Package org.bouncycastle.pqc.crypto.ntru

## Class NTRUEngine

- java.lang.Object
- - org.bouncycastle.pqc.crypto.ntru.NTRUEngine

- All Implemented Interfaces:
    `AsymmetricBlockCipher`

      public class NTRUEngine
      extends java.lang.Object
      implements AsymmetricBlockCipher

  Encrypts, decrypts data and generates key pairs.
  The parameter p is hardcoded to 3.

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `NTRUEngine()` | Constructs a new instance with a set of encryption parameters.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `protected IntegerPolynomial` | `decrypt​(IntegerPolynomial e, Polynomial priv_t, IntegerPolynomial priv_fp)` |
    `protected IntegerPolynomial` | `encrypt​(IntegerPolynomial m, TernaryPolynomial r, IntegerPolynomial pubKey)` |
    `int` | `getInputBlockSize()` | returns the largest size an input block can be.
    `int` | `getOutputBlockSize()` | returns the maximum size of the block produced by this cipher.
    `void` | `init​(boolean forEncryption, CipherParameters parameters)` | initialise the cipher.
    `byte[]` | `processBlock​(byte[] in, int inOff, int len)` | process the block of len bytes stored in in from offset inOff.

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### NTRUEngine

          public NTRUEngine()

      Constructs a new instance with a set of encryption parameters.

  - ### Method Detail

    - #### init

          public void init​(boolean forEncryption,
                           CipherParameters parameters)

      Description copied from interface: `AsymmetricBlockCipher`
      initialise the cipher.
      Specified by:
        `init` in interface `AsymmetricBlockCipher`
      Parameters:
        `forEncryption` - if true the cipher is initialised for encryption, if false for decryption.
        `parameters` - the key and other data required by the cipher.

    - #### getInputBlockSize

          public int getInputBlockSize()

      Description copied from interface: `AsymmetricBlockCipher`
      returns the largest size an input block can be.
      Specified by:
        `getInputBlockSize` in interface `AsymmetricBlockCipher`
      Returns:
        maximum size for an input block.

    - #### getOutputBlockSize

          public int getOutputBlockSize()

      Description copied from interface: `AsymmetricBlockCipher`
      returns the maximum size of the block produced by this cipher.
      Specified by:
        `getOutputBlockSize` in interface `AsymmetricBlockCipher`
      Returns:
        maximum size of the output block produced by the cipher.

    - #### processBlock

          public byte[] processBlock​(byte[] in,
                                     int inOff,
                                     int len)
                              throws InvalidCipherTextException

      Description copied from interface: `AsymmetricBlockCipher`
      process the block of len bytes stored in in from offset inOff.
      Specified by:
        `processBlock` in interface `AsymmetricBlockCipher`
      Parameters:
        `in` - the input data
        `inOff` - offset into the in array where the data starts
        `len` - the length of the block to be processed.
      Returns:
        the resulting byte array of the encryption/decryption process.
      Throws:
        `InvalidCipherTextException` - data decrypts improperly.

    - #### encrypt

          protected IntegerPolynomial encrypt​(IntegerPolynomial m,
                                              TernaryPolynomial r,
                                              IntegerPolynomial pubKey)

    - #### decrypt

          protected IntegerPolynomial decrypt​(IntegerPolynomial e,
                                              Polynomial priv_t,
                                              IntegerPolynomial priv_fp)

      Parameters:
        `e` -
        `priv_t` - a polynomial such that if `fastFp=true`, `f=1+3*priv_t`; otherwise, `f=priv_t`
        `priv_fp` -
      Returns:
        an IntegerPolynomial representing the output.