Update nitrokey crate to 0.2.3

This change updates the nitrokey crate to version 0.2.3. This version
bumps the rand crate used to 0.6.1, which in turn requires an additional
set of dependencies.

Import subrepo nitrokey/:nitrokey at b3e2adc5bb1300441ca74cc7672617c042f3ea31
Import subrepo rand/:rand at 73613ff903512e9503e41cc8ba9eae76269dc598
Import subrepo rustc_version/:rustc_version at 0294f2ba2018bf7be672abd53db351ce5055fa02
Import subrepo semver-parser/:semver-parser at 750da9b11a04125231b1fb293866ca036845acee
Import subrepo semver/:semver at 5eb6db94fa03f4d5c64a625a56188f496be47598

1 files changed, 115 insertions, 0 deletions

diff --git a/rand/src/distributions/cauchy.rs b/rand/src/distributions/cauchy.rs
new file mode 100644
index 0000000..feef015
--- /dev/null
+++ b/rand/src/distributions/cauchy.rs
@@ -0,0 +1,115 @@
+// Copyright 2018 Developers of the Rand project.
+// Copyright 2016-2017 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! The Cauchy distribution.
+
+use Rng;
+use distributions::Distribution;
+use std::f64::consts::PI;
+
+/// The Cauchy distribution `Cauchy(median, scale)`.
+///
+/// This distribution has a density function:
+/// `f(x) = 1 / (pi * scale * (1 + ((x - median) / scale)^2))`
+///
+/// # Example
+///
+/// ```
+/// use rand::distributions::{Cauchy, Distribution};
+///
+/// let cau = Cauchy::new(2.0, 5.0);
+/// let v = cau.sample(&mut rand::thread_rng());
+/// println!("{} is from a Cauchy(2, 5) distribution", v);
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Cauchy {
+    median: f64,
+    scale: f64
+}
+
+impl Cauchy {
+    /// Construct a new `Cauchy` with the given shape parameters
+    /// `median` the peak location and `scale` the scale factor.
+    /// Panics if `scale <= 0`.
+    pub fn new(median: f64, scale: f64) -> Cauchy {
+        assert!(scale > 0.0, "Cauchy::new called with scale factor <= 0");
+        Cauchy {
+            median,
+            scale
+        }
+    }
+}
+
+impl Distribution<f64> for Cauchy {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
+        // sample from [0, 1)
+        let x = rng.gen::<f64>();
+        // get standard cauchy random number
+        // note that π/2 is not exactly representable, even if x=0.5 the result is finite
+        let comp_dev = (PI * x).tan();
+        // shift and scale according to parameters
+        let result = self.median + self.scale * comp_dev;
+        result
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use distributions::Distribution;
+    use super::Cauchy;
+
+    fn median(mut numbers: &mut [f64]) -> f64 {
+        sort(&mut numbers);
+        let mid = numbers.len() / 2;
+        numbers[mid]
+    }
+
+    fn sort(numbers: &mut [f64]) {
+        numbers.sort_by(|a, b| a.partial_cmp(b).unwrap());
+    }
+
+    #[test]
+    fn test_cauchy_median() {
+        let cauchy = Cauchy::new(10.0, 5.0);
+        let mut rng = ::test::rng(123);
+        let mut numbers: [f64; 1000] = [0.0; 1000];
+        for i in 0..1000 {
+            numbers[i] = cauchy.sample(&mut rng);
+        }
+        let median = median(&mut numbers);
+        println!("Cauchy median: {}", median);
+        assert!((median - 10.0).abs() < 0.5); // not 100% certain, but probable enough
+    }
+
+    #[test]
+    fn test_cauchy_mean() {
+        let cauchy = Cauchy::new(10.0, 5.0);
+        let mut rng = ::test::rng(123);
+        let mut sum = 0.0;
+        for _ in 0..1000 {
+            sum += cauchy.sample(&mut rng);
+        }
+        let mean = sum / 1000.0;
+        println!("Cauchy mean: {}", mean);
+        // for a Cauchy distribution the mean should not converge
+        assert!((mean - 10.0).abs() > 0.5); // not 100% certain, but probable enough
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_cauchy_invalid_scale_zero() {
+        Cauchy::new(0.0, 0.0);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_cauchy_invalid_scale_neg() {
+        Cauchy::new(0.0, -10.0);
+    }
+}