Struct rand_hc::Hc128Rng

pub struct Hc128Rng(/* private fields */);

A cryptographically secure random number generator that uses the HC-128 algorithm.

HC-128 is a stream cipher designed by Hongjun Wu¹, that we use as an RNG. It is selected as one of the “stream ciphers suitable for widespread adoption” by eSTREAM².

HC-128 is an array based RNG. In this it is similar to RC-4 and ISAAC before it, but those have never been proven cryptographically secure (or have even been significantly compromised, as in the case of RC-4³).

Because HC-128 works with simple indexing into a large array and with a few operations that parallelize well, it has very good performance. The size of the array it needs, 4kb, can however be a disadvantage.

This implementation is not based on the version of HC-128 submitted to the eSTREAM contest, but on a later version by the author with a few small improvements from December 15, 2009⁴.

HC-128 has no known weaknesses that are easier to exploit than doing a brute-force search of 2¹²⁸. A very comprehensive analysis of the current state of known attacks / weaknesses of HC-128 is given in Some Results On Analysis And Implementation Of HC-128 Stream Cipher⁵.

The average cycle length is expected to be 2^1024*32+10-1 = 2³²⁷⁷⁷. We support seeding with a 256-bit array, which matches the 128-bit key concatenated with a 128-bit IV from the stream cipher.

This implementation uses an output buffer of sixteen u32 words, and uses BlockRng to implement the RngCore methods.

References

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1. Hongjun Wu (2008). “The Stream Cipher HC-128”. The eSTREAM Finalists, LNCS 4986, pp. 39–47, Springer-Verlag. ↩

2. eSTREAM: the ECRYPT Stream Cipher Project ↩

3. Internet Engineering Task Force (February 2015), “Prohibiting RC4 Cipher Suites”. ↩

4. Hongjun Wu, Stream Ciphers HC-128 and HC-256 ↩

5. Shashwat Raizada (January 2015),“Some Results On Analysis And Implementation Of HC-128 Stream Cipher”. ↩

Trait Implementations

impl Clone for Hc128Rng

fn clone(&self) -> Hc128Rng

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Hc128Rng

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl RngCore for Hc128Rng

fn next_u32(&mut self) -> u32

Return the next random u32.

fn next_u64(&mut self) -> u64

Return the next random u64.

fn fill_bytes(&mut self, dest: &mut [u8])

Fill dest with random data.

fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>

Fill dest entirely with random data.

impl SeedableRng for Hc128Rng

type Seed = <Hc128Core as SeedableRng>::Seed

Seed type, which is restricted to types mutably-dereferencable as u8 arrays (we recommend [u8; N] for some N).

fn from_seed(seed: Self::Seed) -> Self

Create a new PRNG using the given seed.

fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error>

Create a new PRNG seeded from another Rng.

fn seed_from_u64(state: u64) -> Self

Create a new PRNG using a u64 seed.

impl CryptoRng for Hc128Rng