Struct ChunkCipher 

pub struct ChunkCipher { /* private fields */ }

ChunkCipher wraps the ChaCha20-Poly1305 key used to encrypt and decrypt chunk data before/after RLNC coding.

Production path: create via ChunkCipher::for_user which derives a CEK from the owner’s identity secret and the plaintext chunk hash.

Implementations

impl ChunkCipher

pub fn for_user(secret_material: &[u8; 32], plaintext_hash: &[u8; 32]) -> Self

Derive the Content Encryption Key for a chunk and build a cipher.

secret_material comes from crate::identity::Identity::secret_material. plaintext_hash is BLAKE3(chunk_data) computed before encryption.

cek = BLAKE3_keyed(secret_material, "billpouch/cek/v1" || plaintext_hash)

pub fn from_raw_key(key: [u8; 32]) -> Self

Build a cipher from a raw 32-byte key.

Useful for tests and for future key-wrapping schemes.

pub fn encrypt(&self, plaintext: &[u8]) -> BpResult<Vec<u8>>

Encrypt plaintext and return nonce(12) || ciphertext_with_tag(len+16).

A fresh random nonce is generated for every call, guaranteeing that repeated encryptions of the same plaintext produce different outputs.

pub fn decrypt(&self, blob: &[u8]) -> BpResult<Vec<u8>>

Decrypt a blob produced by encrypt.

Returns the original plaintext or an error if the tag verification fails (wrong key, wrong network, or corrupted data).