Table of Contents

Threefish1024Cipher Class

Definition

Namespace
Bodu.Security.Cryptography
Assembly
Bodu.Security.Cryptography.dll
Package
Bodu.Security.Cryptography 1.2.0
Source
ThreefishBlockCipher.1024.Avx512.cs

AVX-512 vectorised implementation of Threefish1024Cipher. The sixteen 64-bit state words are split across two Vector512<T> registers - loVec holds the eight even-position words (x0, x2, x4, x6, x8, x10, x12, x14) and hiVec the eight odd-position words (x1, x3, x5, x7, x9, x11, x13, x15). Each round performs a vector add, a per-lane variable rotate ( VPROLVQ), an XOR, and a pair of single-source VPERMQ shuffles that realign the registers for the next round's MIX pairing.

public sealed class Threefish1024Cipher : ThreefishBlockCipher, IBlockCipher, IDisposable
Inheritance
Threefish1024Cipher
Implements
Inherited Members
Extension Methods

Examples

// Direct single-block use - most callers should prefer the Threefish1024 SymmetricAlgorithm.
byte[] key   = new byte[128];   // 1024-bit key
byte[] tweak = new byte[16];    // 128-bit tweak
RandomNumberGenerator.Fill(key);
RandomNumberGenerator.Fill(tweak);

using var cipher = new Threefish1024Cipher(key, tweak);

byte[] plaintext  = new byte[128];   // one 1024-bit block
byte[] ciphertext = new byte[128];
cipher.Encrypt(plaintext, ciphertext);

byte[] roundtrip = new byte[128];
cipher.Decrypt(ciphertext, roundtrip);
// roundtrip equals plaintext

Remarks

The per-round word permutation has a uniform 4-round cycle: the same two lane-shuffle vectors realign both registers for every inter-round transition within a group, and after four shuffles both registers return to canonical layout - exactly where the subkey injection lands.

Gated on IsSupported directly because the implementation operates on Vector512<T> rather than Vector256<T>, so the Vector Length extensions are not required.

Constructors

Threefish1024Cipher(ReadOnlySpan<byte>, ReadOnlySpan<byte>)

Initializes a new instance of the Threefish1024Cipher class using the specified key and tweak.

public Threefish1024Cipher(ReadOnlySpan<byte> key, ReadOnlySpan<byte> tweak)

Parameters

key ReadOnlySpan<byte>

The 1024-bit (128-byte) key used for encryption and decryption.

tweak ReadOnlySpan<byte>

The 128-bit (16-byte) tweak value used to modify the block cipher behavior.

Fields

KeySize

Length of the Threefish-1024 key is 1024 bits (128 bytes).

public const int KeySize = 1024

Field Value

int

Properties

BlockSize

Gets the block size, in bits, of the cipher (for example, 128 bits / 16 bytes for AES).

public override int BlockSize { get; }

Property Value

int

The block size, in bits.

Remarks

The block size is expressed in bits to align with the BCL convention used by BlockSize. Byte-array operations (encrypt, decrypt, slice) convert to bytes at the call site as BlockSize / 8.

BlockWords

Gets the number of 64-bit words in a single block.

protected override int BlockWords { get; }

Property Value

int

RotationSchedule

Gets the rotation constants used for MIX/UNMIX operations in this cipher variant.

protected override int[] RotationSchedule { get; }

Property Value

int[]

Rounds

Gets the total number of cipher rounds.

protected override int Rounds { get; }

Property Value

int

Methods

Decrypt(ReadOnlySpan<byte>, Span<byte>)

Decrypts a single 128-byte ciphertext block using the Threefish-1024 cipher and writes the result to the specified output buffer.

public override void Decrypt(ReadOnlySpan<byte> input, Span<byte> output)

Parameters

input ReadOnlySpan<byte>

The 128-byte ciphertext block to decrypt.

output Span<byte>

The 128-byte buffer to receive the decrypted plaintext block.

Remarks

Dispatches to an AVX-512F vectorised implementation when supported by the host, falling back to a scalar register-resident implementation otherwise. Dispatch is gated by Bodu.Security.Cryptography.SimdCapabilities.Avx512F, which combines the hardware intrinsic with the process-wide SIMD opt-out; on hosts without AVX-512 it still folds to a compile-time constant that removes the branch, otherwise it reduces to a single cached-boolean load.

Exceptions

ObjectDisposedException

Thrown if the cipher has been disposed.

ArgumentException

Thrown if input or output is not 128 bytes.

Encrypt(ReadOnlySpan<byte>, Span<byte>)

Encrypts a single 128-byte plaintext block using the Threefish-1024 cipher and writes the result to the specified output buffer.

public override void Encrypt(ReadOnlySpan<byte> input, Span<byte> output)

Parameters

input ReadOnlySpan<byte>

The 128-byte plaintext block to encrypt.

output Span<byte>

The 128-byte buffer to receive the encrypted ciphertext block.

Remarks

Dispatches to an AVX-512F vectorised implementation when supported by the host, falling back to a scalar register-resident implementation otherwise. Dispatch is gated by Bodu.Security.Cryptography.SimdCapabilities.Avx512F, which combines the hardware intrinsic with the process-wide SIMD opt-out; on hosts without AVX-512 it still folds to a compile-time constant that removes the branch, otherwise it reduces to a single cached-boolean load.

Exceptions

ObjectDisposedException

Thrown if the cipher has been disposed.

ArgumentException

Thrown if input or output is not 128 bytes.

Applies to

ProductVersions
.NET8, 10

See Also

Composing primitives - direct use vs. SymmetricAlgorithm
Threefish1024