 1:44, 1:45, 1:46, 1:47, 1:48, 1:49, 1:50, 1:51, 1:52, 1:53, 1:54, 1:55, 1:56, 1:57, 1:58, 1:59, 2:00, 2:01, 2:02,
    2:03, 2:04, 2:05, 2:06, 2:07, 2:08, 2:09, 2:10, 2:11, 2:12, 2:13, 2:14, 2:15, 2:16, 2:17, 2:18, 2:19, 2:20, 2:21, 2:22, 2:23, 2:24,
    2:25, 2:26, 2:27, 2:28, 2:29, 2:30, 2:31, 2:32, 2:33, 2:34, 2:35, 2:36, 2:37, 2:38, 2:39, 2:40, 2:41, 2:42, 2:43, 2:44, 2:45, 2:46,
    2:47, 2:48, 2:49, 2:50, 2:51, 2:52, 2:53, 2:54, 2:55, 2:56, 2:57, 2:58, 2:59, 3:00, 3:01, 3:02, 3:03, 3:04, 3:05, 3:06, 3:07, 3:08,
    3:09, 3:10, 3:11, 3:12, 3:13, 3:14, 3:15, 3:16, 3:17, 3:18, 3:19, 3:20, 3:21, 3:22, 3:23, 3:24, 3:25, 3:26, 3:27, 3:28, 3:29, 3:30,
    3:31, 3:32, 3:33, 3:34, 3:35, 3:36, 3:37, 3:38, 3:39, 3:40, 3:41, 3:42, 3:43, 3:44, 3:45, 3:46, 3:47, 3:48, 3:49, 3:50, 3:51, 3:52,
    3:53, 3:54, 3:55, 3:56, 3:57, 3:58, 3:59, 4:00, 4:01, 4:02, 4:03, 4:04, 4:05, 4:06, 4:07, 4:08, 4:09, 4:10, 4:11, 4:12, 4:13, 4:14,
    4:15, 4:16, 4:17, 4:18, 4:19, 4:20, 4:21, 4:22, 4:23, 4:24, 4:25, 4:26, 4:27, 4:28, 4:29, 4:30, 4:31, 4:32, 4:33, 4:34, 4:35, 4:36,
    4:37, 4:38, 4:39, 4:40, 4:41, 4:42, 4:43, 4:44, 4:45, 4:46, 4:47, 4:48, 4:49, 4:50, 4:51, 4:52, 4:53, 4:54, 4:55, 4:56, 4:57, 4:58,
    4:59, 5:00, 5:01, 5:02, 5:03, 5:04, 5:05, 5:06, 5:07, 5:08, 5:09, 5:10, 5:11, 5:12, 5:13, 5:14, 5:15, 5:16, 5:17, 5:18, 5:19, 5:20,
    5:21, 5:22, 5:23, 5:24, 5:25, 5:26, 5:27, 5:28, 5:29, 5:30, 5:31, 5:32, 5:33, 5:34, 5:35, 5:36, 5:37, 5:38, 5:39, 5:40, 5:41, 5:42,
    5:43, 5:44, 5:45, 5:46, 5:47, 5:48, 5:49, 5:50, 5:51, 5:52, 5:53, 5:54, 5:55, 5:56, 5:57, 5:58, 5:59, 6:00, 6:01, 6:02, 6:03, 6:04,
    6:05, 6:06, 6:07, 6:08, 6:09, 6:10, 6:11, 6:12, 6:13, 6:14, 6:15, 6:16, 6:17, 6:18, 6:19, 6:20, 6:21, 6:22, 6:23, 6:24, 6:25, 6:26,
    6:27, 6:28, 6:29, 6:30, 6:31, 6:32, 6:33, 6:34, 6:35, 6:36, 6:37, 6:38, 6:39, 6:40, 6:41, 6:42, 6:43, 6:44, 6:45, 6:46, 6:47, 6:48,
    6:49, 6:50, 6:51, 6:52, 6:53, 6:54, 6:55, 6:56, 6:57, 6:58, 6:59, 7:00, 7:01, 7:02, 7:03, 7:04, 7:05, 7:06, 7:07, 7:08, 7:09, 7:10,
    7:11, 7:12, 7:13, 7:14, 7:15, 7:16, 7:17, 7:18, 7:19, 7:20, 7:21, 7:22, 7:23, 7:24, 7:25, 7:26, 7:27, 7:28, 7:29, 7:30, 7:31, 7:32,
    7:33, 7:34, 7:35, 7:36, 7:37, 7:38, 7:39, 7:40, 7:41, 7:42, 7:43, 7:44, 7:45, 7:46, 7:47, 7:48, 7:49, 7:50, 7:51, 7:52, 7:53, 7:54,
    7:55, 7:56, 7:57, 7:58, 7:59, 8:00, 8:01, 8:02, 8:03, 8:04, 8:05, 8:06, 8:07, 8:08, 8:09, 8:10, 8:11, 8:12, 8:13, 8:14, 8:15, 8:16,
    8:17, 8:18, 8:19, 8:20, 8:21, 8:22, 8:23, 8:24, 8:25, 8:26, 8:27, 8:28, 8:29, 8:30, 8:31, 8:32, 8:33, 8:34, 8:35, 8:36, 8:37, 8:38,
    8:39, 8:40, 8:41, 8:42, 8:43, 8:44, 8:45, 8:46, 8:47, 8:48, 8:49, 8:50, 8:51, 8:52, 8:53, 8:54, 8:55, 8:56, 8:57, 8:58, 8:59, 9:00,
    9:01, 9:02, 9:03, 9:04, 9:05, 9:06, 9:07, 9:08, 9:09, 9:10, 9:11, 9:12, 9:13, 9:14, 9:15, 9:16, 9:17, 9:18, 9:19, 9:20, 9:21, 9:22,
    9:23, 9:24, 9:25, 9:26, 9:27, 9:28, 9:29, 9:30, 9:31, 9:32, 9:33, 9:34, 9:35, 9:36, 9:37, 9:38, 9:39, 9:40, 9:41, 9:42, 9:43, 9:44,
    9:45, 9:46, 9:47, 9:48, 9:49, 9:50, 9:51, 9:52, 9:53, 9:54, 9:55, 9:56, 9:57, 9:58, 9:59, 10:00, 10:01, 10:02, 10:03, 10:04, 10:05,
    10:06, 10:07, 10:08, 10:09, 10:10, 10:11, 10:12, 10:13, 10:14, 10:15, 10:16, 10:17, 10:18, 10:19, 10:20, 10:21, 10:22, 10:23, 10:24,
    10:25, 10:26, 10:27, 10:28, 10:29, 10:30, 10:31, 10:32, 10:33, 10:34, 10:35, 10:36, 10:37, 10:38, 10:39, 10:40, 10:41, 10:42, 10:43,
    10:44, 10:45, 10:46, 10:47, 10:48, 10:49, 10:50, 10:51, 10:52, 10:53, 10:54, 10:55, 10:56, 10:57, 10:58, 10:59, 11:00, 11:01, 11:02,
    11:03, 11:04, 11:05, 11:06, 11:07, 11:08, 11:09, 11:10, 11:11, 11:12, 11:13, 11:14, 11:15, 11:16, 11:17, 11:18, 11:19, 11:20, 11:21,
    11:22, 11:23, 11:24, 11:25, 11:26, 11:27, 11:28, 11:29, 11:30, 11:31, 11:32, 11:33, 11:34, 11:35, 11:36, 11:37, 11:38, 11:39, 11:40,
    11:41, 11:42, 11:43, 11:44, 11:45, 11:46, 11:47, 11:48, 11:49, 11:50, 11:51, 11:52, 11:53, 11:54, 11:55, 11:56, 11:57, 11:58, 11:59
    720
    

