Class HybridKexExporter

java.lang.Object
zeroecho.sdk.hybrid.kex.HybridKexExporter
All Implemented Interfaces:
AutoCloseable, Destroyable
public final class HybridKexExporter extends Object implements Destroyable, AutoCloseable
Deterministic exporter for deriving multiple independent keys from a single hybrid KEX.

Many protocols require more than one key from a single handshake (for example, separate traffic keys for each direction, confirmation keys, or application exporters). This class provides a minimal key schedule API over HKDF-SHA256.

Construction

The exporter is seeded by a caller-supplied secret (typically the output of HybridKexContext.deriveSecret()). The exporter then derives sub-keys by varying HKDF info.

Security notes

  • Use distinct labels per purpose (for example "app/tx" vs "app/rx").
  • Bind transcript/context by including it in the info bytes.
Since:
1.0

  • Constructor Summary

    Constructors
    Constructor
    Description
    HybridKexExporter(byte[] rootSecret, byte[] salt)
    Creates an exporter seeded from a root secret.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    close()
    Closes this exporter by destroying its retained secret material.
    void
    destroy()
    Overwrites the exporter root secret and salt.
    byte[]
    export(String label, byte[] info, int outLenBytes)
    Derives outLenBytes bytes for a specific purpose.
    byte[]
    export(String label, int outLenBytes)
    Derives outLenBytes bytes for a specific purpose using only the label.
    boolean
    isDestroyed()
    Reports whether this exporter has been destroyed.

    Methods inherited from class Object

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

  • Constructor Details

    • HybridKexExporter

      public HybridKexExporter(byte[] rootSecret, byte[] salt)
      Creates an exporter seeded from a root secret.
      Parameters:
      rootSecret - root secret (must not be null)
      salt - optional HKDF salt (may be null)

  • Method Details

    • export

      public byte[] export(String label, byte[] info, int outLenBytes)
      Derives outLenBytes bytes for a specific purpose.
      Parameters:
      label - ASCII/UTF-8 label identifying the purpose (must not be null)
      info - optional additional binding info (may be null)
      outLenBytes - output length in bytes (1..8160)
      Returns:
      derived bytes
      Throws:
      IllegalArgumentException - if outLenBytes is out of range
      Since:
      1.0

    • export

      public byte[] export(String label, int outLenBytes)
      Derives outLenBytes bytes for a specific purpose using only the label.

      Equivalent to export(label, null, outLenBytes). Use the three-argument form to additionally bind a transcript or context value.

      Parameters:
      label - ASCII/UTF-8 label identifying the purpose (must not be null)
      outLenBytes - output length in bytes (1..8160)
      Returns:
      derived bytes
      Throws:
      IllegalArgumentException - if outLenBytes is out of range
      IllegalStateException - if the exporter has been destroyed
      Since:
      1.0

    • destroy

      public void destroy()
      Overwrites the exporter root secret and salt.

      Destruction is idempotent. All subsequent export or diagnostic access fails with IllegalStateException.

      Specified by:
      destroy in interface Destroyable

    • isDestroyed

      public boolean isDestroyed()
      Reports whether this exporter has been destroyed.
      Specified by:
      isDestroyed in interface Destroyable
      Returns:
      true after destruction

    • close

      public void close()
      Closes this exporter by destroying its retained secret material.
      Specified by:
      close in interface AutoCloseable