Update nitrokey crate to 0.4.0

This change finally updates the version of the nitrokey crate that we
consume to 0.4.0. Along with that we update rand_core, one of its
dependencies, to 0.5.1. Further more we add cfg-if in version 0.1.10 and
getrandom in version 0.1.13, both of which are now new (non-development)
dependencies.

Import subrepo nitrokey/:nitrokey at e81057037e9b4f370b64c0a030a725bc6bdfb870
Import subrepo cfg-if/:cfg-if at 4484a6faf816ff8058088ad857b0c6bb2f4b02b2
Import subrepo getrandom/:getrandom at d661aa7e1b8cc80b47dabe3d2135b3b47d2858af
Import subrepo rand/:rand at d877ed528248b52d947e0484364a4e1ae59ca502

1 files changed, 0 insertions, 885 deletions

diff --git a/rand/src/rngs/jitter.rs b/rand/src/rngs/jitter.rs
deleted file mode 100644
index 3e93477..0000000
--- a/rand/src/rngs/jitter.rs
+++ /dev/null
@@ -1,885 +0,0 @@
-// Copyright 2018 Developers of the Rand project.
-//
-// 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.
-//
-// Based on jitterentropy-library, http://www.chronox.de/jent.html.
-// Copyright Stephan Mueller <smueller@chronox.de>, 2014 - 2017.
-//
-// With permission from Stephan Mueller to relicense the Rust translation under
-// the MIT license.
-
-//! Non-physical true random number generator based on timing jitter.
-
-// Note: the C implementation of `Jitterentropy` relies on being compiled
-// without optimizations. This implementation goes through lengths to make the
-// compiler not optimize out code which does influence timing jitter, but is
-// technically dead code.
-
-use rand_core::{RngCore, CryptoRng, Error, ErrorKind, impls};
-
-use core::{fmt, mem, ptr};
-#[cfg(all(feature="std", not(target_arch = "wasm32")))]
-use std::sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
-
-const MEMORY_BLOCKS: usize = 64;
-const MEMORY_BLOCKSIZE: usize = 32;
-const MEMORY_SIZE: usize = MEMORY_BLOCKS * MEMORY_BLOCKSIZE;
-
-/// A true random number generator based on jitter in the CPU execution time,
-/// and jitter in memory access time.
-///
-/// This is a true random number generator, as opposed to pseudo-random
-/// generators. Random numbers generated by `JitterRng` can be seen as fresh
-/// entropy. A consequence is that is orders of magnitude slower than [`OsRng`]
-/// and PRNGs (about 10<sup>3</sup>..10<sup>6</sup> slower).
-///
-/// There are very few situations where using this RNG is appropriate. Only very
-/// few applications require true entropy. A normal PRNG can be statistically
-/// indistinguishable, and a cryptographic PRNG should also be as impossible to
-/// predict.
-///
-/// Use of `JitterRng` is recommended for initializing cryptographic PRNGs when
-/// [`OsRng`] is not available.
-///
-/// `JitterRng` can be used without the standard library, but not conveniently,
-/// you must provide a high-precision timer and carefully have to follow the
-/// instructions of [`new_with_timer`].
-///
-/// This implementation is based on
-/// [Jitterentropy](http://www.chronox.de/jent.html) version 2.1.0.
-///
-/// Note: There is no accurate timer available on Wasm platforms, to help
-/// prevent fingerprinting or timing side-channel attacks. Therefore
-/// [`JitterRng::new()`] is not available on Wasm.
-///
-/// # Quality testing
-///
-/// [`JitterRng::new()`] has build-in, but limited, quality testing, however
-/// before using `JitterRng` on untested hardware, or after changes that could
-/// effect how the code is optimized (such as a new LLVM version), it is
-/// recommend to run the much more stringent
-/// [NIST SP 800-90B Entropy Estimation Suite](
-/// https://github.com/usnistgov/SP800-90B_EntropyAssessment).
-///
-/// Use the following code using [`timer_stats`] to collect the data:
-///
-/// ```no_run
-/// use rand::rngs::JitterRng;
-/// #
-/// # use std::error::Error;
-/// # use std::fs::File;
-/// # use std::io::Write;
-/// #
-/// # fn try_main() -> Result<(), Box<Error>> {
-/// let mut rng = JitterRng::new()?;
-///
-/// // 1_000_000 results are required for the
-/// // NIST SP 800-90B Entropy Estimation Suite
-/// const ROUNDS: usize = 1_000_000;
-/// let mut deltas_variable: Vec<u8> = Vec::with_capacity(ROUNDS);
-/// let mut deltas_minimal: Vec<u8> = Vec::with_capacity(ROUNDS);
-///
-/// for _ in 0..ROUNDS {
-///     deltas_variable.push(rng.timer_stats(true) as u8);
-///     deltas_minimal.push(rng.timer_stats(false) as u8);
-/// }
-///
-/// // Write out after the statistics collection loop, to not disturb the
-/// // test results.