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25. joind.in/talk/0e3b7
    @SammyK #zcoe18
    12:00, 12:01, 12:02, 12:03, 12:04, 12:05, 12:06, 12:07, 12:08, 12:09, 12:10, 12:11, 12:12, 12:13, 12:14, 12:15, 12:16, 12:17, 12:18,
    12:19, 12:20, 12:21, 12:22, 12:23, 12:24, 12:25, 12:26, 12:27, 12:28, 12:29, 12:30, 12:31, 12:32, 12:33, 12:34, 12:35, 12:36, 12:37,
    12:38, 12:39, 12:40, 12:41, 12:42, 12:43, 12:44, 12:45, 12:46, 12:47, 12:48, 12:49, 12:50, 12:51, 12:52, 12:53, 12:54, 12:55, 12:56,
    12:57, 12:58, 12:59, 1:00, 1:01, 1:02, 1:03, 1:04, 1:05, 1:06, 1:07, 1:08, 1:09, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18,
    1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40,
    1:41, 1:42, 1:43, 1:44, 1:45, 1:46, 1:47, 1:48, 1:49, 1:50, 1:51, 1:52, 1:53, 1:54, 1:55, 1:56, 1:57, 1:58, 1:59, 2:00, 2:01, 2:02,
    2:03, 2:04, 2:05, 2:06, 2:07, 2:08, 2:09, 2:10, 2:11, 2:12, 2:13, 2:14, 2:15, 2:16, 2:17, 2:18, 2:19, 2:20, 2:21, 2:22, 2:23, 2:24,
    2:25, 2:26, 2:27, 2:28, 2:29, 2:30, 2:31, 2:32, 2:33, 2:34, 2:35, 2:36, 2:37, 2:38, 2:39, 2:40, 2:41, 2:42, 2:43, 2:44, 2:45, 2:46,
    2:47, 2:48, 2:49, 2:50, 2:51, 2:52, 2:53, 2:54, 2:55, 2:56, 2:57, 2:58, 2:59, 3:00, 3:01, 3:02, 3:03, 3:04, 3:05, 3:06, 3:07, 3:08,
    3:09, 3:10, 3:11, 3:12, 3:13, 3:14, 3:15, 3:16, 3:17, 3:18, 3:19, 3:20, 3:21, 3:22, 3:23, 3:24, 3:25, 3:26, 3:27, 3:28, 3:29, 3:30,
    3:31, 3:32, 3:33, 3:34, 3:35, 3:36, 3:37, 3:38, 3:39, 3:40, 3:41, 3:42, 3:43, 3:44, 3:45, 3:46, 3:47, 3:48, 3:49, 3:50, 3:51, 3:52,
    3:53, 3:54, 3:55, 3:56, 3:57, 3:58, 3:59, 4:00, 4:01, 4:02, 4:03, 4:04, 4:05, 4:06, 4:07, 4:08, 4:09, 4:10, 4:11, 4:12, 4:13, 4:14,
    4:15, 4:16, 4:17, 4:18, 4:19, 4:20, 4:21, 4:22, 4:23, 4:24, 4:25, 4:26, 4:27, 4:28, 4:29, 4:30, 4:31, 4:32, 4:33, 4:34, 4:35, 4:36,
    4:37, 4:38, 4:39, 4:40, 4:41, 4:42, 4:43, 4:44, 4:45, 4:46, 4:47, 4:48, 4:49, 4:50, 4:51, 4:52, 4:53, 4:54, 4:55, 4:56, 4:57, 4:58,
    4:59, 5:00, 5:01, 5:02, 5:03, 5:04, 5:05, 5:06, 5:07, 5:08, 5:09, 5:10, 5:11, 5:12, 5:13, 5:14, 5:15, 5:16, 5:17, 5:18, 5:19, 5:20,
    5:21, 5:22, 5:23, 5:24, 5:25, 5:26, 5:27, 5:28, 5:29, 5:30, 5:31, 5:32, 5:33, 5:34, 5:35, 5:36, 5:37, 5:38, 5:39, 5:40, 5:41, 5:42,
    5:43, 5:44, 5:45, 5:46, 5:47, 5:48, 5:49, 5:50, 5:51, 5:52, 5:53, 5:54, 5:55, 5:56, 5:57, 5:58, 5:59, 6:00, 6:01, 6:02, 6:03, 6:04,
    6:05, 6:06, 6:07, 6:08, 6:09, 6:10, 6:11, 6:12, 6:13, 6:14, 6:15, 6:16, 6:17, 6:18, 6:19, 6:20, 6:21, 6:22, 6:23, 6:24, 6:25, 6:26,
    6:27, 6:28, 6:29, 6:30, 6:31, 6:32, 6:33, 6:34, 6:35, 6:36, 6:37, 6:38, 6:39, 6:40, 6:41, 6:42, 6:43, 6:44, 6:45, 6:46, 6:47, 6:48,
    6:49, 6:50, 6:51, 6:52, 6:53, 6:54, 6:55, 6:56, 6:57, 6:58, 6:59, 7:00, 7:01, 7:02, 7:03, 7:04, 7:05, 7:06, 7:07, 7:08, 7:09, 7:10,
    7:11, 7:12, 7:13, 7:14, 7:15, 7:16, 7:17, 7:18, 7:19, 7:20, 7:21, 7:22, 7:23, 7:24, 7:25, 7:26, 7:27, 7:28, 7:29, 7:30, 7:31, 7:32,
    7:33, 7:34, 7:35, 7:36, 7:37, 7:38, 7:39, 7:40, 7:41, 7:42, 7:43, 7:44, 7:45, 7:46, 7:47, 7:48, 7:49, 7:50, 7:51, 7:52, 7:53, 7:54,
    7:55, 7:56, 7:57, 7:58, 7:59, 8:00, 8:01, 8:02, 8:03, 8:04, 8:05, 8:06, 8:07, 8:08, 8:09, 8:10, 8:11, 8:12, 8:13, 8:14, 8:15, 8:16,
    8:17, 8:18, 8:19, 8:20, 8:21, 8:22, 8:23, 8:24, 8:25, 8:26, 8:27, 8:28, 8:29, 8:30, 8:31, 8:32, 8:33, 8:34, 8:35, 8:36, 8:37, 8:38,
    8:39, 8:40, 8:41, 8:42, 8:43, 8:44, 8:45, 8:46, 8:47, 8:48, 8:49, 8:50, 8:51, 8:52, 8:53, 8:54, 8:55, 8:56, 8:57, 8:58, 8:59, 9:00,
    9:01, 9:02, 9:03, 9:04, 9:05, 9:06, 9:07, 9:08, 9:09, 9:10, 9:11, 9:12, 9:13, 9:14, 9:15, 9:16, 9:17, 9:18, 9:19, 9:20, 9:21, 9:22,
    9:23, 9:24, 9:25, 9:26, 9:27, 9:28, 9:29, 9:30, 9:31, 9:32, 9:33, 9:34, 9:35, 9:36, 9:37, 9:38, 9:39, 9:40, 9:41, 9:42, 9:43, 9:44,
    9:45, 9:46, 9:47, 9:48, 9:49, 9:50, 9:51, 9:52, 9:53, 9:54, 9:55, 9:56, 9:57, 9:58, 9:59, 10:00, 10:01, 10:02, 10:03, 10:04, 10:05,
    10:06, 10:07, 10:08, 10:09, 10:10, 10:11, 10:12, 10:13, 10:14, 10:15, 10:16, 10:17, 10:18, 10:19, 10:20, 10:21, 10:22, 10:23, 10:24,
    10:25, 10:26, 10:27, 10:28, 10:29, 10:30, 10:31, 10:32, 10:33, 10:34, 10:35, 10:36, 10:37, 10:38, 10:39, 10:40, 10:41, 10:42, 10:43,
    10:44, 10:45, 10:46, 10:47, 10:48, 10:49, 10:50, 10:51, 10:52, 10:53, 10:54, 10:55, 10:56, 10:57, 10:58, 10:59, 11:00, 11:01, 11:02,
    11:03, 11:04, 11:05, 11:06, 11:07, 11:08, 11:09, 11:10, 11:11, 11:12, 11:13, 11:14, 11:15, 11:16, 11:17, 11:18, 11:19, 11:20, 11:21,
    11:22, 11:23, 11:24, 11:25, 11:26, 11:27, 11:28, 11:29, 11:30, 11:31, 11:32, 11:33, 11:34, 11:35, 11:36, 11:37, 11:38, 11:39, 11:40,
    11:41, 11:42, 11:43, 11:44, 11:45, 11:46, 11:47, 11:48, 11:49, 11:50, 11:51, 11:52, 11:53, 11:54, 11:55, 11:56, 11:57, 11:58, 11:59
    BUT!
    

