Module hctr2 

HCTR2 (Hash-CTR-Hash) length-preserving wide-block tweakable cipher.

HCTR2 provides full-block diffusion: any change to plaintext affects the entire ciphertext. It requires no nonce or authentication tag, making it suitable for constrained environments.

Construction uses:

• Single encryption key
• Polyval universal hash function
• XCTR mode for wide-block encryption (counter-based)

Security properties:

• Ciphertext length equals plaintext length (no expansion)
• Requires unique (key, tweak) pairs for security
• No authentication - consider AEAD if integrity protection is needed
• Minimum message length: 16 bytes (one AES block)

Structs

Hctr2

Generic HCTR2 cipher parameterized by AES key size.

Traits

AesCipher

Trait for AES ciphers used in HCTR2.

Type Aliases

Hctr2ErrorDeprecated

Hctr2_128

HCTR2 with AES-128 encryption.

Hctr2_256

HCTR2 with AES-256 encryption.