-/// File::create("jitter_rng_var.bin")?.write(&deltas_variable)?;
-/// File::create("jitter_rng_min.bin")?.write(&deltas_minimal)?;
-/// #
-/// # Ok(())
-/// # }
-/// #
-/// # fn main() {
-/// #     try_main().unwrap();
-/// # }
-/// ```
-///
-/// This will produce two files: `jitter_rng_var.bin` and `jitter_rng_min.bin`.
-/// Run the Entropy Estimation Suite in three configurations, as outlined below.
-/// Every run has two steps. One step to produce an estimation, another to
-/// validate the estimation.
-///
-/// 1. Estimate the expected amount of entropy that is at least available with
-///    each round of the entropy collector. This number should be greater than
-///    the amount estimated with `64 / test_timer()`.
-///    ```sh
-///    python noniid_main.py -v jitter_rng_var.bin 8
-///    restart.py -v jitter_rng_var.bin 8 <min-entropy>
-///    ```
-/// 2. Estimate the expected amount of entropy that is available in the last 4
-///    bits of the timer delta after running noice sources. Note that a value of
-///    `3.70` is the minimum estimated entropy for true randomness.
-///    ```sh
-///    python noniid_main.py -v -u 4 jitter_rng_var.bin 4
-///    restart.py -v -u 4 jitter_rng_var.bin 4 <min-entropy>
-///    ```
-/// 3. Estimate the expected amount of entropy that is available to the entropy
-///    collector if both noice sources only run their minimal number of times.
-///    This measures the absolute worst-case, and gives a lower bound for the
-///    available entropy.
-///    ```sh
-///    python noniid_main.py -v -u 4 jitter_rng_min.bin 4
-///    restart.py -v -u 4 jitter_rng_min.bin 4 <min-entropy>
-///    ```
-///
-/// [`OsRng`]: struct.OsRng.html
-/// [`JitterRng::new()`]: struct.JitterRng.html#method.new
-/// [`new_with_timer`]: struct.JitterRng.html#method.new_with_timer
-/// [`timer_stats`]: struct.JitterRng.html#method.timer_stats
-pub struct JitterRng {
-    data: u64, // Actual random number
-    // Number of rounds to run the entropy collector per 64 bits
-    rounds: u8,
-    // Timer used by `measure_jitter`
-    timer: fn() -> u64,
-    // Memory for the Memory Access noise source
-    mem_prev_index: u16,
-    // Make `next_u32` not waste 32 bits
-    data_half_used: bool,
-}
-
-// Note: `JitterRng` maintains a small 64-bit entropy pool. With every
-// `generate` 64 new bits should be integrated in the pool. If a round of
-// `generate` were to collect less than the expected 64 bit, then the returned
-// value, and the new state of the entropy pool, would be in some way related to
-// the initial state. It is therefore better if the initial state of the entropy
-// pool is different on each call to `generate`. This has a few implications:
-// - `generate` should be called once before using `JitterRng` to produce the
-//   first usable value (this is done by default in `new`);
-// - We do not zero the entropy pool after generating a result. The reference
-//   implementation also does not support zeroing, but recommends generating a
-//   new value without using it if you want to protect a previously generated
-//   'secret' value from someone inspecting the memory;
-// - Implementing `Clone` seems acceptable, as it would not cause the systematic
-//   bias a constant might cause. Only instead of one value that could be
-//   potentially related to the same initial state, there are now two.
-
-// Entropy collector state.
-// These values are not necessary to preserve across runs.
-struct EcState {
-    // Previous time stamp to determine the timer delta
-    prev_time: u64,
-    // Deltas used for the stuck test
-    last_delta: i32,
-    last_delta2: i32,
-    // Memory for the Memory Access noise source
-    mem: [u8; MEMORY_SIZE],
-}
-
-impl EcState {
-    // Stuck test by checking the:
-    // - 1st derivation of the jitter measurement (time delta)
-    // - 2nd derivation of the jitter measurement (delta of time deltas)
-    // - 3rd derivation of the jitter measurement (delta of delta of time
-    //   deltas)
-    //
-    // All values must always be non-zero.
