Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Ctors](https://developer.android.com/reference/javax/crypto/CipherSpi#pubctors) \| [Protected Methods](https://developer.android.com/reference/javax/crypto/CipherSpi#promethods) \| [Inherited Methods](https://developer.android.com/reference/javax/crypto/CipherSpi#inhmethods)

# CipherSpi


`
public


abstract
class
CipherSpi
`


`

extends https://developer.android.com/reference/java/lang/Object


`

`


`

|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||
| ↳ | javax.crypto.CipherSpi |

<br />

*** ** * ** ***

This class defines the *Service Provider Interface* (**SPI** )
for the `Cipher` class.
All the abstract methods in this class must be implemented by each
cryptographic service provider who wishes to supply the implementation
of a particular cipher algorithm.

In order to create an instance of `Cipher`, which
encapsulates an instance of this `CipherSpi` class, an
application calls one of the
`https://developer.android.com/reference/javax/crypto/Cipher#getInstance(java.lang.String)`
factory methods of the
`https://developer.android.com/reference/javax/crypto/Cipher` engine class and specifies the requested
*transformation*.
Optionally, the application may also specify the name of a provider.

A *transformation* is a string that describes the operation (or
set of operations) to be performed on the given input, to produce some
output. A transformation always includes the name of a cryptographic
algorithm (e.g., *DES*), and may be followed by a feedback mode and
padding scheme.

A transformation is of the form:

- "*algorithm/mode/padding*" or
- "*algorithm*"

(in the latter case,
provider-specific default values for the mode and padding scheme are used).
For example, the following is a valid transformation:

    Cipher c = Cipher.getInstance("DES/CBC/PKCS5Padding");

A provider may supply a separate class for each combination
of *algorithm/mode/padding*, or may decide to provide more generic
classes representing sub-transformations corresponding to
*algorithm* or *algorithm/mode* or *algorithm//padding*
(note the double slashes),
in which case the requested mode and/or padding are set automatically by
the `getInstance` methods of `Cipher`, which invoke
the `https://developer.android.com/reference/javax/crypto/CipherSpi#engineSetMode(java.lang.String)` and
`https://developer.android.com/reference/javax/crypto/CipherSpi#engineSetPadding(java.lang.String)`
methods of the provider's subclass of `CipherSpi`.

A `Cipher` property in a provider master class may have one of
the following formats:

-

          // provider's subclass of "CipherSpi" implements "algName" with
          // pluggable mode and padding
          Cipher.algName

-

          // provider's subclass of "CipherSpi" implements "algName" in the
          // specified "mode", with pluggable padding
          Cipher.algName/mode

-

          // provider's subclass of "CipherSpi" implements "algName" with the
          // specified "padding", with pluggable mode
          Cipher.algName//padding

-

          // provider's subclass of "CipherSpi" implements "algName" with the
          // specified "mode" and "padding"
          Cipher.algName/mode/padding

For example, a provider may supply a subclass of `CipherSpi`
that implements *DES/ECB/PKCS5Padding*, one that implements
*DES/CBC/PKCS5Padding*, one that implements
*DES/CFB/PKCS5Padding*, and yet another one that implements
*DES/OFB/PKCS5Padding*. That provider would have the following
`Cipher` properties in its master class:

-

          Cipher.DES/ECB/PKCS5Padding

-

          Cipher.DES/CBC/PKCS5Padding

-

          Cipher.DES/CFB/PKCS5Padding

-

          Cipher.DES/OFB/PKCS5Padding

Another provider may implement a class for each of the above modes
(i.e., one class for *ECB*, one for *CBC*, one for *CFB*,
and one for *OFB*), one class for *PKCS5Padding*,
and a generic *DES* class that subclasses from `CipherSpi`.
That provider would have the following
`Cipher` properties in its master class:

-

          Cipher.DES

The `getInstance` factory method of the `Cipher`
engine class follows these rules in order to instantiate a provider's
implementation of `CipherSpi` for a
transformation of the form "*algorithm*":

1. Check if the provider has registered a subclass of `CipherSpi` for the specified "*algorithm*".

   If the answer is YES, instantiate this
   class, for whose mode and padding scheme default values (as supplied by
   the provider) are used.

   If the answer is NO, throw a `NoSuchAlgorithmException`
   exception.

The `getInstance` factory method of the `Cipher`
engine class follows these rules in order to instantiate a provider's
implementation of `CipherSpi` for a
transformation of the form "*algorithm/mode/padding*":

1. Check if the provider has registered a subclass of `CipherSpi` for the specified "*algorithm/mode/padding*" transformation.

   If the answer is YES, instantiate it.

   If the answer is NO, go to the next step.
2. Check if the provider has registered a subclass of `CipherSpi` for the sub-transformation "*algorithm/mode*".

   If the answer is YES, instantiate it, and call
   `engineSetPadding(*padding*)` on the new instance.

   If the answer is NO, go to the next step.
3. Check if the provider has registered a subclass of `CipherSpi` for the sub-transformation "*algorithm//padding*" (note the double slashes).