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26. joind.in/talk/0e3b7
    @SammyK #zcoe18
    12:00, 12:01, 12:02, 12:03, 12:04, 12:05, 12:06, 12:07, 12:08, 12:09, 12:10, 12:11, 12:12, 12:13, 12:14, 12:15, 12:16, 12:17, 12:18,
    12:19, 12:20, 12:21, 12:22, 12:23, 12:24, 12:25, 12:26, 12:27, 12:28, 12:29, 12:30, 12:31, 12:32, 12:33, 12:34, 12:35, 12:36, 12:37,
    12:38, 12:39, 12:40, 12:41, 12:42, 12:43, 12:44, 12:45, 12:46, 12:47, 12:48, 12:49, 12:50, 12:51, 12:52, 12:53, 12:54, 12:55, 12:56,
    12:57, 12:58, 12:59, 1:00, 1:01, 1:02, 1:03, 1:04, 1:05, 1:06, 1:07, 1:08, 1:09, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18,
    1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39, 1:40,
    1:41, 1:42, 1:43, 1:44, 1:45, 1:46, 1:47, 1:48, 1:49, 1:50, 1:51, 1:52, 1:53, 1:54, 1:55, 1:56, 1:57, 1:58, 1:59, 2:00, 2:01, 2:02,
    2:03, 2:04, 2:05, 2:06, 2:07, 2:08, 2:09, 2:10, 2:11, 2:12, 2:13, 2:14, 2:15, 2:16, 2:17, 2:18, 2:19, 2:20, 2:21, 2:22, 2:23, 2:24,
    2:25, 2:26, 2:27, 2:28, 2:29, 2:30, 2:31, 2:32, 2:33, 2:34, 2:35, 2:36, 2:37, 2:38, 2:39, 2:40, 2:41, 2:42, 2:43, 2:44, 2:45, 2:46,
    2:47, 2:48, 2:49, 2:50, 2:51, 2:52, 2:53, 2:54, 2:55, 2:56, 2:57, 2:58, 2:59, 3:00, 3:01, 3:02, 3:03, 3:04, 3:05, 3:06, 3:07, 3:08,
    3:09, 3:10, 3:11, 3:12, 3:13, 3:14, 3:15, 3:16, 3:17, 3:18, 3:19, 3:20, 3:21, 3:22, 3:23, 3:24, 3:25, 3:26, 3:27, 3:28, 3:29, 3:30,
    3:31, 3:32, 3:33, 3:34, 3:35, 3:36, 3:37, 3:38, 3:39, 3:40, 3:41, 3:42, 3:43, 3:44, 3:45, 3:46, 3:47, 3:48, 3:49, 3:50, 3:51, 3:52,
    3:53, 3:54, 3:55, 3:56, 3:57, 3:58, 3:59, 4:00, 4:01, 4:02, 4:03, 4:04, 4:05, 4:06, 4:07, 4:08, 4:09, 4:10, 4:11, 4:12, 4:13, 4:14,
    4:15, 4:16, 4:17, 4:18, 4:19, 4:20, 4:21, 4:22, 4:23, 4:24, 4:25, 4:26, 4:27, 4:28, 4:29, 4:30, 4:31, 4:32, 4:33, 4:34, 4:35, 4:36,
    4:37, 4:38, 4:39, 4:40, 4:41, 4:42, 4:43, 4:44, 4:45, 4:46, 4:47, 4:48, 4:49, 4:50, 4:51, 4:52, 4:53, 4:54, 4:55, 4:56, 4:57, 4:58,
    4:59, 5:00, 5:01, 5:02, 5:03, 5:04, 5:05, 5:06, 5:07, 5:08, 5:09, 5:10, 5:11, 5:12, 5:13, 5:14, 5:15, 5:16, 5:17, 5:18, 5:19, 5:20,
    5:21, 5:22, 5:23, 5:24, 5:25, 5:26, 5:27, 5:28, 5:29, 5:30, 5:31, 5:32, 5:33, 5:34, 5:35, 5:36, 5:37, 5:38, 5:39, 5:40, 5:41, 5:42,
    5:43, 5:44, 5:45, 5:46, 5:47, 5:48, 5:49, 5:50, 5:51, 5:52, 5:53, 5:54, 5:55, 5:56, 5:57, 5:58, 5:59, 6:00, 6:01, 6:02, 6:03, 6:04,