-    // This test is a heuristic to see whether the last measurement holds
-    // entropy.
-    fn stuck(&mut self, current_delta: i32) -> bool {
-        let delta2 = self.last_delta - current_delta;
-        let delta3 = delta2 - self.last_delta2;
-
-        self.last_delta = current_delta;
-        self.last_delta2 = delta2;
-
-        current_delta == 0 || delta2 == 0 || delta3 == 0
-    }
-}
-
-// Custom Debug implementation that does not expose the internal state
-impl fmt::Debug for JitterRng {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "JitterRng {{}}")
-    }
-}
-
-impl Clone for JitterRng {
-    fn clone(&self) -> JitterRng {
-        JitterRng {
-            data: self.data,
-            rounds: self.rounds,
-            timer: self.timer,
-            mem_prev_index: self.mem_prev_index,
-            // The 32 bits that may still be unused from the previous round are
-            // for the original to use, not for the clone.
-            data_half_used: false,
-        }
-    }
-}
-
-/// An error that can occur when [`JitterRng::test_timer`] fails.
-///
-/// [`JitterRng::test_timer`]: struct.JitterRng.html#method.test_timer
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum TimerError {
-    /// No timer available.
-    NoTimer,
-    /// Timer too coarse to use as an entropy source.
-    CoarseTimer,
-    /// Timer is not monotonically increasing.
-    NotMonotonic,
-    /// Variations of deltas of time too small.
-    TinyVariantions,
-    /// Too many stuck results (indicating no added entropy).
-    TooManyStuck,
-    #[doc(hidden)]
-    __Nonexhaustive,
-}
-
-impl TimerError {
-    fn description(&self) -> &'static str {
-        match *self {
-            TimerError::NoTimer => "no timer available",
-            TimerError::CoarseTimer => "coarse timer",
-            TimerError::NotMonotonic => "timer not monotonic",
-            TimerError::TinyVariantions => "time delta variations too small",
-            TimerError::TooManyStuck => "too many stuck results",
-            TimerError::__Nonexhaustive => unreachable!(),
-        }
-    }
-}
-
-impl fmt::Display for TimerError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", self.description())
-    }
-}
-
-#[cfg(feature="std")]
-impl ::std::error::Error for TimerError {
-    fn description(&self) -> &str {
-        self.description()
-    }
-}
-
-impl From<TimerError> for Error {
-    fn from(err: TimerError) -> Error {
-        // Timer check is already quite permissive of failures so we don't
-        // expect false-positive failures, i.e. any error is irrecoverable.
-        Error::with_cause(ErrorKind::Unavailable,
-                              "timer jitter failed basic quality tests", err)
-    }
-}
-
-// Initialise to zero; must be positive
-#[cfg(all(feature="std", not(target_arch = "wasm32")))]
-static JITTER_ROUNDS: AtomicUsize = ATOMIC_USIZE_INIT;
-
-impl JitterRng {
-    /// Create a new `JitterRng`. Makes use of `std::time` for a timer, or a
-    /// platform-specific function with higher accuracy if necessary and
-    /// available.
-    ///
-    /// During initialization CPU execution timing jitter is measured a few
-    /// hundred times. If this does not pass basic quality tests, an error is
-    /// returned. The test result is cached to make subsequent calls faster.
-    #[cfg(all(feature="std", not(target_arch = "wasm32")))]
-    pub fn new() -> Result<JitterRng, TimerError> {
-        let mut state = JitterRng::new_with_timer(platform::get_nstime);
-        let mut rounds = JITTER_ROUNDS.load(Ordering::Relaxed) as u8;
-        if rounds == 0 {
-            // No result yet: run test.
-            // This allows the timer test to run multiple times; we don't care.
-            rounds = state.test_timer()?;
-            JITTER_ROUNDS.store(rounds as usize, Ordering::Relaxed);
-            info!("JitterRng: using {} rounds per u64 output", rounds);
-        }
-        state.set_rounds(rounds);
-
-        // Fill `data` with a non-zero value.
-        state.gen_entropy();
-        Ok(state)
-    }
-
-    /// Create a new `JitterRng`.
-    /// A custom timer can be supplied, making it possible to use `JitterRng` in
-    /// `no_std` environments.
-    ///
-    /// The timer must have nanosecond precision.
-    ///
-    /// This method is more low-level than `new()`. It is the responsibility of
-    /// the caller to run [`test_timer`] before using any numbers generated with
-    /// `JitterRng`, and optionally call [`set_rounds`]. Also it is important to
-    /// consume at least one `u64` before using the first result to initialize
-    /// the entropy collection pool.
