Struct rand::chacha::ChaChaRng
[−]
[src]
pub struct ChaChaRng { buffer: [u32; STATE_WORDS], state: [u32; STATE_WORDS], index: usize, }
rand
): use rand
from crates.io
A random number generator that uses the ChaCha20 algorithm [1].
The ChaCha algorithm is widely accepted as suitable for
cryptographic purposes, but this implementation has not been
verified as such. Prefer a generator like OsRng
that defers to
the operating system for cases that need high security.
[1]: D. J. Bernstein, ChaCha, a variant of Salsa20
Fields
buffer | Unstable ( rand ): use |
state | Unstable ( rand ): use |
index | Unstable ( rand ): use |
Methods
impl ChaChaRng
fn new_unseeded() -> ChaChaRng
rand
): use rand
from crates.io
Create an ChaCha random number generator using the default fixed key of 8 zero words.
fn set_counter(&mut self, counter_low: u64, counter_high: u64)
rand
): use rand
from crates.io
Sets the internal 128-bit ChaCha counter to a user-provided value. This permits jumping arbitrarily ahead (or backwards) in the pseudorandom stream.
Since the nonce words are used to extend the counter to 128 bits,
users wishing to obtain the conventional ChaCha pseudorandom stream
associated with a particular nonce can call this function with
arguments 0, desired_nonce
.
fn init(&mut self, key: &[u32; KEY_WORDS])
rand
): use rand
from crates.io
Initializes self.state
with the appropriate key and constants
We deviate slightly from the ChaCha specification regarding the nonce, which is used to extend the counter to 128 bits. This is provably as strong as the original cipher, though, since any distinguishing attack on our variant also works against ChaCha with a chosen-nonce. See the XSalsa20 [1] security proof for a more involved example of this.
The modified word layout is:
text constant constant constant constant key key key key key key key key counter counter counter counter
[1]: Daniel J. Bernstein. Extending the Salsa20
nonce.
fn update(&mut self)
rand
): use rand
from crates.io
Refill the internal output buffer (self.buffer
)