diff --git a/substrate/primitives/runtime/src/lib.rs b/substrate/primitives/runtime/src/lib.rs
index 8f7bbf1680c0506fec8c7165f9958e9a926cd1cd..9bc23be1e975956f6ddcc341f48b7ff9250a6091 100644
--- a/substrate/primitives/runtime/src/lib.rs
+++ b/substrate/primitives/runtime/src/lib.rs
@@ -54,7 +54,6 @@ pub mod offchain;
pub mod testing;
pub mod traits;
pub mod transaction_validity;
-pub mod random_number_generator;
mod runtime_string;
mod multiaddress;
pub mod runtime_logger;
@@ -85,8 +84,6 @@ pub use sp_arithmetic::helpers_128bit;
/// Re-export big_uint stuff.
pub use sp_arithmetic::biguint;
-pub use random_number_generator::RandomNumberGenerator;
-
pub use either::Either;
/// An abstraction over justification for a block's validity under a consensus algorithm.
diff --git a/substrate/primitives/runtime/src/random_number_generator.rs b/substrate/primitives/runtime/src/random_number_generator.rs
deleted file mode 100644
index 0adf346579a903c4e642ff394eb02f6b78f312b8..0000000000000000000000000000000000000000
--- a/substrate/primitives/runtime/src/random_number_generator.rs
+++ /dev/null
@@ -1,118 +0,0 @@
-// This file is part of Substrate.
-
-// Copyright (C) 2017-2021 Parity Technologies (UK) Ltd.
-// SPDX-License-Identifier: Apache-2.0
-
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-//! A simple pseudo random number generator that allows a stream of random numbers to be efficiently
-//! created from a single initial seed hash.
-
-use codec::{Encode, Decode};
-use crate::traits::{Hash, TrailingZeroInput};
-
-/// Pseudo-random number streamer. This retains the state of the random number stream. It's as
-/// secure as the combination of the seed with which it is constructed and the hash function it uses
-/// to cycle elements.
-///
-/// It can be saved and later reloaded using the Codec traits.
-///
-/// (It is recommended to use the `rand_chacha` crate as an alternative to this where possible.)
-///
-/// Example:
-/// ```
-/// use sp_runtime::traits::{Hash, BlakeTwo256};
-/// use sp_runtime::RandomNumberGenerator;
-/// let random_seed = BlakeTwo256::hash(b"Sixty-nine");
-/// let mut rng = <RandomNumberGenerator<BlakeTwo256>>::new(random_seed);
-/// assert_eq!(rng.pick_u32(100), 59);
-/// assert_eq!(rng.pick_item(&[1, 2, 3]), Some(&1));
-/// ```
-///
-/// This can use any cryptographic `Hash` function as the means of entropy-extension, and avoids
-/// needless extensions of entropy.
-///
-/// If you're persisting it over blocks, be aware that the sequence will start to repeat. This won't
-/// be a practical issue unless you're using tiny hash types (e.g. 64-bit) and pulling hundred of
-/// megabytes of data from it.
-#[derive(Encode, Decode)]
-pub struct RandomNumberGenerator<Hashing: Hash> {
- current: Hashing::Output,
- offset: u32,
-}
-
-impl<Hashing: Hash> RandomNumberGenerator<Hashing> {
- /// A new source of random data.
- pub fn new(seed: Hashing::Output) -> Self {
- Self {
- current: seed,
- offset: 0,
- }
- }
-
- fn offset(&self) -> usize { self.offset as usize }
-
- /// Returns a number at least zero, at most `max`.
- pub fn pick_u32(&mut self, max: u32) -> u32 {
- let needed = (4 - max.leading_zeros() / 8) as usize;
- let top = ((1 << (needed as u64 * 8)) / (max as u64 + 1) * (max as u64 + 1) - 1) as u32;
- loop {
- if self.offset() + needed > self.current.as_ref().len() {
- // rehash
- self.current = <Hashing as Hash>::hash(self.current.as_ref());
- self.offset = 0;
- }
- let data = &self.current.as_ref()[self.offset()..self.offset() + needed];
- self.offset += needed as u32;
- let raw = u32::decode(&mut TrailingZeroInput::new(data)).unwrap_or(0);
- if raw <= top {
- break if max < u32::MAX {
- raw % (max + 1)
- } else {
- raw
- }
- }
- }
- }
-
- /// Returns a number at least zero, at most `max`.
- ///
- /// This returns a `usize`, but internally it only uses `u32` so avoid consensus problems.
- pub fn pick_usize(&mut self, max: usize) -> usize {
- self.pick_u32(max as u32) as usize
- }
-
- /// Pick a random element from an array of `items`.
- ///
- /// This is guaranteed to return `Some` except in the case that the given array `items` is
- /// empty.
- pub fn pick_item<'a, T>(&mut self, items: &'a [T]) -> Option<&'a T> {
- if items.is_empty() {
- None
- } else {
- Some(&items[self.pick_usize(items.len() - 1)])
- }
- }
-}
-
-#[cfg(test)]
-mod tests {
- use super::RandomNumberGenerator;
- use crate::traits::{Hash, BlakeTwo256};
-
- #[test]
- fn does_not_panic_on_max() {
- let seed = BlakeTwo256::hash(b"Fourty-two");
- let _random = RandomNumberGenerator::<BlakeTwo256>::new(seed).pick_u32(u32::MAX);
- }
-}