-    ///
-    /// # Example
-    ///
-    /// ```
-    /// # use rand::{Rng, Error};
-    /// use rand::rngs::JitterRng;
-    ///
-    /// # fn try_inner() -> Result<(), Error> {
-    /// fn get_nstime() -> u64 {
-    ///     use std::time::{SystemTime, UNIX_EPOCH};
-    ///
-    ///     let dur = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
-    ///     // The correct way to calculate the current time is
-    ///     // `dur.as_secs() * 1_000_000_000 + dur.subsec_nanos() as u64`
-    ///     // But this is faster, and the difference in terms of entropy is
-    ///     // negligible (log2(10^9) == 29.9).
-    ///     dur.as_secs() << 30 | dur.subsec_nanos() as u64
-    /// }
-    ///
-    /// let mut rng = JitterRng::new_with_timer(get_nstime);
-    /// let rounds = rng.test_timer()?;
-    /// rng.set_rounds(rounds); // optional
-    /// let _ = rng.gen::<u64>();
-    ///
-    /// // Ready for use
-    /// let v: u64 = rng.gen();
-    /// # Ok(())
-    /// # }
-    ///
-    /// # let _ = try_inner();
-    /// ```
-    ///
-    /// [`test_timer`]: struct.JitterRng.html#method.test_timer
-    /// [`set_rounds`]: struct.JitterRng.html#method.set_rounds
-    pub fn new_with_timer(timer: fn() -> u64) -> JitterRng {
-        JitterRng {
-            data: 0,
-            rounds: 64,
-            timer,
-            mem_prev_index: 0,
-            data_half_used: false,
-        }
-    }
-
-    /// Configures how many rounds are used to generate each 64-bit value.
-    /// This must be greater than zero, and has a big impact on performance
-    /// and output quality.
-    ///
-    /// [`new_with_timer`] conservatively uses 64 rounds, but often less rounds
-    /// can be used. The `test_timer()` function returns the minimum number of
-    /// rounds required for full strength (platform dependent), so one may use
-    /// `rng.set_rounds(rng.test_timer()?);` or cache the value.
-    ///
-    /// [`new_with_timer`]: struct.JitterRng.html#method.new_with_timer
-    pub fn set_rounds(&mut self, rounds: u8) {
-        assert!(rounds > 0);
-        self.rounds = rounds;
-    }
-
-    // Calculate a random loop count used for the next round of an entropy
-    // collection, based on bits from a fresh value from the timer.
-    //
-    // The timer is folded to produce a number that contains at most `n_bits`
-    // bits.
-    //
-    // Note: A constant should be added to the resulting random loop count to
-    // prevent loops that run 0 times.
-    #[inline(never)]
-    fn random_loop_cnt(&mut self, n_bits: u32) -> u32 {
-        let mut rounds = 0;
-
-        let mut time = (self.timer)();
-        // Mix with the current state of the random number balance the random
-        // loop counter a bit more.
-        time ^= self.data;
-
-        // We fold the time value as much as possible to ensure that as many
-        // bits of the time stamp are included as possible.
-        let folds = (64 + n_bits - 1) / n_bits;
-        let mask = (1 << n_bits) - 1;
-        for _ in 0..folds {
-            rounds ^= time & mask;
-            time >>= n_bits;
-        }
-
-        rounds as u32
-    }
-
-    // CPU jitter noise source
-    // Noise source based on the CPU execution time jitter
-    //
-    // This function injects the individual bits of the time value into the
-    // entropy pool using an LFSR.
-    //
-    // The code is deliberately inefficient with respect to the bit shifting.
-    // This function not only acts as folding operation, but this function's
-    // execution is used to measure the CPU execution time jitter. Any change to
-    // the loop in this function implies that careful retesting must be done.
-    #[inline(never)]
-    fn lfsr_time(&mut self, time: u64, var_rounds: bool) {
-        fn lfsr(mut data: u64, time: u64) -> u64{
-            for i in 1..65 {
-                let mut tmp = time << (64 - i);
-                tmp >>= 64 - 1;
-
-                // Fibonacci LSFR with polynomial of
-                // x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is
-                // primitive according to
-                // http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf
-                // (the shift values are the polynomial values minus one
-                // due to counting bits from 0 to 63). As the current
-                // position is always the LSB, the polynomial only needs
-                // to shift data in from the left without wrap.