   If the answer is YES, instantiate it, and call
   `engineSetMode(*mode*)` on the new instance.

   If the answer is NO, go to the next step.
4. Check if the provider has registered a subclass of `CipherSpi` for the sub-transformation "*algorithm*".

   If the answer is YES, instantiate it, and call
   `engineSetMode(*mode*)` and
   `engineSetPadding(*padding*)` on the new instance.

   If the answer is NO, throw a `NoSuchAlgorithmException`
   exception.

<br />

**See also:**

- `https://developer.android.com/reference/javax/crypto/KeyGenerator`
- `https://developer.android.com/reference/javax/crypto/SecretKey`

## Summary

| ### Public constructors ||
|---|---|
| ` https://developer.android.com/reference/javax/crypto/CipherSpi#CipherSpi()() ` |

| ### Protected methods ||
|---|---|
| ` abstract int` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineDoFinal(byte[],%20int,%20int,%20byte[],%20int)(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) ` Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. |
| ` int` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineDoFinal(java.nio.ByteBuffer,%20java.nio.ByteBuffer)(https://developer.android.com/reference/java/nio/ByteBuffer input, https://developer.android.com/reference/java/nio/ByteBuffer output) ` Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. |
| ` abstract byte[]` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineDoFinal(byte[],%20int,%20int)(byte[] input, int inputOffset, int inputLen) ` Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation. |
| ` abstract int` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetBlockSize()() ` Returns the block size (in bytes). |
| ` abstract byte[]` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetIV()() ` Returns the initialization vector (IV) in a new buffer. |
| ` int` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetKeySize(java.security.Key)(https://developer.android.com/reference/java/security/Key key) ` Returns the key size of the given key object in bits. |
| ` abstract int` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetOutputSize(int)(int inputLen) ` Returns the length in bytes that an output buffer would need to be in order to hold the result of the next `update` or `doFinal` operation, given the input length `inputLen` (in bytes). |
| ` abstract https://developer.android.com/reference/java/security/AlgorithmParameters` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetParameters()() ` Returns the parameters used with this cipher. |
| ` abstract void` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineInit(int,%20java.security.Key,%20java.security.SecureRandom)(int opmode, https://developer.android.com/reference/java/security/Key key, https://developer.android.com/reference/java/security/SecureRandom random) ` Initializes this cipher with a key and a source of randomness. |
| ` abstract void` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineInit(int,%20java.security.Key,%20java.security.spec.AlgorithmParameterSpec,%20java.security.SecureRandom)(int opmode, https://developer.android.com/reference/java/security/Key key, https://developer.android.com/reference/java/security/spec/AlgorithmParameterSpec params, https://developer.android.com/reference/java/security/SecureRandom random) ` Initializes this cipher with a key, a set of algorithm parameters, and a source of randomness. |
| ` abstract void` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineInit(int,%20java.security.Key,%20java.security.AlgorithmParameters,%20java.security.SecureRandom)(int opmode, https://developer.android.com/reference/java/security/Key key, https://developer.android.com/reference/java/security/AlgorithmParameters params, https://developer.android.com/reference/java/security/SecureRandom random) ` Initializes this cipher with a key, a set of algorithm parameters, and a source of randomness. |
| ` abstract void` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineSetMode(java.lang.String)(https://developer.android.com/reference/java/lang/String mode) ` Sets the mode of this cipher. |
| ` abstract void` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineSetPadding(java.lang.String)(https://developer.android.com/reference/java/lang/String padding) ` Sets the padding mechanism of this cipher. |
| ` https://developer.android.com/reference/java/security/Key` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineUnwrap(byte[],%20java.lang.String,%20int)(byte[] wrappedKey, https://developer.android.com/reference/java/lang/String wrappedKeyAlgorithm, int wrappedKeyType) ` Unwrap a previously wrapped key. |
| ` abstract byte[]` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineUpdate(byte[],%20int,%20int)(byte[] input, int inputOffset, int inputLen) ` Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part. |
| ` abstract int` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineUpdate(byte[],%20int,%20int,%20byte[],%20int)(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset) ` Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part. |
| ` int` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineUpdate(java.nio.ByteBuffer,%20java.nio.ByteBuffer)(https://developer.android.com/reference/java/nio/ByteBuffer input, https://developer.android.com/reference/java/nio/ByteBuffer output) ` Continues a multiple-part encryption or decryption operation (depending on how this cipher was initialized), processing another data part. |
| ` void` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineUpdateAAD(byte[],%20int,%20int)(byte[] src, int offset, int len) ` Continues a multi-part update of the Additional Authentication Data (AAD), using a subset of the provided buffer. |
| ` void` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineUpdateAAD(java.nio.ByteBuffer)(https://developer.android.com/reference/java/nio/ByteBuffer src) ` Continues a multi-part update of the Additional Authentication Data (AAD). |
| ` byte[]` | ` https://developer.android.com/reference/javax/crypto/CipherSpi#engineWrap(java.security.Key)(https://developer.android.com/reference/java/security/Key key) ` Wrap a key. |

