Add nitrokey as a dependency to nitrocli

The nitrokey crate provides a simple interface to the Nitrokey Storage
and the Nitrokey Pro based on the libnitrokey library developed by
Nitrokey UG.  The low-level bindings to this library are available in
the nitrokey-sys crate.

This patch adds version v0.2.1 of the nitrokey crate as a dependency
for nitrocli.  It includes the indirect dependencies nitrokey-sys
(version 3.4.1) and rand (version 0.4.3).

Import subrepo nitrokey/:nitrokey at 2eccc96ceec2282b868891befe9cda7f941fbe7b
Import subrepo nitrokey-sys/:nitrokey-sys at f1a11ebf72610fb9cf80ac7f9f147b4ba1a5336f
Import subrepo rand/:rand at d7d5da49daf7ceb3e5940072940d495cced3a1b3

1 files changed, 51 insertions, 0 deletions

diff --git a/rand/src/prng/mod.rs b/rand/src/prng/mod.rs
new file mode 100644
index 0000000..ed3e018
--- /dev/null
+++ b/rand/src/prng/mod.rs
@@ -0,0 +1,51 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Pseudo random number generators are algorithms to produce *apparently
+//! random* numbers deterministically, and usually fairly quickly.
+//! 
+//! So long as the algorithm is computationally secure, is initialised with
+//! sufficient entropy (i.e. unknown by an attacker), and its internal state is
+//! also protected (unknown to an attacker), the output will also be
+//! *computationally secure*. Computationally Secure Pseudo Random Number
+//! Generators (CSPRNGs) are thus suitable sources of random numbers for
+//! cryptography. There are a couple of gotchas here, however. First, the seed
+//! used for initialisation must be unknown. Usually this should be provided by
+//! the operating system and should usually be secure, however this may not
+//! always be the case (especially soon after startup). Second, user-space
+//! memory may be vulnerable, for example when written to swap space, and after
+//! forking a child process should reinitialise any user-space PRNGs. For this
+//! reason it may be preferable to source random numbers directly from the OS
+//! for cryptographic applications.
+//! 
+//! PRNGs are also widely used for non-cryptographic uses: randomised
+//! algorithms, simulations, games. In these applications it is usually not
+//! important for numbers to be cryptographically *unguessable*, but even
+//! distribution and independence from other samples (from the point of view
+//! of someone unaware of the algorithm used, at least) may still be important.
+//! Good PRNGs should satisfy these properties, but do not take them for
+//! granted; Wikipedia's article on 
+//! [Pseudorandom number generators](https://en.wikipedia.org/wiki/Pseudorandom_number_generator)
+//! provides some background on this topic.
+//! 
+//! Care should be taken when seeding (initialising) PRNGs. Some PRNGs have
+//! short periods for some seeds. If one PRNG is seeded from another using the
+//! same algorithm, it is possible that both will yield the same sequence of
+//! values (with some lag).
+
+mod chacha;
+mod isaac;
+mod isaac64;
+mod xorshift;
+
+pub use self::chacha::ChaChaRng;
+pub use self::isaac::IsaacRng;
+pub use self::isaac64::Isaac64Rng;
+pub use self::xorshift::XorShiftRng;