-                data ^= tmp;
-                data ^= (data >> 63) & 1;
-                data ^= (data >> 60) & 1;
-                data ^= (data >> 55) & 1;
-                data ^= (data >> 30) & 1;
-                data ^= (data >> 27) & 1;
-                data ^= (data >> 22) & 1;
-                data = data.rotate_left(1);
-            }
-            data
-        }
-
-        // Note: in the reference implementation only the last round effects
-        // `self.data`, all the other results are ignored. To make sure the
-        // other rounds are not optimised out, we first run all but the last
-        // round on a throw-away value instead of the real `self.data`.
-        let mut lfsr_loop_cnt = 0;
-        if var_rounds { lfsr_loop_cnt = self.random_loop_cnt(4) };
-
-        let mut throw_away: u64 = 0;
-        for _ in 0..lfsr_loop_cnt {
-            throw_away = lfsr(throw_away, time);
-        }
-        black_box(throw_away);
-
-        self.data = lfsr(self.data, time);
-    }
-
-    // Memory Access noise source
-    // This is a noise source based on variations in memory access times
-    //
-    // This function performs memory accesses which will add to the timing
-    // variations due to an unknown amount of CPU wait states that need to be
-    // added when accessing memory. The memory size should be larger than the L1
-    // caches as outlined in the documentation and the associated testing.
-    //
-    // The L1 cache has a very high bandwidth, albeit its access rate is usually
-    // slower than accessing CPU registers. Therefore, L1 accesses only add
-    // minimal variations as the CPU has hardly to wait. Starting with L2,
-    // significant variations are added because L2 typically does not belong to
-    // the CPU any more and therefore a wider range of CPU wait states is
-    // necessary for accesses. L3 and real memory accesses have even a wider
-    // range of wait states. However, to reliably access either L3 or memory,
-    // the `self.mem` memory must be quite large which is usually not desirable.
-    #[inline(never)]
-    fn memaccess(&mut self, mem: &mut [u8; MEMORY_SIZE], var_rounds: bool) {
-        let mut acc_loop_cnt = 128;
-        if var_rounds { acc_loop_cnt += self.random_loop_cnt(4) };
-
-        let mut index = self.mem_prev_index as usize;
-        for _ in 0..acc_loop_cnt {
-            // Addition of memblocksize - 1 to index with wrap around logic to
-            // ensure that every memory location is hit evenly.
-            // The modulus also allows the compiler to remove the indexing
-            // bounds check.
-            index = (index + MEMORY_BLOCKSIZE - 1) % MEMORY_SIZE;
-
-            // memory access: just add 1 to one byte
-            // memory access implies read from and write to memory location
-            mem[index] = mem[index].wrapping_add(1);
-        }
-        self.mem_prev_index = index as u16;
-    }
-
-    // This is the heart of the entropy generation: calculate time deltas and
-    // use the CPU jitter in the time deltas. The jitter is injected into the
-    // entropy pool.
-    //
-    // Ensure that `ec.prev_time` is primed before using the output of this
-    // function. This can be done by calling this function and not using its
-    // result.
-    fn measure_jitter(&mut self, ec: &mut EcState) -> Option<()> {
-        // Invoke one noise source before time measurement to add variations
-        self.memaccess(&mut ec.mem, true);
-
-        // Get time stamp and calculate time delta to previous
-        // invocation to measure the timing variations
-        let time = (self.timer)();
-        // Note: wrapping_sub combined with a cast to `i64` generates a correct
-        // delta, even in the unlikely case this is a timer that is not strictly
-        // monotonic.
-        let current_delta = time.wrapping_sub(ec.prev_time) as i64 as i32;
-        ec.prev_time = time;
-
-        // Call the next noise source which also injects the data
-        self.lfsr_time(current_delta as u64, true);
-
-        // Check whether we have a stuck measurement (i.e. does the last
-        // measurement holds entropy?).
-        if ec.stuck(current_delta) { return None };
-
-        // Rotate the data buffer by a prime number (any odd number would
-        // do) to ensure that every bit position of the input time stamp
-        // has an even chance of being merged with a bit position in the
-        // entropy pool. We do not use one here as the adjacent bits in
-        // successive time deltas may have some form of dependency. The
-        // chosen value of 7 implies that the low 7 bits of the next
-        // time delta value is concatenated with the current time delta.
-        self.data = self.data.rotate_left(7);
-
-        Some(())
-    }
-
-    // Shuffle the pool a bit by mixing some value with a bijective function
-    // (XOR) into the pool.
-    //
-    // The function generates a mixer value that depends on the bits set and
-    // the location of the set bits in the random number generated by the
-    // entropy source. Therefore, based on the generated random number, this
-    // mixer value can have 2^64 different values. That mixer value is
-    // initialized with the first two SHA-1 constants. After obtaining the
-    // mixer value, it is XORed into the random number.
