chiapos-chacha8

This is a byte-for-byte compatible implementation of chiapos' ChaCha8 in Rust. It has been manually verified in a custom implementation of chiapos in Rust to produce identical output.

On top of producing identical output, this implementation is also multi-threaded using Rayon producing data extremely fast.

Usage

This crate has some strict expectations that match the original use-case:

• Output data must be in 512bit blocks
• The input key must be 256 bits long (ChaCha8 takes either a 128bit or 256bit input in the original implementation)
• The IV will be zeroed

```rust // Randomize this key however you would like let mut key = [0u8; 32]; let chacha8 = ChaCha8::newfrom256bit_key(&key);

// Output data goes in this vec, note that 64 * 8 = 512bits let numblocks = 128; let mut chachablocks = vec![0u8; 64 * num_blocks];

// pos is the offset in the output keystream let pos = 0; chacha8.getkeystream(pos, &mut chachablocks); ```

Benefits

This crate generates pseudorandom data extremely fast in 512bit blocks. The output is also deterministic for the same inputs.

Caveats

This crate makes no guarantees about:

• Correctness with regards to the original ChaCha8 implementation / specification
• Cryptographical security