Class AsconAead128

Namespace

CryptoHives.Foundation.Security.Cryptography.Cipher

Assembly

CryptoHives.Foundation.Security.Cryptography.dll

Ascon-AEAD128 authenticated encryption as specified in NIST SP 800-232.

public sealed class AsconAead128 : IAeadCipher, IDisposable

Inheritance

object

AsconAead128

Implements

IAeadCipher

IDisposable

Inherited Members

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

object.GetType()

Remarks

Ascon-AEAD128 is the primary AEAD algorithm from the NIST Lightweight Cryptography standard (SP 800-232). It provides authenticated encryption with associated data using a 128-bit key, 128-bit nonce, and 128-bit authentication tag.

Ascon was the winner of the NIST Lightweight Cryptography competition (2023), designed for constrained environments while maintaining strong security guarantees.

Security properties:

• 128-bit security level
• 128-bit authentication tag
• Sponge-based construction with 320-bit state
• Resistant to timing attacks (no table lookups)

Important: Never reuse a (key, nonce) pair. Each encryption must use a unique 128-bit (16-byte) nonce.

Example usage:

using var aead = AsconAead128.Create(key);
// Encrypt with associated data
byte[] ciphertext = aead.Encrypt(nonce, plaintext, associatedData);
// Decrypt and verify
byte[] plaintext = aead.Decrypt(nonce, ciphertext, associatedData);

References:

• NIST SP 800-232
• Reference Implementation
• Ascon Homepage

Constructors

AsconAead128(byte[])

Initializes a new instance of the AsconAead128 class.

public AsconAead128(byte[] key)

Parameters

key byte[]

The 16-byte key.

Exceptions

ArgumentNullException

key is null.

ArgumentException

key is not 16 bytes.

Fields

KeySizeBytesConst

Key size in bytes (128 bits).

public const int KeySizeBytesConst = 16

Field Value

int

NonceSizeBytesConst

Nonce size in bytes (128 bits).

public const int NonceSizeBytesConst = 16

Field Value

int

TagSizeBytesConst

Tag size in bytes (128 bits).

public const int TagSizeBytesConst = 16

Field Value

int

Properties

AlgorithmName

Gets the algorithm name.

public string AlgorithmName { get; }

Property Value

string

KeySizeBytes

Gets the key size in bytes.

public int KeySizeBytes { get; }

Property Value

int

NonceSizeBytes

Gets the nonce size in bytes.

public int NonceSizeBytes { get; }

Property Value

int

TagSizeBytes

Gets the authentication tag size in bytes.

public int TagSizeBytes { get; }

Property Value

int

Methods

Create(byte[])

Creates a new Ascon-AEAD128 instance.

public static AsconAead128 Create(byte[] key)

Parameters

key byte[]

The 16-byte key.

Returns

AsconAead128

A new Ascon-AEAD128 instance.

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

Decrypts the ciphertext (with appended tag) and verifies authenticity.

public byte[] Decrypt(ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> ciphertextWithTag, ReadOnlySpan<byte> associatedData = default)

Parameters

nonce ReadOnlySpan<byte>

The nonce used during encryption.

ciphertextWithTag ReadOnlySpan<byte>

The ciphertext with appended authentication tag.

associatedData ReadOnlySpan<byte>

Additional authenticated data (must match encryption).

Returns

byte[]

The decrypted plaintext.

Exceptions

CryptographicException

Authentication failed - the data has been tampered with or the wrong key/nonce was used.

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

Decrypts the ciphertext and verifies the authentication tag.

public bool Decrypt(ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> ciphertext, ReadOnlySpan<byte> tag, Span<byte> plaintext, ReadOnlySpan<byte> associatedData = default)

Parameters

nonce ReadOnlySpan<byte>

The nonce used during encryption.

ciphertext ReadOnlySpan<byte>

The encrypted data.

tag ReadOnlySpan<byte>

The authentication tag to verify.

plaintext Span<byte>

The output buffer for decrypted data (same size as ciphertext).

associatedData ReadOnlySpan<byte>

Additional authenticated data (must match encryption).

Returns

bool

True if decryption and authentication succeeded; false if authentication failed.

Exceptions

ArgumentException

nonce or tag is not the correct size, or plaintext buffer is too small.

Dispose()

Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.

public void Dispose()

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

Encrypts the plaintext and returns ciphertext with appended tag.

public byte[] Encrypt(ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> plaintext, ReadOnlySpan<byte> associatedData = default)

Parameters

nonce ReadOnlySpan<byte>

The unique nonce for this encryption.

plaintext ReadOnlySpan<byte>

The data to encrypt.

associatedData ReadOnlySpan<byte>

Additional data to authenticate (optional).

Returns

byte[]

The ciphertext with authentication tag appended.

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

Encrypts the plaintext and computes the authentication tag.

public void Encrypt(ReadOnlySpan<byte> nonce, ReadOnlySpan<byte> plaintext, Span<byte> ciphertext, Span<byte> tag, ReadOnlySpan<byte> associatedData = default)

Parameters

nonce ReadOnlySpan<byte>

The unique nonce for this encryption.

plaintext ReadOnlySpan<byte>

The data to encrypt.

ciphertext Span<byte>

The output buffer for ciphertext (same size as plaintext).

tag Span<byte>

The output buffer for the authentication tag.

associatedData ReadOnlySpan<byte>

Additional data to authenticate (optional).

Exceptions

ArgumentException

nonce is not the correct size, or ciphertext or tag buffers are too small.