    6:05, 6:06, 6:07, 6:08, 6:09, 6:10, 6:11, 6:12, 6:13, 6:14, 6:15, 6:16, 6:17, 6:18, 6:19, 6:20, 6:21, 6:22, 6:23, 6:24, 6:25, 6:26,
    6:27, 6:28, 6:29, 6:30, 6:31, 6:32, 6:33, 6:34, 6:35, 6:36, 6:37, 6:38, 6:39, 6:40, 6:41, 6:42, 6:43, 6:44, 6:45, 6:46, 6:47, 6:48,
    6:49, 6:50, 6:51, 6:52, 6:53, 6:54, 6:55, 6:56, 6:57, 6:58, 6:59, 7:00, 7:01, 7:02, 7:03, 7:04, 7:05, 7:06, 7:07, 7:08, 7:09, 7:10,
    7:11, 7:12, 7:13, 7:14, 7:15, 7:16, 7:17, 7:18, 7:19, 7:20, 7:21, 7:22, 7:23, 7:24, 7:25, 7:26, 7:27, 7:28, 7:29, 7:30, 7:31, 7:32,
    7:33, 7:34, 7:35, 7:36, 7:37, 7:38, 7:39, 7:40, 7:41, 7:42, 7:43, 7:44, 7:45, 7:46, 7:47, 7:48, 7:49, 7:50, 7:51, 7:52, 7:53, 7:54,
    7:55, 7:56, 7:57, 7:58, 7:59, 8:00, 8:01, 8:02, 8:03, 8:04, 8:05, 8:06, 8:07, 8:08, 8:09, 8:10, 8:11, 8:12, 8:13, 8:14, 8:15, 8:16,
    8:17, 8:18, 8:19, 8:20, 8:21, 8:22, 8:23, 8:24, 8:25, 8:26, 8:27, 8:28, 8:29, 8:30, 8:31, 8:32, 8:33, 8:34, 8:35, 8:36, 8:37, 8:38,
    8:39, 8:40, 8:41, 8:42, 8:43, 8:44, 8:45, 8:46, 8:47, 8:48, 8:49, 8:50, 8:51, 8:52, 8:53, 8:54, 8:55, 8:56, 8:57, 8:58, 8:59, 9:00,
    9:01, 9:02, 9:03, 9:04, 9:05, 9:06, 9:07, 9:08, 9:09, 9:10, 9:11, 9:12, 9:13, 9:14, 9:15, 9:16, 9:17, 9:18, 9:19, 9:20, 9:21, 9:22,
    9:23, 9:24, 9:25, 9:26, 9:27, 9:28, 9:29, 9:30, 9:31, 9:32, 9:33, 9:34, 9:35, 9:36, 9:37, 9:38, 9:39, 9:40, 9:41, 9:42, 9:43, 9:44,
    9:45, 9:46, 9:47, 9:48, 9:49, 9:50, 9:51, 9:52, 9:53, 9:54, 9:55, 9:56, 9:57, 9:58, 9:59, 10:00, 10:01, 10:02, 10:03, 10:04, 10:05,
    10:06, 10:07, 10:08, 10:09, 10:10, 10:11, 10:12, 10:13, 10:14, 10:15, 10:16, 10:17, 10:18, 10:19, 10:20, 10:21, 10:22, 10:23, 10:24,
    10:25, 10:26, 10:27, 10:28, 10:29, 10:30, 10:31, 10:32, 10:33, 10:34, 10:35, 10:36, 10:37, 10:38, 10:39, 10:40, 10:41, 10:42, 10:43,
    10:44, 10:45, 10:46, 10:47, 10:48, 10:49, 10:50, 10:51, 10:52, 10:53, 10:54, 10:55, 10:56, 10:57, 10:58, 10:59, 11:00, 11:01, 11:02,
    11:03, 11:04, 11:05, 11:06, 11:07, 11:08, 11:09, 11:10, 11:11, 11:12, 11:13, 11:14, 11:15, 11:16, 11:17, 11:18, 11:19, 11:20, 11:21,
    11:22, 11:23, 11:24, 11:25, 11:26, 11:27, 11:28, 11:29, 11:30, 11:31, 11:32, 11:33, 11:34, 11:35, 11:36, 11:37, 11:38, 11:39, 11:40,
    11:41, 11:42, 11:43, 11:44, 11:45, 11:46, 11:47, 11:48, 11:49, 11:50, 11:51, 11:52, 11:53, 11:54, 11:55, 11:56, 11:57, 11:58, 11:59
    • Session started at 4:00 pm PDT
    • That was on slide #23
    • If you timed my rehearsals…
    

