# Can you extract the seed from randomly generated perlin noise?

**URL:** <https://discourse.processing.org/t/can-you-extract-the-seed-from-randomly-generated-perlin-noise/31023>\
**Category:** Coding Questions\
**Created:** [July 2, 2021, 6:47pm UTC](https://discourse.processing.org/t/can-you-extract-the-seed-from-randomly-generated-perlin-noise/31023 "2021-07-02T18:47:33Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![TonyG](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/tonyg/32/13780_2.png) [@TonyG](https://discourse.processing.org/u/TonyG)\
**Post date:** [July 2, 2021, 6:47pm UTC](https://discourse.processing.org/t/can-you-extract-the-seed-from-randomly-generated-perlin-noise/31023/1 "2021-07-02T18:47:33Z")

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Can you get the seed from a randomly generated perlin noise graph?

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**Author:** ![paulgoux](https://avatars.discourse-cdn.com/v4/letter/p/b9bd4f/32.png) [@paulgoux](https://discourse.processing.org/u/paulgoux)\
**Post date:** [July 2, 2021, 7:24pm UTC](https://discourse.processing.org/t/can-you-extract-the-seed-from-randomly-generated-perlin-noise/31023/2 "2021-07-02T19:24:35Z")

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please check the reference, noise can be initialised with a value that you choose.

[https://p5js.org/reference/#/p5/noise](https://p5js.org/reference/#/p5/noise)

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**Author:** ![TonyG](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/tonyg/32/13780_2.png) [@TonyG](https://discourse.processing.org/u/TonyG)\
**Post date:** [July 2, 2021, 7:54pm UTC](https://discourse.processing.org/t/can-you-extract-the-seed-from-randomly-generated-perlin-noise/31023/3 "2021-07-02T19:54:52Z")

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Thanks. That wasn’t my question.

Can you extract a seed from a perlin noise graph you did not initialize a seed for?

Thanks.

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**Author:** ![KumuPaul](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/kumupaul/32/13072_2.png) [@KumuPaul](https://discourse.processing.org/u/KumuPaul)\
**Post date:** [July 2, 2021, 8:57pm UTC](https://discourse.processing.org/t/can-you-extract-the-seed-from-randomly-generated-perlin-noise/31023/4 "2021-07-02T20:57:08Z")

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In theory, this might be possible. [Perlin noise](https://en.wikipedia.org/wiki/Perlin_noise) is based on a continuous/smooth interpolation of values between randomly generated vectors at discreet intervals, and in p5.js that field of vectors is generated using a [Linear congruential generator](https://en.wikipedia.org/wiki/Linear_congruential_generator). LCGs are not cryptographically secure (which is to say that it is not necessarily difficult to reverse engineer the seed, or key from a sequence of output values). Here is [a blog post](https://www.johndcook.com/blog/2017/08/16/reverse-engineering-the-seed-of-a-linear-congruential-generator/) about finding a LCG seed that produces a specific output. I read over the source code for the noise function and it looks like this should be feasible assuming you can explicitly set the noiseDetail and get the output from `noise(0, 0, 0)`:

```auto
// p5.js LCG constants
// m is basically chosen to be large (as it is the max period)
// and for its relationships to a and c
const m = 4294967296;
// a - 1 should be divisible by m's prime factors
const a = 1664525;
// c and m should be co-prime
const c = 1013904223;

// p5.js perlin constants
const PERLIN_YWRAP = 16;
const PERLIN_ZWRAP = 256;

function setup() {
  createCanvas(400, 400);
  noLoop();

  noiseSeed(2701);
  noiseDetail(1);
  print(`Actual noise(0, 0, 0): ${noise(0, 0, 0)}`);

  let lcgInt0 = (a * 2701 + c) % m;
  print(`Expected lcg0: ${lcgInt0}`);
  let lcgVal0 = lcgInt0 / m;

  let n1 = lcgVal0; // perlin[of & PERLIN_SIZE];
  /*
  // copy and pasted from noise.js
  // All of these terms go to 0 and so they have no impact on the output of noise(0,0,0)
  n1 += 0; // rxf * (perlin[(of + 1) & PERLIN_SIZE] - n1);
  let n2 = perlin[(of + PERLIN_YWRAP) & PERLIN_SIZE];
  n2 += 0; // rxf * (perlin[(of + PERLIN_YWRAP + 1) & PERLIN_SIZE] - n2);
  n1 += 0; // ryf * (n2 - n1);

  of += PERLIN_ZWRAP;
  n2 = perlin[of & PERLIN_SIZE];
  n2 += 0; // rxf * (perlin[(of + 1) & PERLIN_SIZE] - n2);
  n3 = perlin[(of + PERLIN_YWRAP) & PERLIN_SIZE];
  n3 += 0; // rxf * (perlin[(of + PERLIN_YWRAP + 1) & PERLIN_SIZE] - n3);
  n2 += 0; // ryf * (n3 - n2);

  n1 += 0; // scaled_cosine(zf) * (n2 - n1); */

  
  print(`noise(0, 0, 0) predicted: ${n1 * 0.5}`);
  print(`lcg0 predicted from noise output: ${noise(0, 0, 0) * 2 * m}`);
}

function draw() {}

```

Now, if you wanted to find the seed based on the output for some arbitrary set of non-integer points that would be much harder.

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<div class="post-metadata">

**Author:** ![TonyG](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/tonyg/32/13780_2.png) [@TonyG](https://discourse.processing.org/u/TonyG)\
**Post date:** [July 3, 2021, 11:21am UTC](https://discourse.processing.org/t/can-you-extract-the-seed-from-randomly-generated-perlin-noise/31023/5 "2021-07-03T11:21:59Z")

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Wow! 😀 Thank you for doing all of this.