xts implements the AES-XTS cipher mode as defined in the IEEE Std 1619-2007.

AES-XTS is an unauthenticated transparent encryption scheme designed for use cases like disk encryption. Transparent in the sense that the output size is the same as the input size, and that blocks can be written or read in an arbitrary order. Similarly to the ECB mode, XTS operates in blocks which are a multiple of the AES block size.

The security guarantees can be compared to the ECB ones, but with a different key for each block. That means following vulnerabilities exist:

• Traffic analysis: An observer can see when a certain block is written back to disk with a different value.
• Replay: An adversary may change a block back to an old value, if write access is available.
• Changing sectors: Changing of the cipher text will result in "random" plain text. Authentication or error detection can be done before encryption, to resist such attacks.

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.

// Undocumented types:
type block = struct {
	b1: aes::block,
	b2: aes::block,
	x: [aes::BLOCKSZ]u8,
};

fn decrypt(b: *block, dest: []u8, src: []u8, sector: u64) void;
fn encrypt(b: *block, dest: []u8, src: []u8, sector: u64) void;
fn finish(b: *block) void;
fn init(b: *block, key: []u8) void;
fn xts() block;

type block = struct {
	b1: aes::block,
	b2: aes::block,
	x: [aes::BLOCKSZ]u8,
};

fn decrypt(b: *block, dest: []u8, src: []u8, sector: u64) void;

fn encrypt(b: *block, dest: []u8, src: []u8, sector: u64) void;

fn finish(b: *block) void;

fn init(b: *block, key: []u8) void;

fn xts() block;