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27. joind.in/talk/0e3b7
    @SammyK #zcoe18
    11
    random?
    What makes a number
    

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28. joind.in/talk/0e3b7
    @SammyK #zcoe18
    2, 4, 6, 8, __
    10
    

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29. joind.in/talk/0e3b7
    @SammyK #zcoe18
    1337, 42, 0, _
    ?
    

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30. joind.in/talk/0e3b7
    @SammyK #zcoe18
    1337, 42, 0,
    1337, 42, 0,
    1337, __
    42
    

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31. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Random?
    What is isn’t
    Deterministic
    

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32. joind.in/talk/0e3b7
    @SammyK #zcoe18
    “True” Random
    Measurement of atmospheric noise
    Count of the number of electrons
    coming off of a radioactive material
    

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33. View Slide

34. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Can I haz
    random number?
    

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35. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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36. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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37. joind.in/talk/0e3b7
    @SammyK #zcoe18
    *sigh* Take this.
    42
    

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38. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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39. joind.in/talk/0e3b7
    @SammyK #zcoe18
    0
    

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40. joind.in/talk/0e3b7
    @SammyK #zcoe18
    2,4,8,
    7,5,1
    ?
    

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41. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Number Generator
    …or “PRNG” for short
    Pseudorandom
    

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42. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Pseudorandom?
    How’s that different than just random?
    Deterministic
    

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43. joind.in/talk/0e3b7
    @SammyK #zcoe18
    2,4,8,
    7,5,1
    Generator
    Linear Congruential
    

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44. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Generator
    Linear Congruential
    

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45. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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46. joind.in/talk/0e3b7
    @SammyK #zcoe18
    The modulus
    The multiplier
    The increment
    The seed
    

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47. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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48. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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49. joind.in/talk/0e3b7
    @SammyK #zcoe18
    2,4,8,
    7,5,
    

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50. joind.in/talk/0e3b7
    @SammyK #zcoe18
    2,4,8,
    7,5,
    Deterministic
    

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51. joind.in/talk/0e3b7
    @SammyK #zcoe18
    https://xkcd.com/221/
    

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52. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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53. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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54. joind.in/talk/0e3b7
    @SammyK #zcoe18
    8,7,5,
    1,2,
    

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55. joind.in/talk/0e3b7
    @SammyK #zcoe18
    1,2,4,
    8,7,
    BUT!
    

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56. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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57. 5,1,2,4,8,7,5,
    1,2,4,8,7,5,1,
    2,4,8,7,5,1,2,
    4,8,7,5,1,2,4,
    8,7,5,1,2,4,8,
    7,5,1,2,4,
    Predictable
    Period: 6
    

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58. joind.in/talk/0e3b7
    @SammyK #zcoe18
    LCG
    lcg_value()
    PHP has a combined
    

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59. joind.in/talk/0e3b7
    @SammyK #zcoe18
    PRNG?
    Is there a better
    

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60. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Twister
    Mersenne
    mt_rand()
    

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61. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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62. mt_rand()
    724937621,955931554,1407935661,821438740,109344
    9922,603009103,1540988686,1028238631,798475733,
    1057939018,671583233,1853117923,98760648,112245
    3373,534404057,900958085,1712824654,476385742,2
    9956470,362833620,424798798,746223917,942003531
    ,320462445,673296853,1351199651,141566289,16454
    09515,995047403,1216151582,1115999460,175322091
    7,1312071810,1553254094,1622498991,2080099801,1
    704834715,1537620663,1357630828,1317892558,
    219,937-1
    

