1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189

#![doc = include_str!("../README.md")]

//! ## Usage
//!
//! This crate defines a [`UInt`] type which is const generic around an inner
//! [`Limb`] array, where a [`Limb`] is a newtype for a word-sized integer.
//! Thus large integers are represented as a arrays of smaller integers which
//! are sized appropriately for the CPU, giving us some assurances of how
//! arithmetic operations over those smaller integers will behave.
//!
//! To obtain appropriately sized integers regardless of what a given CPU's
//! word size happens to be, a number of portable type aliases are provided for
//! integer sizes commonly used in cryptography, for example:
//! [`U128`], [`U384`], [`U256`], [`U2048`], [`U3072`], [`U4096`].
//!
//! ### `const fn` usage
//!
//! The [`UInt`] type provides a number of `const fn` inherent methods which
//! can be used for initializing and performing arithmetic on big integers in
//! const contexts:
//!
//! ```
//! use crypto_bigint::U256;
//!
//! // Parse a constant from a big endian hexadecimal string.
//! pub const MODULUS: U256 =
//!     U256::from_be_hex("ffffffff00000000ffffffffffffffffbce6faada7179e84f3b9cac2fc632551");
//!
//! // Compute `MODULUS` shifted right by 1 at compile time
//! pub const MODULUS_SHR1: U256 = MODULUS.shr_vartime(1);
//! ```
//!
//! ### Trait-based usage
//!
//! The [`UInt`] type itself does not implement the standard arithmetic traits
//! such as [`Add`], [`Sub`], [`Mul`], and [`Div`].
//!
//! To use these traits you must first pick a wrapper type which determines
//! overflow behavior: [`Wrapping`] or [`Checked`].
//!
//! #### Wrapping arithmetic
//!
//! ```
//! use crypto_bigint::{U256, Wrapping};
//!
//! let a = Wrapping(U256::MAX);
//! let b = Wrapping(U256::ONE);
//! let c = a + b;
//!
//! // `MAX` + 1 wraps back around to zero
//! assert_eq!(c.0, U256::ZERO);
//! ```
//!
//! #### Checked arithmetic
//!
//! ```
//! use crypto_bigint::{U256, Checked};
//!
//! let a = Checked::new(U256::ONE);
//! let b = Checked::new(U256::from(2u8));
//! let c = a + b;
//! assert_eq!(c.0.unwrap(), U256::from(3u8))
//! ```
//!
//! ### Modular arithmetic
//!
//! This library has initial support for modular arithmetic in the form of the
//! [`AddMod`], [`SubMod`], [`NegMod`], and [`MulMod`] traits, as well as the
//! support for the [`Rem`] trait when used with a [`NonZero`] operand.
//!
//! ```
//! use crypto_bigint::{AddMod, U256};
//!
//! // mod 3
//! let modulus = U256::from(3u8);
//!
//! // 1 + 1 mod 3 = 2
//! let a = U256::ONE.add_mod(&U256::ONE, &modulus);
//! assert_eq!(a, U256::from(2u8));
//!
//! // 2 + 1 mod 3 = 0
//! let b = a.add_mod(&U256::ONE, &modulus);
//! assert_eq!(b, U256::ZERO);
//! ```
//!
//! ### Random number generation
//!
//! When the `rand_core` or `rand` features of this crate are enabled, it's
//! possible to generate random numbers using any [`CryptoRng`] by using the
//! [`Random`] trait:
//!
//! ```
//! # #[cfg(feature = "rand")]
//! # {
//! use crypto_bigint::{Random, U256, rand_core::OsRng};
//!
//! let n = U256::random(&mut OsRng);
//! # }
//! ```
//!
//! #### Modular random number generation
//!
//! The [`RandomMod`] trait supports generating random numbers with a uniform
//! distribution around a given [`NonZero`] modulus.
//!
//! ```
//! # #[cfg(feature = "rand")]
//! # {
//! use crypto_bigint::{NonZero, RandomMod, U256, rand_core::OsRng};
//!
//! let modulus = NonZero::new(U256::from(3u8)).unwrap();
//! let n = U256::random_mod(&mut OsRng, &modulus);
//! # }
//! ```
//!
//! [`Add`]: core::ops::Add
//! [`Div`]: core::ops::Div
//! [`Mul`]: core::ops::Mul
//! [`Rem`]: core::ops::Rem
//! [`Sub`]: core::ops::Sub
//! [`CryptoRng`]: rand_core::CryptoRng

#![no_std]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![doc(
    html_logo_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg",
    html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg",
    html_root_url = "https://docs.rs/crypto-bigint/0.3.2"
)]
#![forbid(unsafe_code, clippy::unwrap_used)]
#![warn(
    missing_docs,
    missing_debug_implementations,
    missing_copy_implementations,
    rust_2018_idioms,
    trivial_casts,
    trivial_numeric_casts,
    unused_qualifications
)]

#[cfg(all(feature = "alloc", test))]
extern crate alloc;

#[macro_use]
mod macros;

#[cfg(feature = "generic-array")]
mod array;
mod checked;
mod limb;
mod non_zero;
mod traits;
mod uint;
mod wrapping;

pub use crate::{
    checked::Checked,
    limb::{Limb, LimbUInt, WideLimbUInt},
    non_zero::NonZero,
    traits::*,
    uint::*,
    wrapping::Wrapping,
};
pub use subtle;

pub(crate) use limb::{LimbInt, WideLimbInt};

#[cfg(feature = "generic-array")]
pub use {
    crate::array::{ArrayDecoding, ArrayEncoding, ByteArray},
    generic_array::{self, typenum::consts},
};

#[cfg(feature = "rand_core")]
pub use rand_core;

#[cfg(feature = "rlp")]
pub use rlp;

#[cfg(feature = "zeroize")]
pub use zeroize;

/// Import prelude for this crate: includes important traits.
pub mod prelude {
    pub use crate::traits::*;

    #[cfg(feature = "generic-array")]
    pub use crate::array::{ArrayDecoding, ArrayEncoding};
}