crypto::chacha provides an implementation of the Chacha20 and XChacha20 stream ciphers.

Use chacha20 to create a crypto::cipher::xorstream and either chacha20_init or xchacha20_init to set the handle, key and nonce of the appropriate size, NONCESZ for chacha20 or XNONCESZ for XChacha20. After calling the appropriate init function, io::write may be used to encrypt blocks to the handle or io::read to decrypt blocks from the handle. The stream must be closed with io::close to wipe sensitive data from memory.

Writing blocks of length BLOCKSZ is not required. However, seeking the key stream with setctr only operates in units of BLOCKSZ.

This is a low-level module which implements cryptographic primitives. Direct use of cryptographic primitives is not recommended for non-experts, as incorrect use of these primitives can easily lead to the introduction of security vulnerabilities. Non-experts are advised to use the high-level operations available in the top-level crypto:: module.

Be advised that Hare's cryptography implementations have not been audited.

type stream = struct {
	cipher::xorstream,
	state: [16]u32,
	xorbuf: [BLOCKSZ]u8,
	xorused: size,
	rounds: size,
};

def BLOCKSZ: size = 64;
def KEYSZ: size = 32;
def NONCESZ: size = 12;
def XNONCESZ: size = 24;

fn chacha20() stream;
fn chacha20_init(s: *stream, h: io::handle, key: []u8, nonce: []u8) void;
fn hchacha20(out: []u8, key: []u8, nonce: []u8) void;
fn setctr(s: *stream, counter: u32) void;
fn xchacha20_init(s: *stream, h: io::handle, key: []u8, nonce: []u8) void;

type stream = struct {
	cipher::xorstream,
	state: [16]u32,
	xorbuf: [BLOCKSZ]u8,
	xorused: size,
	rounds: size,
};

def BLOCKSZ: size = 64;

def KEYSZ: size = 32;

def NONCESZ: size = 12;

def XNONCESZ: size = 24;

fn chacha20() stream;

fn chacha20_init(s: *stream, h: io::handle, key: []u8, nonce: []u8) void;

fn hchacha20(out: []u8, key: []u8, nonce: []u8) void;

fn setctr(s: *stream, counter: u32) void;

fn xchacha20_init(s: *stream, h: io::handle, key: []u8, nonce: []u8) void;