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63. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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64. mt_rand(0,99)
    83,9,64,28,62,48,83,47,46,53,37,26,21,91,61,32,58,1,89,60,65,97,42,56,6,47,76,1
    2,98,11,36,61,62,60,43,67,6,16,73,15,39,38,56,19,66,56,98,72,91,24,57,94,8,26,7
    3,55,17,14,84,89,39,11,13,48,71,98,89,63,9,95,74,9,81,85,97,24,14,14,77,22,96,4
    3,61,91,61,58,19,71,8,49,18,92,38,34,9,36,91,59,14,4,58,59,29,74,52,41,36,67,82
    ,67,11,0,58,51,37,4,45,56,35,50,78,91,27,39,80,27,28,95,2,82,51,72,27,41,43,74,
    7,82,59,89,72,9,22,61,75,27,64,16,77,57,31,29,59,47,14,67,89,33,94,33,94,22,11,
    62,9,13,61,45,78,29,3,11,99,91,52,79,63,64,43,99,53,22,16,10,53,57,15,84,16,30,
    17,10,3,35,0,45,83,11,70,66,37,14,59,41,46,52,53,53,62,56,41,82,40,99,8,92,96,2
    2,22,43,35,60,45,77,26,96,45,51,62,77,64,23,52,17,17,97,93,57,43,56,45,62,42,24
    ,62,1,59,38,70,13,34,32,48,47,1,42,48,18,2,59,47,53,10,3,66,68,93,4,53,85,20,77
    ,63,43,45,16,15,77,73,89,11,64,76,30,46,91,1,85,96,19,63,70,62,35,58,95,63,38,7
    8,83,8,97,22,2,28,51,25,29,98,62,74,59,95,79,74,66,47,35,83,56,49,25,32,25,46,1
    3,69,77,30,94,24,31,68,23,64,47,28,33,65,69,16,0,98,37,85,93,60,24,10,54,50,42,
    64,11,9,13,15,84,3,23,73,83,83,72,9,2,28,23,90,73,2,47,45,93,4,32,25,75,61,98,7
    3,79,66,23,20,83,11,45,67,40,39,45,0,65,40,78,74,8,79,86,38,10,87,60,99,30,35,5
    0,16,29,24,19,29,16,40,57,87,26,90,1,63,63,34,44,8,36,25,38,50,10,15,17,14,40,6
    ,53,88,18,36,46,69,2,13,0,83,59,92,59,34,34,24,40,99,41,6,79,65,98,9,36,31,8,4,
    89,98,91,80,42,10,26,72,40,50,39,25,33,45,24,70,54,89,91,53,23,12,20,40,21,25,5
    5,48,11,3,84,42,5,7,21,58,85,18,52,92,94,69,20,49,3,8,55,57,4,38,52,37,64,55,82
    ,98,5,75,84,35,14,99,74,23,41,69,55,53,22,52,6,68,35,38,73,52,22,52,86,79,15,38
    ,3,20,99,36,23,77,33,80,16,97,54,88,11,77,77,99,70,26,5,75,87,4,23,8,50,79,61,5
    5,80,25,58,79,25,56,9,81,6,42,27,90,58,6,62,74,25,79,81,61,23,54,92,53,16,66,22
    ,49,77,97,84,25,49,32,49,65,51,1,93,63,68,69,67,10,44,99,44,42,89,35,24,
    624 = busted
    

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65. echo mt_rand(0,99);
    11
    

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66. echo mt_rand(0,99);
    9
    

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67. echo mt_rand(0,99);
    60
    

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68. mt_srand(10);
    echo mt_rand(0,99);
    21
    

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69. mt_srand(10);
    echo mt_rand(0,99);
    21
    

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70. mt_srand(10);
    echo mt_rand(0,99);
    21
    

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71. View Slide

72. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Good
    randomness can be
    Deterministic
    (e.g. games)
    

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73. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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74. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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75. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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76. joind.in/talk/0e3b7
    @SammyK #zcoe18
    AKA “Seed”
    

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77. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

    View Slide

78. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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79. joind.in/talk/0e3b7
    @SammyK #zcoe18
    deterministic randomness is
    contexts
    In cryptographic
    really, really, really, really
    objectively…
    

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80. joind.in/talk/0e3b7
    @SammyK #zcoe18
    BAD
    

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81. joind.in/talk/0e3b7
    @SammyK #zcoe18
    CSRF
    Take for example
    Tokens
    

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82. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Cross-site request forgery
    (CSRF) tokens help prevent
    unauthorized requests on
    a user’s behalf.
    

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83. joind.in/talk/0e3b7
    @SammyK #zcoe18
    A CSRF token must be
    unique and unpredictable.
    *don’t do this
    

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84. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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85. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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86. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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87. joind.in/talk/0e3b7
    @SammyK #zcoe18
    I’ll just let PHP seed
    mt_rand() for me.
    Bad idea jeans
    *Old SNL skit reference
    

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88. joind.in/talk/0e3b7
    @SammyK #zcoe18
    

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89. joind.in/talk/0e3b7
    @SammyK #zcoe18
    What about
    rand()
    you ask?
    

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90. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Nope
    

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91. joind.in/talk/0e3b7
    @SammyK #zcoe18
    rand()
    mt_rand()
    …in PHP 7.0 & below
    

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92. joind.in/talk/0e3b7
    @SammyK #zcoe18
    rand()
    Uses the system PRNG
    (unreliable & inconsistent)
    Is a PRNG (totes predictable)
    Uniform distribution issues
    

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93. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Uniform
    Distribution
    

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94. joind.in/talk/0e3b7
    @SammyK #zcoe18
    0
    0.05
    0.1
    0.15
    0.2
    1 2 3 4 5 6
    

    View Slide

95. joind.in/talk/0e3b7
    @SammyK #zcoe18
    0
    0.1
    0.2
    0.3
    0.4
    1 2 3 4 5 6
    

    View Slide

96. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Uniform Distribution
    ==
    True Random
    

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97. joind.in/talk/0e3b7
    @SammyK #zcoe18
    mt_rand()
    Implements the MT algorithm
    incorrectly
    Is a PRNG (totes predictable)
    Has a modulo bias
    

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98. joind.in/talk/0e3b7
    @SammyK #zcoe18
    Modulo
    Bias
    

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99. joind.in/talk/0e3b7
    @SammyK #zcoe18
    6 % 3 = 0
    8 % 3 = 2
    Modulo Operator
    

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100. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Random # between 0 & 1
     n % 2 = 0 or 1
     Use mod 2
     

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101. joind.in/talk/0e3b7
     @SammyK #zcoe18
     rand_src() = 1, 2, or 3
     2 % 2 = 0
     3 % 2 = 1
     1 is
     more likely
     1 % 2 = 1
     

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102. joind.in/talk/0e3b7
     @SammyK #zcoe18
     rand()
     mt_rand()
     …in PHP 7.1 & above
     

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103. joind.in/talk/0e3b7
     @SammyK #zcoe18
     mt_rand()
     Fixes bug in MT algorithm
     implementation
     Is a PRNG (totes predictable)
     

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104. joind.in/talk/0e3b7
     @SammyK #zcoe18
     They’re totes
     samezies!
     rand() mt_rand()
     ===
     

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105. joind.in/talk/0e3b7
     @SammyK #zcoe18
     

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106. joind.in/talk/0e3b7
     @SammyK #zcoe18
     rand() mt_rand()
     Both suffer from
     modulo bias
     &
     

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107. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Seeds aren’t
     impossible to predict
     

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108. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Entropy
     *Could be it’s own talk
     

