Class ChaChaHeaderCodec

java.lang.Object

zeroecho.core.alg.chacha.ChaChaHeaderCodec

All Implemented Interfaces:

SymmetricHeaderCodec

public final class ChaChaHeaderCodec
extends Object
implements SymmetricHeaderCodec

ChaCha20 streaming header codec

Implements SymmetricHeaderCodec for the ChaCha20 stream cipher. Encodes a compact header containing:

• a 12-byte nonce (IV), and
• the stream counter as a 7-bit packed integer.

The nonce and counter are exchanged through the bound CtxInterface using ConfluxKeys.iv(String) and ConfluxKeys.tagBits(String) keys, namespaced by the algorithm id (e.g., "CHACHA20").

Header layout

 [0..11]   : 12-byte nonce (IV)
 [12..N]   : counter encoded via 7-bit packed integer

Behavior

• writeHeader: requires iv(id) in context (12 bytes). Writes the nonce, then the counter from tagBits(id) if present, otherwise uses 1.
• readHeader: reads nonce and counter and stores them into the context under the same keys.

Since:

1.0

Constructor Summary

Constructors

Constructor	Description
ChaChaHeaderCodec()	Creates a stateless ChaCha20 stream-header codec.

Method Summary

Modifier and Type	Method	Description
InputStream	readHeader(InputStream in, CryptoAlgorithm algorithm, CtxInterface ctx)	Reads a ChaCha20 header from the input and hydrates the context.
void	writeHeader(OutputStream out, CryptoAlgorithm algorithm, CtxInterface ctx)	Writes the ChaCha20 header to the provided output.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ChaChaHeaderCodec

public ChaChaHeaderCodec()

Creates a stateless ChaCha20 stream-header codec.

Method Details

writeHeader

public void writeHeader(OutputStream out,
 CryptoAlgorithm algorithm,
 CtxInterface ctx)
                 throws IOException

Writes the ChaCha20 header to the provided output.

Reads a 12-byte nonce from ConfluxKeys.iv(String) and a stream counter from ConfluxKeys.tagBits(String) (defaulting to 1 if absent). Emits the nonce followed by the counter encoded as a 7-bit packed integer, then flushes.

Specified by:

writeHeader in interface SymmetricHeaderCodec

Parameters:

out - destination stream

algorithm - algorithm instance used for context key scoping

ctx - operation context carrying nonce and optional counter

Throws:

IOException - if the nonce is missing/invalid or I/O fails

readHeader

public InputStream readHeader(InputStream in,
 CryptoAlgorithm algorithm,
 CtxInterface ctx)
                       throws IOException

Reads a ChaCha20 header from the input and hydrates the context.

Consumes a 12-byte nonce and a 7-bit packed counter, then stores them into ctx under ConfluxKeys.iv(String) and ConfluxKeys.tagBits(String), respectively. Returns the same input stream positioned after the header.

Specified by:

readHeader in interface SymmetricHeaderCodec

Parameters:

in - source stream

algorithm - algorithm instance used for context key scoping

ctx - context to populate with nonce and counter

Returns:

the input stream positioned after the header

Throws:

IOException - if the header is malformed or I/O fails