1 // Copyright 2018 Brian Smith.
2 //
3 // Permission to use, copy, modify, and/or distribute this software for any
4 // purpose with or without fee is hereby granted, provided that the above
5 // copyright notice and this permission notice appear in all copies.
6 //
7 // THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
8 // WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 // MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
10 // SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 // WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14 
15 use crate::error;
16 
17 /// A nonce for a single AEAD opening or sealing operation.
18 ///
19 /// The user must ensure, for a particular key, that each nonce is unique.
20 ///
21 /// `Nonce` intentionally doesn't implement `Clone` to ensure that each one is
22 /// consumed at most once.
23 pub struct Nonce([u8; NONCE_LEN]);
24 
25 impl Nonce {
26     /// Constructs a `Nonce` with the given value, assuming that the value is
27     /// unique for the lifetime of the key it is being used with.
28     ///
29     /// Fails if `value` isn't `NONCE_LEN` bytes long.
30     #[inline]
try_assume_unique_for_key(value: &[u8]) -> Result<Self, error::Unspecified>31     pub fn try_assume_unique_for_key(value: &[u8]) -> Result<Self, error::Unspecified> {
32         let value: &[u8; NONCE_LEN] = value.try_into()?;
33         Ok(Self::assume_unique_for_key(*value))
34     }
35 
36     /// Constructs a `Nonce` with the given value, assuming that the value is
37     /// unique for the lifetime of the key it is being used with.
38     #[inline]
assume_unique_for_key(value: [u8; NONCE_LEN]) -> Self39     pub fn assume_unique_for_key(value: [u8; NONCE_LEN]) -> Self {
40         Self(value)
41     }
42 }
43 
44 impl AsRef<[u8; NONCE_LEN]> for Nonce {
as_ref(&self) -> &[u8; NONCE_LEN]45     fn as_ref(&self) -> &[u8; NONCE_LEN] {
46         &self.0
47     }
48 }
49 
50 /// All the AEADs we support use 96-bit nonces.
51 pub const NONCE_LEN: usize = 96 / 8;
52