https://github.com/pheki/xts-mode

XTS block mode implementation in rust
https://github.com/pheki/xts-mode

cryptography hacktoberfest rust xts

Last synced: about 22 hours ago
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XTS block mode implementation in rust

• Host: GitHub
• URL: https://github.com/pheki/xts-mode
• Owner: pheki
• License: mit
• Created: 2020-04-30T05:57:17.000Z (over 4 years ago)
• Default Branch: main
• Last Pushed: 2024-07-26T03:43:14.000Z (4 months ago)
• Last Synced: 2024-11-07T21:46:39.898Z (8 days ago)
• Topics: cryptography, hacktoberfest, rust, xts
• Language: Rust
• Homepage:
• Size: 175 KB
• Stars: 11
• Watchers: 2
• Forks: 4
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

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README

        
# xts-mode

[XTS block mode](https://en.wikipedia.org/wiki/Disk_encryption_theory#XEX-based_tweaked-codebook_mode_with_ciphertext_stealing_(XTS)) implementation in Rust.

Currently this implementation supports only ciphers with 128-bit (16-byte) block size (distinct from key size). Note that AES-256 uses 128-bit blocks, so it works with this crate. If you require other cipher block sizes, please open an issue.

## Examples:

Encrypting and decrypting multiple sectors at a time:

```rust

use aes::{Aes128, cipher::KeyInit, cipher::generic_array::GenericArray};

use xts_mode::{Xts128, get_tweak_default};

// Load the encryption key

let key = [1; 32];

let plaintext = [5; 0x400];

// Load the data to be encrypted

let mut buffer = plaintext.to_owned();

let cipher_1 = Aes128::new(GenericArray::from_slice(&key[..16]));

let cipher_2 = Aes128::new(GenericArray::from_slice(&key[16..]));

let xts = Xts128::::new(cipher_1, cipher_2);

let sector_size = 0x200;

let first_sector_index = 0;

// Encrypt data in the buffer

xts.encrypt_area(&mut buffer, sector_size, first_sector_index, get_tweak_default);

// Decrypt data in the buffer

xts.decrypt_area(&mut buffer, sector_size, first_sector_index, get_tweak_default);

assert_eq!(&buffer[..], &plaintext[..]);

```

AES-256 works too:

```rust

use aes::{Aes256, cipher::KeyInit, cipher::generic_array::GenericArray};

use xts_mode::{Xts128, get_tweak_default};

// Load the encryption key

let key = [1; 64];

let plaintext = [5; 0x400];

// Load the data to be encrypted

let mut buffer = plaintext.to_owned();

let cipher_1 = Aes256::new(GenericArray::from_slice(&key[..32]));

let cipher_2 = Aes256::new(GenericArray::from_slice(&key[32..]));

let xts = Xts128::::new(cipher_1, cipher_2);

let sector_size = 0x200;

let first_sector_index = 0;

xts.encrypt_area(&mut buffer, sector_size, first_sector_index, get_tweak_default);

xts.decrypt_area(&mut buffer, sector_size, first_sector_index, get_tweak_default);

assert_eq!(&buffer[..], &plaintext[..]);

```

Encrypting and decrypting a single sector:

```rust

use aes::{Aes128, cipher::KeyInit, cipher::generic_array::GenericArray};

use xts_mode::{Xts128, get_tweak_default};

// Load the encryption key

let key = [1; 32];

let plaintext = [5; 0x200];

// Load the data to be encrypted

let mut buffer = plaintext.to_owned();

let cipher_1 = Aes128::new(GenericArray::from_slice(&key[..16]));

let cipher_2 = Aes128::new(GenericArray::from_slice(&key[16..]));

let xts = Xts128::::new(cipher_1, cipher_2);

let tweak = get_tweak_default(0); // 0 is the sector index

// Encrypt data in the buffer

xts.encrypt_sector(&mut buffer, tweak);

// Decrypt data in the buffer

xts.decrypt_sector(&mut buffer, tweak);

assert_eq!(&buffer[..], &plaintext[..]);

```

Decrypting a [NCA](https://switchbrew.org/wiki/NCA_Format) (nintendo content archive) header:

```rust

use aes::{Aes128, cipher::KeyInit, cipher::generic_array::GenericArray};

use xts_mode::{Xts128, get_tweak_default};

pub fn get_nintendo_tweak(sector_index: u128) -> [u8; 0x10] {

    sector_index.to_be_bytes()

}

// Load the header key

let header_key = &[0; 0x20];

// Read into buffer header to be decrypted

let mut buffer = vec![0; 0xC00];

let cipher_1 = Aes128::new(GenericArray::from_slice(&header_key[..0x10]));

let cipher_2 = Aes128::new(GenericArray::from_slice(&header_key[0x10..]));

let mut xts = Xts128::new(cipher_1, cipher_2);

// Decrypt the first 0x400 bytes of the header in 0x200 sections

xts.decrypt_area(&mut buffer[0..0x400], 0x200, 0, get_nintendo_tweak);

let magic = &buffer[0x200..0x204];

assert_eq!(magic, b"NCA3"); // In older NCA versions the section index used in header encryption was different

// Decrypt the rest of the header

xts.decrypt_area(&mut buffer[0x400..0xC00], 0x200, 2, get_nintendo_tweak);

```