-    //
-    // The mixer value is not assumed to contain any entropy. But due to the
-    // XOR operation, it can also not destroy any entropy present in the
-    // entropy pool.
-    #[inline(never)]
-    fn stir_pool(&mut self) {
-        // This constant is derived from the first two 32 bit initialization
-        // vectors of SHA-1 as defined in FIPS 180-4 section 5.3.1
-        // The order does not really matter as we do not rely on the specific
-        // numbers. We just pick the SHA-1 constants as they have a good mix of
-        // bit set and unset.
-        const CONSTANT: u64 = 0x67452301efcdab89;
-
-        // The start value of the mixer variable is derived from the third
-        // and fourth 32 bit initialization vector of SHA-1 as defined in
-        // FIPS 180-4 section 5.3.1
-        let mut mixer = 0x98badcfe10325476;
-
-        // This is a constant time function to prevent leaking timing
-        // information about the random number.
-        // The normal code is:
-        // ```
-        // for i in 0..64 {
-        //     if ((self.data >> i) & 1) == 1 { mixer ^= CONSTANT; }
-        // }
-        // ```
-        // This is a bit fragile, as LLVM really wants to use branches here, and
-        // we rely on it to not recognise the opportunity.
-        for i in 0..64 {
-            let apply = (self.data >> i) & 1;
-            let mask = !apply.wrapping_sub(1);
-            mixer ^= CONSTANT & mask;
-            mixer = mixer.rotate_left(1);
-        }
-
-        self.data ^= mixer;
-    }
-
-    fn gen_entropy(&mut self) -> u64 {
-        trace!("JitterRng: collecting entropy");
-
-        // Prime `ec.prev_time`, and run the noice sources to make sure the
-        // first loop round collects the expected entropy.
-        let mut ec = EcState {
-            prev_time: (self.timer)(),
-            last_delta: 0,
-            last_delta2: 0,
-            mem: [0; MEMORY_SIZE],
-        };
-        let _ = self.measure_jitter(&mut ec);
-
-        for _ in 0..self.rounds {
-            // If a stuck measurement is received, repeat measurement
-            // Note: we do not guard against an infinite loop, that would mean
-            // the timer suddenly became broken.
-            while self.measure_jitter(&mut ec).is_none() {}
-        }
-
-        // Do a single read from `self.mem` to make sure the Memory Access noise
-        // source is not optimised out.
-        black_box(ec.mem[0]);
-
-        self.stir_pool();
-        self.data
-    }
-    
-    /// Basic quality tests on the timer, by measuring CPU timing jitter a few
-    /// hundred times.
-    ///
-    /// If succesful, this will return the estimated number of rounds necessary
-    /// to collect 64 bits of entropy. Otherwise a [`TimerError`] with the cause
-    /// of the failure will be returned.
-    ///
-    /// [`TimerError`]: enum.TimerError.html
-    pub fn test_timer(&mut self) -> Result<u8, TimerError> {
-        debug!("JitterRng: testing timer ...");
-        // We could add a check for system capabilities such as `clock_getres`
-        // or check for `CONFIG_X86_TSC`, but it does not make much sense as the
-        // following sanity checks verify that we have a high-resolution timer.
-
-        let mut delta_sum = 0;
-        let mut old_delta = 0;
-
-        let mut time_backwards = 0;
-        let mut count_mod = 0;
-        let mut count_stuck = 0;
-
-        let mut ec = EcState {
-            prev_time: (self.timer)(),
-            last_delta: 0,
-            last_delta2: 0,
-            mem: [0; MEMORY_SIZE],
-        };
-
-        // TESTLOOPCOUNT needs some loops to identify edge systems.
-        // 100 is definitely too little.
-        const TESTLOOPCOUNT: u64 = 300;
-        const CLEARCACHE: u64 = 100;
-
-        for i in 0..(CLEARCACHE + TESTLOOPCOUNT) {
-            // Measure time delta of core entropy collection logic
-            let time = (self.timer)();
-            self.memaccess(&mut ec.mem, true);
-            self.lfsr_time(time, true);
-            let time2 = (self.timer)();
-
-            // Test whether timer works
-            if time == 0 || time2 == 0 {
-                return Err(TimerError::NoTimer);
-            }
-            let delta = time2.wrapping_sub(time) as i64 as i32;
-
-            // Test whether timer is fine grained enough to provide delta even
-            // when called shortly after each other -- this implies that we also
-            // have a high resolution timer
-            if delta == 0 {
-                return Err(TimerError::CoarseTimer);
-            }
-
-            // Up to here we did not modify any variable that will be
-            // evaluated later, but we already performed some work. Thus we
-            // already have had an impact on the caches, branch prediction,
-            // etc. with the goal to clear it to get the worst case
-            // measurements.
