ISAPEngine (Bouncy Castle Library 1.85 API Specification)
Date: 2026-07-12

org.bouncycastle.crypto.engines

## Class ISAPEngine

- java.lang.Object
- - org.bouncycastle.crypto.engines.ISAPEngine

- All Implemented Interfaces:
    AEADCipher

      public class ISAPEngine
      extends java.lang.Object

  ISAP AEAD v2, https://isap.iaik.tugraz.at/ https://csrc.nist.gov/CSRC/media/Projects/lightweight-cryptography/documents/finalist-round/updated-spec-doc/isap-spec-final.pdf

  ISAP AEAD v2 with reference to C Reference Impl from: https://github.com/isap-lwc/isap-code-package

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `protected static interface` | `AEADBaseEngine.AADOperator`
    `protected static class` | `AEADBaseEngine.AADOperatorType`
    `protected static class` | `AEADBaseEngine.DataLimitCounter`
    `protected static interface` | `AEADBaseEngine.DataOperator`
    `protected static class` | `AEADBaseEngine.DataOperatorType`
    `protected static class` | `AEADBaseEngine.DecryptionFailureCounter`
    `protected static class` | `AEADBaseEngine.ErasableOutputStream`
    `protected static class` | `AEADBaseEngine.ProcessingBufferType`
    `protected static class` | `AEADBaseEngine.State`
    `protected static class` | `AEADBaseEngine.StreamAADOperator`
    `static class` | `ISAPEngine.IsapType`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected int` | `AADBufferSize`
    `protected AEADBaseEngine.AADOperator` | `aadOperator`
    `protected java.lang.String` | `algorithmName`
    `protected int` | `BlockSize`
    `protected AEADBaseEngine.DataLimitCounter` | `dataLimitCounter`
    `protected AEADBaseEngine.DataOperator` | `dataOperator`
    `protected AEADBaseEngine.DecryptionFailureCounter` | `decryptionFailureCounter`
    `protected boolean` | `forEncryption`
    `protected byte[]` | `initialAssociatedText`
    `protected int` | `IV_SIZE`
    `protected int` | `KEY_SIZE`
    `protected byte[]` | `m_aad`
    `protected int` | `m_aadPos`
    `protected byte[]` | `m_buf`
    `protected int` | `m_bufferSizeDecrypt`
    `protected int` | `m_bufPos`
    `protected AEADBaseEngine.State` | `m_state`
    `protected byte[]` | `mac`
    `protected int` | `MAC_SIZE`
    `protected int` | `macSizeLowerBound`
    `protected org.bouncycastle.crypto.engines.AEADBaseEngine.AADProcessingBuffer` | `processor`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `ISAPEngine(ISAPEngine.IsapType isapType)`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `checkAAD()`
    `protected boolean` | `checkData(boolean isDoFinal)`
    `int` | `doFinal(byte[] output, int outOff)` Finish the operation either appending or verifying the MAC at the end of the data.
    `protected void` | `ensureInitialized()`
    `protected void` | `ensureSufficientInputBuffer(byte[] input, int inOff, int len)`
    `protected void` | `ensureSufficientOutputBuffer(byte[] output, int outOff, int len)`
    `protected void` | `finishAAD(AEADBaseEngine.State nextState, boolean isDoFinal)`
    `protected void` | `finishAAD1(AEADBaseEngine.State nextState)`
    `protected void` | `finishAAD2(AEADBaseEngine.State nextState)`
    `protected void` | `finishAAD3(AEADBaseEngine.State nextState, boolean isDoFinal)`
    `java.lang.String` | `getAlgorithmName()` Return the name of the algorithm.
    `int` | `getBlockSize()`
    `int` | `getIVBytesSize()`
    `int` | `getKeyBytesSize()`
    `byte[]` | `getMac()` Return the value of the MAC associated with the last stream processed.
    `int` | `getOutputSize(int len)` return the size of the output buffer required for a processBytes plus a doFinal with an input of len bytes.
    `protected int` | `getTotalBytesForUpdate(int len)`
    `int` | `getUpdateOutputSize(int len)` return the size of the output buffer required for a processBytes an input of len bytes.
    `void` | `init(boolean forEncryption, CipherParameters params)` initialise the underlying cipher.
    `protected void` | `init(byte[] key, byte[] iv)`
    `void` | `processAADByte(byte input)` Add a single byte to the associated data check.
    `void` | `processAADBytes(byte[] input, int inOff, int len)` Add a sequence of bytes to the associated data check.
    `protected void` | `processBufferAAD(byte[] input, int inOff)`
    `protected void` | `processBufferDecrypt(byte[] input, int inOff, byte[] output, int outOff)`
    `protected void` | `processBufferEncrypt(byte[] input, int inOff, byte[] output, int outOff)`
    `int` | `processByte(byte in, byte[] out, int outOff)` encrypt/decrypt a single byte.
    `int` | `processBytes(byte[] input, int inOff, int len, byte[] output, int outOff)` process a block of bytes from in putting the result into out.
    `protected int` | `processEncDecByte(byte[] output, int outOff)`
    `protected int` | `processEncDecBytes(byte[] input, int inOff, int len, byte[] output, int outOff)`
    `protected void` | `processFinalAAD()`
    `protected void` | `processFinalBlock(byte[] output, int outOff)`
    `void` | `reset()` Reset the cipher.
    `protected void` | `reset(boolean clearMac)`
    `protected void` | `setInnerMembers(AEADBaseEngine.ProcessingBufferType type, AEADBaseEngine.AADOperatorType aadOperatorType, AEADBaseEngine.DataOperatorType dataOperatorType)`