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109. joind.in/talk/0e3b7
     @SammyK #zcoe18
     A measure of how
     accurately we’re able
     to predict the next
     value in a sequence.*
     * oversimplification
     

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110. joind.in/talk/0e3b7
     @SammyK #zcoe18
     High
     entropy
     harder
     to predict
     Low
     entropy
     easier
     to predict
     

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111. joind.in/talk/0e3b7
     @SammyK #zcoe18
     High
     entropy
     harder
     to predict Good for random
     number generation
     

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112. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Cryptographically
     Pseudorandom
     Secure
     Number Generator
     

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113. joind.in/talk/0e3b7
     @SammyK #zcoe18
     CSPRNG
     or…
     

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114. joind.in/talk/0e3b7
     @SammyK #zcoe18
     “See Spring”
     or…
     

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115. Unicorn
     Magical
     

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116. Uses seeds
     that are really
     really
     really
     really
     ridiculously
     hard to guess
     

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117. joind.in/talk/0e3b7
     @SammyK #zcoe18
     High
     Entropy
     wee!
     

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118. joind.in/talk/0e3b7
     @SammyK #zcoe18
     impossible
     It’s values are
     to predict in practice
     42
     82
     
     Suitable for use in
     cryptographic contexts.
     

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119. mythical
     Where can we find this
     creature?
     

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120. joind.in/talk/0e3b7
     @SammyK #zcoe18
     CSPRNG
     options in
     5.x
     

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121. joind.in/talk/0e3b7
     @SammyK #zcoe18
     openssl_random_pseudo_bytes()
     mcrypt_create_iv()
     /dev/urandom
     

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122. joind.in/talk/0e3b7
     @SammyK #zcoe18
     openssl_random_pseudo_bytes()
     mcrypt_create_iv()
     /dev/urandom
     

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123. joind.in/talk/0e3b7
     @SammyK #zcoe18
     

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124. joind.in/talk/0e3b7
     @SammyK #zcoe18
     TAKE_
     to_live
     TAKE_
     to_lie
     

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125. joind.in/talk/0e3b7
     @SammyK #zcoe18
     TAKE_
     to_lie
     5.6.11
     

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126. joind.in/talk/0e3b7
     @SammyK #zcoe18
     5.6.12
     TAKE_
     to_live
     

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127. Fails
     open
     

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128. joind.in/talk/0e3b7
     @SammyK #zcoe18
     FALSE
     Can return
     

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129. joind.in/talk/0e3b7
     @SammyK #zcoe18
     empty string
     Can be
     

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130. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Still not done!
     

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131. joind.in/talk/0e3b7
     @SammyK #zcoe18
     WRONG
     Easy to get
     

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132. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Worse
     It gets
     

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133. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Since the UNIX fork() system call
     duplicates the entire process state, a
     random number generator which does not
     take this issue into account will produce
     the same sequence of random numbers in
     both the parent and the child […], leading to
     cryptographic disaster…
     https://wiki.openssl.org/index.php/Random_fork-safety
     

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134. joind.in/talk/0e3b7
     @SammyK #zcoe18
     OpenSSL’s
     be like
     42
     CSPRNG
     82
     
     82
     
     

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135. joind.in/talk/0e3b7
     @SammyK #zcoe18
     OpenSSL cannot fix the fork-safety
     problem because its not in a position
     to do so. However, there are [solutions]
     available and they are listed below.
     https://wiki.openssl.org/index.php/Random_fork-safety
     

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136. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Don't use
     RAND_bytes
     https://wiki.openssl.org/index.php/Random_fork-safety
     

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137. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Instead, you can read directly from
     /dev/random, /dev/urandom or
     /dev/srandom; or use CryptGenRandom
     on Windows systems.
     https://wiki.openssl.org/index.php/Random_fork-safety
     

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138. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Status update!
     v1.1.1
     (2018-09-11)
     

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139. joind.in/talk/0e3b7
     @SammyK #zcoe18
     mcrypt_create_iv()
     /dev/urandom
     openssl_random_pseudo_bytes()
     

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140. Fails
     open
     

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141. joind.in/talk/0e3b7
     @SammyK #zcoe18
     

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142. joind.in/talk/0e3b7
     @SammyK #zcoe18
     

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143. joind.in/talk/0e3b7
     @SammyK #zcoe18
     

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144. joind.in/talk/0e3b7
     @SammyK #zcoe18
     /dev/urandom
     openssl_random_pseudo_bytes()
     mcrypt_create_iv()
     

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145. joind.in/talk/0e3b7
     @SammyK #zcoe18
     open_basedir=/foo/dir
     

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146. joind.in/talk/0e3b7
     @SammyK #zcoe18
     openssl_random_pseudo_bytes()
     mcrypt_create_iv()
     /dev/urandom
     

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147. joind.in/talk/0e3b7
     @SammyK #zcoe18
     CSPRNG
     New goodness
     7
     

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148. joind.in/talk/0e3b7
     @SammyK #zcoe18
     CSPRNG
     random_int()
     random_bytes()
     

