diff --git a/docs/functions/core/crypto/why2_random.md b/docs/functions/core/crypto/why2_random.md
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@@ -0,0 +1,40 @@
+<!--
+This is part of WHY2
+Copyright (C) 2022 Václav Šmejkal
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+-->
+
+# why2_random
+
+## Parameters
+
+| Identifier | Data type |
+| ---------- | --------- |
+| `dest`     | `void *`  |
+| `size`     | `size_t`  |
+
+## Attributes
+
+|                     |                                                          |
+| ------------------  | -------------------------------------------------------- |
+| **Return type**     | [`why2_bool`](../../../../types/core/flags/why2_bool.md) |
+| **Header comment**  | `WRITE CRYPTO-SECURE RANDOM NUMBER INTO dest`            |
+| **Added in commit** | [`f95608f52a0a82b3a8c005c7f8dad0b9cf93202a`](https://github.com/ENGO150/WHY2/commit/f95608f52a0a82b3a8c005c7f8dad0b9cf93202a) |
+
+## Description
+
+Function passes `dest` and `size` into [`RAND_bytes`](https://docs.openssl.org/1.1.1/man3/RAND_bytes) function and gets the output value. If output value is equal to `1`, returns `true`, otherwise `false`.
+
+`dest` is where the output value should be stored, `size` sets the allowed size to write. Should be `sizeof(dest_datatype)`.
\ No newline at end of file
diff --git a/docs/functions/index.md b/docs/functions/index.md
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--- a/docs/functions/index.md
+++ b/docs/functions/index.md
@@ -27,6 +27,7 @@ You can find documentation for every *public* function of WHY2 below.
 | Function                                                | Description                                      |
 | ------------------------------------------------------- | ------------------------------------------------ |
 | [`why2_sum_segment`](./core/crypto/why2_sum_segment.md) | Calculate SUM++ for input; Used for padding seed |
+| [`why2_random`](./core/crypto/why2_random.md)           | Write crypto-secure random number into dest      |
 
 ## Logger