-            if i < CLEARCACHE { continue; }
-
-            if ec.stuck(delta) { count_stuck += 1; }
-
-            // Test whether we have an increasing timer.
-            if !(time2 > time) { time_backwards += 1; }
-
-            // Count the number of times the counter increases in steps of 100ns
-            // or greater.
-            if (delta % 100) == 0 { count_mod += 1; }
-
-            // Ensure that we have a varying delta timer which is necessary for
-            // the calculation of entropy -- perform this check only after the
-            // first loop is executed as we need to prime the old_delta value
-            delta_sum += (delta - old_delta).abs() as u64;
-            old_delta = delta;
-        }
-
-        // Do a single read from `self.mem` to make sure the Memory Access noise
-        // source is not optimised out.
-        black_box(ec.mem[0]);
-
-        // We allow the time to run backwards for up to three times.
-        // This can happen if the clock is being adjusted by NTP operations.
-        // If such an operation just happens to interfere with our test, it
-        // should not fail. The value of 3 should cover the NTP case being
-        // performed during our test run.
-        if time_backwards > 3 {
-            return Err(TimerError::NotMonotonic);
-        }
-
-        // Test that the available amount of entropy per round does not get to
-        // low. We expect 1 bit of entropy per round as a reasonable minimum
-        // (although less is possible, it means the collector loop has to run
-        // much more often).
-        // `assert!(delta_average >= log2(1))`
-        // `assert!(delta_sum / TESTLOOPCOUNT >= 1)`
-        // `assert!(delta_sum >= TESTLOOPCOUNT)`
-        if delta_sum < TESTLOOPCOUNT {
-            return Err(TimerError::TinyVariantions);
-        }
-
-        // Ensure that we have variations in the time stamp below 100 for at
-        // least 10% of all checks -- on some platforms, the counter increments
-        // in multiples of 100, but not always
-        if count_mod > (TESTLOOPCOUNT * 9 / 10) {
-            return Err(TimerError::CoarseTimer);
-        }
-
-        // If we have more than 90% stuck results, then this Jitter RNG is
-        // likely to not work well.
-        if count_stuck > (TESTLOOPCOUNT * 9 / 10) {
-            return Err(TimerError::TooManyStuck);
-        }
-
-        // Estimate the number of `measure_jitter` rounds necessary for 64 bits
-        // of entropy.
-        //
-        // We don't try very hard to come up with a good estimate of the
-        // available bits of entropy per round here for two reasons:
-        // 1. Simple estimates of the available bits (like Shannon entropy) are
-        //    too optimistic.
-        // 2. Unless we want to waste a lot of time during intialization, there
-        //    only a small number of samples are available.
-        //
-        // Therefore we use a very simple and conservative estimate:
-        // `let bits_of_entropy = log2(delta_average) / 2`.
-        //
-        // The number of rounds `measure_jitter` should run to collect 64 bits
-        // of entropy is `64 / bits_of_entropy`.
-        let delta_average = delta_sum / TESTLOOPCOUNT;
-
-        if delta_average >= 16 {
-            let log2 = 64 - delta_average.leading_zeros();
-            // Do something similar to roundup(64/(log2/2)):
-            Ok( ((64u32 * 2 + log2 - 1) / log2) as u8)
-        } else {
-            // For values < 16 the rounding error becomes too large, use a
-            // lookup table.
-            // Values 0 and 1 are invalid, and filtered out by the
-            // `delta_sum < TESTLOOPCOUNT` test above.
-            let log2_lookup = [0,  0, 128, 81, 64, 56, 50, 46,
-                               43, 41, 39, 38, 36, 35, 34, 33];
-            Ok(log2_lookup[delta_average as usize])
-        }
-    }
-
-    /// Statistical test: return the timer delta of one normal run of the
-    /// `JitterRng` entropy collector.
-    ///
-    /// Setting `var_rounds` to `true` will execute the memory access and the
-    /// CPU jitter noice sources a variable amount of times (just like a real
-    /// `JitterRng` round).
-    ///
-    /// Setting `var_rounds` to `false` will execute the noice sources the
-    /// minimal number of times. This can be used to measure the minimum amount
-    /// of entropy one round of the entropy collector can collect in the worst
-    /// case.