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

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

- - ### Field Detail

    - #### forEncryption

          protected boolean forEncryption

    - #### algorithmName

          protected java.lang.String algorithmName

    - #### KEY_SIZE

          protected int KEY_SIZE

    - #### IV_SIZE

          protected int IV_SIZE

    - #### MAC_SIZE

          protected int MAC_SIZE

    - #### macSizeLowerBound

          protected int macSizeLowerBound

    - #### initialAssociatedText

          protected byte[] initialAssociatedText

    - #### mac

          protected byte[] mac

    - #### m_buf

          protected byte[] m_buf

    - #### m_aad

          protected byte[] m_aad

    - #### m_bufPos

          protected int m_bufPos

    - #### m_aadPos

          protected int m_aadPos

    - #### AADBufferSize

          protected int AADBufferSize

    - #### BlockSize

          protected int BlockSize

    - #### m_state

          protected AEADBaseEngine.State m_state

    - #### m_bufferSizeDecrypt

          protected int m_bufferSizeDecrypt

    - #### processor

          protected org.bouncycastle.crypto.engines.AEADBaseEngine.AADProcessingBuffer processor

    - #### aadOperator

          protected AEADBaseEngine.AADOperator aadOperator

    - #### dataOperator

          protected AEADBaseEngine.DataOperator dataOperator

    - #### decryptionFailureCounter

          protected AEADBaseEngine.DecryptionFailureCounter decryptionFailureCounter

    - #### dataLimitCounter

          protected AEADBaseEngine.DataLimitCounter dataLimitCounter

  - ### Constructor Detail

    - #### ISAPEngine

          public ISAPEngine(ISAPEngine.IsapType isapType)

  - ### Method Detail

    - #### init

          protected void init(byte[] key,
                              byte[] iv)
                       throws java.lang.IllegalArgumentException

      Throws:
        `java.lang.IllegalArgumentException`

    - #### processBufferAAD

          protected void processBufferAAD(byte[] input,
                                          int inOff)

    - #### processFinalAAD

          protected void processFinalAAD()

    - #### finishAAD

          protected void finishAAD(AEADBaseEngine.State nextState,
                                   boolean isDoFinal)

    - #### processBufferEncrypt

          protected void processBufferEncrypt(byte[] input,
                                              int inOff,
                                              byte[] output,
                                              int outOff)

    - #### processBufferDecrypt

          protected void processBufferDecrypt(byte[] input,
                                              int inOff,
                                              byte[] output,
                                              int outOff)

    - #### processFinalBlock

          protected void processFinalBlock(byte[] output,
                                           int outOff)

    - #### reset

          protected void reset(boolean clearMac)

    - #### getAlgorithmName

          public java.lang.String getAlgorithmName()

      Description copied from interface: `AEADCipher`
      Return the name of the algorithm.
      Specified by:
        `getAlgorithmName` in interface `AEADCipher`
      Returns:
        the algorithm name.

    - #### getKeyBytesSize

          public int getKeyBytesSize()

    - #### getIVBytesSize

          public int getIVBytesSize()

    - #### getMac

          public byte[] getMac()

      Description copied from interface: `AEADCipher`
      Return the value of the MAC associated with the last stream processed.
      Specified by:
        `getMac` in interface `AEADCipher`
      Returns:
        MAC for plaintext data.

    - #### init

          public void init(boolean forEncryption,
                           CipherParameters params)

      Description copied from interface: `AEADCipher`
      initialise the underlying cipher. Parameter can either be an AEADParameters or a ParametersWithIV object.
      Specified by:
        `init` in interface `AEADCipher`
      Parameters:
        `forEncryption` - true if we are setting up for encryption, false otherwise.
        `params` - the necessary parameters for the underlying cipher to be initialised.

    - #### reset

          public void reset()

      Description copied from interface: `AEADCipher`
      Reset the cipher. After resetting the cipher is in the same state as it was after the last init (if there was one).
      Specified by:
        `reset` in interface `AEADCipher`

    - #### setInnerMembers

          protected void setInnerMembers(AEADBaseEngine.ProcessingBufferType type,
                                         AEADBaseEngine.AADOperatorType aadOperatorType,
                                         AEADBaseEngine.DataOperatorType dataOperatorType)

    - #### processAADByte

          public void processAADByte(byte input)

      Description copied from interface: `AEADCipher`
      Add a single byte to the associated data check.
      If the implementation supports it, this will be an online operation and will not retain the associated data.
      Specified by:
        `processAADByte` in interface `AEADCipher`
      Parameters:
        `input` - the byte to be processed.