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149. random_int(0,99)
     6,17,6,9,17,53,58,98,46,44,62,9,76,65,46,21,42,5,65,34,11,96,85,7,46,89,98,9,9,
     80,8,76,87,18,24,68,16,61,27,39,30,32,4,83,83,23,96,27,13,47,6,99,16,40,2,75,27
     ,3,79,68,75,60,50,70,63,17,75,29,79,57,9,48,18,86,95,25,40,52,20,86,6,48,94,27,
     76,14,9,27,62,14,68,58,12,18,63,19,84,47,7,13,63,28,66,55,2,75,44,92,11,85,51,1
     7,42,57,22,4,53,7,3,76,48,55,95,7,45,33,87,36,11,17,66,6,46,87,57,48,22,31,65,5
     ,26,10,47,82,97,74,25,32,63,60,29,53,13,24,56,54,52,86,67,4,94,35,48,73,35,45,2
     4,74,74,83,49,70,41,49,20,60,29,49,30,35,38,63,4,86,72,97,26,22,36,95,59,94,24,
     89,73,46,14,73,51,93,93,39,13,80,9,30,24,20,30,63,20,64,97,29,7,2,82,96,42,61,5
     3,28,49,12,90,71,58,72,63,49,32,69,76,50,62,88,31,26,72,79,19,15,3,39,27,80,16,
     65,62,53,82,59,23,85,95,41,68,86,3,92,76,91,88,12,20,96,14,35,50,94,24,23,44,55
     ,78,65,81,7,1,86,32,58,46,97,43,78,9,51,1,6,79,73,49,13,40,21,90,14,9,70,95,88,
     37,85,14,7,29,42,55,81,46,39,41,45,81,11,93,26,89,4,98,35,30,36,74,97,18,85,97,
     23,52,64,88,20,89,12,25,19,21,21,50,60,50,43,84,1,52,5,19,2,86,38,51,48,30,55,9
     0,93,97,52,84,29,58,96,78,37,24,14,72,81,9,82,26,83,83,17,35,15,9,87,95,51,71,4
     8,9,45,13,61,98,3,18,96,99,28,74,47,58,71,89,68,57,51,86,90,38,21,72,72,30,22,1
     3,88,25,48,45,62,59,81,32,10,54,82,60,90,17,98,41,73,98,60,22,99,66,32,41,82,62
     ,91,3,85,91,21,17,98,19,48,50,24,67,3,14,62,55,35,99,95,83,76,12,51,77,61,24,24
     ,60,15,31,47,24,27,97,98,70,6,24,25,20,23,67,72,55,47,19,53,50,38,22,76,37,63,8
     2,67,52,3,75,84,84,71,49,79,26,89,11,77,55,92,32,81,38,23,54,9,40,80,75,20,7,58
     ,37,72,75,59,46,32,41,82,90,72,59,5,42,2,94,44,44,4,15,37,29,24,10,51,18,8,42,5
     6,9,68,31,99,7,77,59,8,74,80,11,15,93,81,5,72,44,49,39,25,4,18,98,0,93,42,78,36
     ,57,47,16,49,2,85,6,31,17,81,10,54,40,95,68,31,80,29,41,86,32,9,58,96,62,79,25,
     6,45,56,54,0,61,74,90,12,34,11,56,3,41,39,84,32,30,42,81,36,43,5,
     

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150. joind.in/talk/0e3b7
     @SammyK #zcoe18
     bin2hex(random_bytes(16))
     f7f5289027cb6c5116d
     2d3cc78e5819c
     

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151. Fails
     Closed
     

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152. joind.in/talk/0e3b7
     @SammyK #zcoe18
     You’re not strong until
     you’re crypto-strong!
     

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153. CSPRNG
     under the hood
     

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154. View Slide

155. joind.in/talk/0e3b7
     @SammyK #zcoe18
     On Windows: CryptGenRandom
     On BSD: arc4random_buf()
     On Linux: getrandom(2) syscall
     Read directly from /dev/urandom
     

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156. joind.in/talk/0e3b7
     @SammyK #zcoe18
     /dev/urandom
     So what is this
     thing?
     

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157. /dev/urandom
     Gathers environmental noise
     from the system like…
     …device drivers, inter-keyboard
     timings, inter-interrupt timings
     from some interrupts, and
     other events which are both
     (a) non-deterministic and
     (b) hard for an outside
     observer to measure.
     https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/random.c
     

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158. joind.in/talk/0e3b7
     @SammyK #zcoe18
     CSPRNG
     random_bytes()
     random_int()
     7
     /dev/urandom
     Powered by
     

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159. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Still on 5.x?
     paragonie/random_compat
     Polyfill for PHP 7 CSPRNG
     

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160. joind.in/talk/0e3b7
     @SammyK #zcoe18
     http://php.net/supported-versions.php
     5.6 EOL in 75 days
     

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161. joind.in/talk/0e3b7
     @SammyK #zcoe18
     http://php.net/supported-versions.php
     7.0 EOL in 47 days
     

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162. joind.in/talk/0e3b7
     @SammyK #zcoe18
     FAQ’s
     

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163. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Benchmarks*
     * are lies
     

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164. joind.in/talk/0e3b7
     @SammyK #zcoe18
     If random_bytes()
     random_int() are…
     …why not
     update
     mt_rand()
     

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165. joind.in/talk/0e3b7
     @SammyK #zcoe18
     

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166. joind.in/talk/0e3b7
     @SammyK #zcoe18
     

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167. joind.in/talk/0e3b7
     @SammyK #zcoe18
     TL;DR
     Never use LCG, MT, or any other PRNG in
     cryptographic contexts
     Only use a CSPRNG like
     /dev/urandom for crypto
     Use random_bytes() & random_int() in
     PHP (or install paragonie/random_compat)
     

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168. joind.in/talk/0e3b7
     @SammyK #zcoe18
     More Resources
     

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169. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Recommendation for the
     Entropy Sources Used for
     Random Bit Generation
     Final Draft - NIST SP 800-90B
     https://csrc.nist.gov/publications/detail/sp/800-90b/final
     

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170. joind.in/talk/0e3b7
     @SammyK #zcoe18
     New & improved man pages for
     /dev/urandom
     http://man7.org/linux/man-pages/man7/random.7.html
     

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171. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Myths about
     /dev/urandom
     Thomas Hühn
     https://www.2uo.de/myths-about-urandom/
     With pretty pictures!
     

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172. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Cracking Random Number Generators
     Three-part blog post series
     James Roper
     https://jazzy.id.au/2010/09/20/cracking_random_number_generators_part_1.html
     

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173. joind.in/talk/0e3b7
     @SammyK #zcoe18
     How I Met Your Girlfriend
     DEF CON 18
     Samy Kamkar
     https://www.youtube.com/watch?v=fWk_rMQiDGc
     

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174. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Weak RNG in PHP session ID generation
     leads to session hijacking
     Andreas Bogk
     http://seclists.org/fulldisclosure/2010/Mar/519
     

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175. joind.in/talk/0e3b7
     @SammyK #zcoe18
     Sammy Kaye Powers
     Thanks!
     /talk/0e3b7
     @SammyK
     SammyK.me
     Host of @PHPRoundtable
     

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