-    ///
-    /// See [Quality testing](struct.JitterRng.html#quality-testing) on how to
-    /// use `timer_stats` to test the quality of `JitterRng`.
-    pub fn timer_stats(&mut self, var_rounds: bool) -> i64 {
-        let mut mem = [0; MEMORY_SIZE];
-
-        let time = (self.timer)();
-        self.memaccess(&mut mem, var_rounds);
-        self.lfsr_time(time, var_rounds);
-        let time2 = (self.timer)();
-        time2.wrapping_sub(time) as i64
-    }
-}
-
-#[cfg(feature="std")]
-mod platform {
-    #[cfg(not(any(target_os = "macos", target_os = "ios",
-                  target_os = "windows",
-                  target_arch = "wasm32")))]
-    pub fn get_nstime() -> u64 {
-        use std::time::{SystemTime, UNIX_EPOCH};
-
-        let dur = SystemTime::now().duration_since(UNIX_EPOCH).unwrap();
-        // The correct way to calculate the current time is
-        // `dur.as_secs() * 1_000_000_000 + dur.subsec_nanos() as u64`
-        // But this is faster, and the difference in terms of entropy is
-        // negligible (log2(10^9) == 29.9).
-        dur.as_secs() << 30 | dur.subsec_nanos() as u64
-    }
-
-    #[cfg(any(target_os = "macos", target_os = "ios"))]
-    pub fn get_nstime() -> u64 {
-        extern crate libc;
-        // On Mac OS and iOS std::time::SystemTime only has 1000ns resolution.
-        // We use `mach_absolute_time` instead. This provides a CPU dependent
-        // unit, to get real nanoseconds the result should by multiplied by
-        // numer/denom from `mach_timebase_info`.
-        // But we are not interested in the exact nanoseconds, just entropy. So
-        // we use the raw result.
-        unsafe { libc::mach_absolute_time() }
-    }
-
-    #[cfg(target_os = "windows")]
-    pub fn get_nstime() -> u64 {
-        extern crate winapi;
-        unsafe {
-            let mut t = super::mem::zeroed();
-            winapi::um::profileapi::QueryPerformanceCounter(&mut t);
-            *t.QuadPart() as u64
-        }
-    }
-}
-
-// A function that is opaque to the optimizer to assist in avoiding dead-code
-// elimination. Taken from `bencher`.
-fn black_box<T>(dummy: T) -> T {
-    unsafe {
-        let ret = ptr::read_volatile(&dummy);
-        mem::forget(dummy);
-        ret
-    }
-}
-
-impl RngCore for JitterRng {
-    fn next_u32(&mut self) -> u32 {
-        // We want to use both parts of the generated entropy
-        if self.data_half_used {
-            self.data_half_used = false;
-            (self.data >> 32) as u32
-        } else {
-            self.data = self.next_u64();
-            self.data_half_used = true;
-            self.data as u32
-        }
-    }
-
-    fn next_u64(&mut self) -> u64 {
-       self.data_half_used = false;
-       self.gen_entropy()
-    }
-
-    fn fill_bytes(&mut self, dest: &mut [u8]) {
-        // Fill using `next_u32`. This is faster for filling small slices (four
-        // bytes or less), while the overhead is negligible.
-        //
-        // This is done especially for wrappers that implement `next_u32`
-        // themselves via `fill_bytes`.
-        impls::fill_bytes_via_next(self, dest)
-    }
-
-    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
-        Ok(self.fill_bytes(dest))
-    }
-}
-
-impl CryptoRng for JitterRng {}
-
-#[cfg(test)]
-mod test_jitter_init {
-    use super::JitterRng;
-
-    #[cfg(all(feature="std", not(target_arch = "wasm32")))]
-    #[test]
-    fn test_jitter_init() {
-        use RngCore;
-        // Because this is a debug build, measurements here are not representive
-        // of the final release build.
-        // Don't fail this test if initializing `JitterRng` fails because of a
-        // bad timer (the timer from the standard library may not have enough
-        // accuracy on all platforms).
-        match JitterRng::new() {
-            Ok(ref mut rng) => {
-                // false positives are possible, but extremely unlikely
-                assert!(rng.next_u32() | rng.next_u32() != 0);
-            },
-            Err(_) => {},
-        }
-    }
-
-    #[test]
-    fn test_jitter_bad_timer() {
-        fn bad_timer() -> u64 { 0 }
-        let mut rng = JitterRng::new_with_timer(bad_timer);
-        assert!(rng.test_timer().is_err());
-    }
-}