    - #### processAADBytes

          public void processAADBytes(byte[] input,
                                      int inOff,
                                      int len)

      Description copied from interface: `AEADCipher`
      Add a sequence of bytes to the associated data check.
      If the implementation supports it, this will be an online operation and will not retain the associated data.
      Specified by:
        `processAADBytes` in interface `AEADCipher`
      Parameters:
        `input` - the input byte array.
        `inOff` - the offset into the in array where the data to be processed starts.
        `len` - the number of bytes to be processed.

    - #### processByte

          public int processByte(byte in,
                                 byte[] out,
                                 int outOff)
                          throws DataLengthException

      Description copied from interface: `AEADCipher`
      encrypt/decrypt a single byte.
      Specified by:
        `processByte` in interface `AEADCipher`
      Parameters:
        `in` - the byte to be processed.
        `out` - the output buffer the processed byte goes into.
        `outOff` - the offset into the output byte array the processed data starts at.
      Returns:
        the number of bytes written to out.
      Throws:
        `DataLengthException` - if the output buffer is too small.

    - #### processEncDecByte

          protected int processEncDecByte(byte[] output,
                                          int outOff)

    - #### processBytes

          public int processBytes(byte[] input,
                                  int inOff,
                                  int len,
                                  byte[] output,
                                  int outOff)
                           throws DataLengthException

      Description copied from interface: `AEADCipher`
      process a block of bytes from in putting the result into out.
      Specified by:
        `processBytes` in interface `AEADCipher`
      Parameters:
        `input` - the input byte array.
        `inOff` - the offset into the in array where the data to be processed starts.
        `len` - the number of bytes to be processed.
        `output` - the output buffer the processed bytes go into.
        `outOff` - the offset into the output byte array the processed data starts at.
      Returns:
        the number of bytes written to out.
      Throws:
        `DataLengthException` - if the output buffer is too small.

    - #### processEncDecBytes

          protected int processEncDecBytes(byte[] input,
                                           int inOff,
                                           int len,
                                           byte[] output,
                                           int outOff)

    - #### doFinal

          public int doFinal(byte[] output,
                             int outOff)
                      throws java.lang.IllegalStateException,
                             InvalidCipherTextException

      Description copied from interface: `AEADCipher`
      Finish the operation either appending or verifying the MAC at the end of the data.
      Specified by:
        `doFinal` in interface `AEADCipher`
      Parameters:
        `output` - space for any resulting output data.
        `outOff` - offset into out to start copying the data at.
      Returns:
        number of bytes written into out.
      Throws:
        `java.lang.IllegalStateException` - if the cipher is in an inappropriate state.
        `InvalidCipherTextException` - if the MAC fails to match.

    - #### getBlockSize

          public final int getBlockSize()

    - #### getUpdateOutputSize

          public int getUpdateOutputSize(int len)

      Description copied from interface: `AEADCipher`
      return the size of the output buffer required for a processBytes an input of len bytes.

      The returned size may be dependent on the initialisation of this cipher and may not be accurate once subsequent input data is processed - this method should be invoked immediately prior to input data being processed.

      Specified by:
        `getUpdateOutputSize` in interface `AEADCipher`
      Parameters:
        `len` - the length of the input.
      Returns:
        the space required to accommodate a call to processBytes with len bytes of input.

    - #### getTotalBytesForUpdate

          protected int getTotalBytesForUpdate(int len)

    - #### getOutputSize

          public int getOutputSize(int len)

      Description copied from interface: `AEADCipher`
      return the size of the output buffer required for a processBytes plus a doFinal with an input of len bytes.

      The returned size may be dependent on the initialisation of this cipher and may not be accurate once subsequent input data is processed - this method should be invoked immediately prior to a call to final processing of input data and a call to `AEADCipher.doFinal(byte[], int)`.

      Specified by:
        `getOutputSize` in interface `AEADCipher`
      Parameters:
        `len` - the length of the input.
      Returns:
        the space required to accommodate a call to processBytes and doFinal with len bytes of input.

    - #### checkAAD

          protected void checkAAD()

    - #### checkData

          protected boolean checkData(boolean isDoFinal)

    - #### ensureSufficientOutputBuffer

          protected final void ensureSufficientOutputBuffer(byte[] output,
                                                            int outOff,
                                                            int len)

    - #### ensureSufficientInputBuffer

          protected final void ensureSufficientInputBuffer(byte[] input,
                                                           int inOff,
                                                           int len)

    - #### ensureInitialized

          protected final void ensureInitialized()

    - #### finishAAD1

          protected void finishAAD1(AEADBaseEngine.State nextState)

    - #### finishAAD2

          protected void finishAAD2(AEADBaseEngine.State nextState)

    - #### finishAAD3

          protected void finishAAD3(AEADBaseEngine.State nextState,
                                    boolean isDoFinal)