Package zeroecho.core.alg.elgamal

package zeroecho.core.alg.elgamal
ElGamal asymmetric encryption integration.

This package provides the ElGamal algorithm descriptor, a streaming cipher context, configuration specifications for padding and parameters, and encoded key specifications for import/export. Provider-specific details are kept behind small factories while roles and metadata remain explicit to higher layers.

Scope and responsibilities

  • Register ElGamal under a canonical identifier and declare KeyUsage.ENCRYPT and KeyUsage.DECRYPT roles.
  • Offer a streaming EncryptionContext that performs block-wise ElGamal transforms with selectable padding.
  • Expose specifications for padding modes and for explicit domain parameters, plus utility specs for encoded key import.
  • Encapsulate JCA/JCE interop and provider checks inside the algorithm descriptor and builders.

Components

  • ElgamalAlgorithm: algorithm descriptor that wires roles to the streaming cipher context and registers key builders for explicit parameter sets and encoded keys.
  • ElgamalCipherContext: streaming context that encrypts or decrypts data using ElGamal with block geometry derived from the modulus size and selected padding.
  • ElgamalEncSpec: immutable padding specification selecting either no padding or PKCS#1 v1.5-style padding.
  • ElgamalParamSpec: immutable wrapper for explicit domain parameters (modulus and generator), including a predefined RFC 7919 FFDHE2048 set.
  • ElgamalKeyGenSpec: parameters for generating fresh domain parameters and key pairs; typically disabled in favor of predefined parameter sets.
  • ElgamalPublicKeySpec / ElgamalPrivateKeySpec: encoded key specifications (X.509 and PKCS#8) with defensive copying and compact marshalling helpers; the private-key form is destroyable.

Design notes

  • Algorithm descriptors are immutable and thread-safe; cipher contexts are stateful and not thread-safe.
  • Padding choice affects plaintext-per-block and security properties; modern protocols should prefer KEM-based constructions for IND-CCA security.
  • Encoded key specs clone input and output arrays to avoid leaking internal state.
Since:
1.0