Table of Contents

Threefish256 Class

Definition

Namespace
Bodu.Security.Cryptography
Assembly
Bodu.Security.Cryptography.dll
Package
Bodu.Security.Cryptography 1.2.0
Source
Threefish.256.cs

Provides a managed implementation of the Threefish-256 tweakable symmetric block cipher, which operates on 256-bit (32-byte) blocks using a 256-bit key and a 128-bit tweak. This class cannot be inherited.

public sealed class Threefish256 : Threefish, IDisposable
Inheritance
Threefish256
Implements
Inherited Members
Extension Methods

Examples

using System.Security.Cryptography;
using Bodu.Security.Cryptography;
using Bodu.Security.Cryptography.Extensions;

using var tf = Threefish256.Create();
tf.Key = RandomNumberGenerator.GetBytes(32); // 256-bit key
tf.IV = RandomNumberGenerator.GetBytes(32); // matches the 256-bit block
tf.Tweak = RandomNumberGenerator.GetBytes(16); // 128-bit tweak
byte[] ciphertext = tf.Encrypt(plaintext);
byte[] roundTrip = tf.Decrypt(ciphertext);

Remarks

Threefish is the tweakable block cipher underlying the Skein hash function. This variant supports a variety of cipher block modes (CBC, CFB, OFB, CTR) via the BlockMode property, and is suitable for scenarios such as disk encryption or format-preserving encryption where a tweak is useful.

For other block sizes, see Threefish512 and Threefish1024.

Parameters at a glance.

  • Block size: 256 bits (32 bytes).
  • Key size: 256 bits (32 bytes).
  • Tweak size: 128 bits (16 bytes).
  • Default mode: CBC; default padding: PKCS7.

When to choose Threefish-256. Pick the 256-bit variant when you want a tweakable block cipher at a comparable security margin to AES-256 with a smaller block than the wider Threefish variants - useful for per-record encryption or short-tweak-driven schemes. Reach for Threefish512 when a wider block reduces birthday-bound exposure on long messages, or for Threefish1024 when the surrounding construction (e.g. a custom Skein-based AEAD) demands the widest block. For general-purpose encryption without a tweak requirement, prefer Aes.

Constructors

Threefish256()

Initializes a new instance of the Threefish256 class using a 256-bit block size, 256-bit key, and 128-bit tweak.

public Threefish256()

Methods

Create()

Creates a new Threefish256 instance with default parameters.

public static Threefish256 Create()

Returns

Threefish256

A new Threefish256 instance.

Remarks

The key, initialization vector, and tweak are generated on demand the first time they are accessed unless assigned explicitly via Key, IV, or Tweak.

CreateCipher(byte[], byte[])

Instantiates the concrete Threefish block cipher with the specified key and tweak.

protected override ThreefishBlockCipher CreateCipher(byte[] key, byte[] tweak)

Parameters

key byte[]

The encryption key.

tweak byte[]

The tweak value.

Returns

ThreefishBlockCipher

A configured IBlockCipher instance for encryption or decryption.

Exceptions

ArgumentNullException

Thrown when key is null.

CryptographicException

Thrown when the underlying cryptographic algorithm fails.

Applies to

ProductVersions
.NET8, 10

See Also

Using Threefish-256 (guide with full encrypt / decrypt examples)
Encryption basics
Cipher block modes
Padding
Threefish
Threefish512
Threefish1024
Threefish256Cipher
Skein256