| ### Inherited methods |
|---|---|
| From class ` https://developer.android.com/reference/java/lang/Object ` |---|---| | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/lang/Object#clone()() ` Creates and returns a copy of this object. | | ` boolean` | ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` https://developer.android.com/reference/java/lang/Object#finalize()() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final https://developer.android.com/reference/java/lang/Class<?>` | ` https://developer.android.com/reference/java/lang/Object#getClass()() ` Returns the runtime class of this `Object`. | | ` int` | ` https://developer.android.com/reference/java/lang/Object#hashCode()() ` Returns a hash code value for the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notify()() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notifyAll()() ` Wakes up all threads that are waiting on this object's monitor. | | ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/lang/Object#toString()() ` Returns a string representation of the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait()() ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*. | ||

## Public constructors

### CipherSpi

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public CipherSpi ()
```

<br />

<br />

## Protected methods

### engineDoFinal

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract int engineDoFinal (byte[] input, 
                int inputOffset, 
                int inputLen, 
                byte[] output, 
                int outputOffset)
```

Encrypts or decrypts data in a single-part operation,
or finishes a multiple-part operation.
The data is encrypted or decrypted, depending on how this cipher was
initialized.

The first `inputLen` bytes in the `input`
buffer, starting at `inputOffset` inclusive, and any input
bytes that may have been buffered during a previous `update`
operation, are processed, with padding (if requested) being applied.
If an AEAD mode such as GCM/CCM is being used, the authentication
tag is appended in the case of encryption, or verified in the
case of decryption.
The result is stored in the `output` buffer, starting at
`outputOffset` inclusive.

If the `output` buffer is too small to hold the result,
a `ShortBufferException` is thrown.

Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to
`engineInit`.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
`engineInit`) more data.

Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.

<br />

| Parameters ||
|---|---|
| `input` | `byte`: the input buffer <br /> |
| `inputOffset` | `int`: the offset in `input` where the input starts <br /> |
| `inputLen` | `int`: the input length <br /> |
| `output` | `byte`: the buffer for the result <br /> |
| `outputOffset` | `int`: the offset in `output` where the result is stored <br /> |

| Returns ||
|---|---|
| `int` | the number of bytes stored in `output` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/javax/crypto/AEADBadTagException` | if this cipher is decrypting in an AEAD mode (such as GCM/CCM), and the received authentication tag does not match the calculated value |
| `https://developer.android.com/reference/javax/crypto/BadPaddingException` | if this cipher is in decryption mode, and (un)padding has been requested, but the decrypted data is not bounded by the appropriate padding bytes |
| `https://developer.android.com/reference/javax/crypto/IllegalBlockSizeException` | if this cipher is a block cipher, no padding has been requested (only in encryption mode), and the total input length of the data processed by this cipher is not a multiple of block size; or if this encryption algorithm is unable to process the input data provided. |
| `https://developer.android.com/reference/javax/crypto/ShortBufferException` | if the given output buffer is too small to hold the result |

### engineDoFinal

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected int engineDoFinal (ByteBuffer input, 
                ByteBuffer output)
```

Encrypts or decrypts data in a single-part operation,
or finishes a multiple-part operation.
The data is encrypted or decrypted, depending on how this cipher was
initialized.

All `input.remaining()` bytes starting at
`input.position()` are processed.
If an AEAD mode such as GCM/CCM is being used, the authentication
tag is appended in the case of encryption, or verified in the
case of decryption.
The result is stored in the output buffer.
Upon return, the input buffer's position will be equal
to its limit; its limit will not have changed. The output buffer's
position will have advanced by n, where n is the value returned
by this method; the output buffer's limit will not have changed.

If `output.remaining()` bytes are insufficient to
hold the result, a `ShortBufferException` is thrown.

Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to
`engineInit`.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
`engineInit`) more data.

Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.

Subclasses should consider overriding this method if they can
process ByteBuffers more efficiently than byte arrays.

<br />

| Parameters ||
|---|---|
| `input` | `ByteBuffer`: the input ByteBuffer <br /> |
| `output` | `ByteBuffer`: the output ByteByffer <br /> |

| Returns ||
|---|---|
| `int` | the number of bytes stored in `output` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if either parameter is `null` |
| `https://developer.android.com/reference/javax/crypto/AEADBadTagException` | if this cipher is decrypting in an AEAD mode (such as GCM/CCM), and the received authentication tag does not match the calculated value |
| `https://developer.android.com/reference/javax/crypto/BadPaddingException` | if this cipher is in decryption mode, and (un)padding has been requested, but the decrypted data is not bounded by the appropriate padding bytes |
| `https://developer.android.com/reference/javax/crypto/IllegalBlockSizeException` | if this cipher is a block cipher, no padding has been requested (only in encryption mode), and the total input length of the data processed by this cipher is not a multiple of block size; or if this encryption algorithm is unable to process the input data provided. |
| `https://developer.android.com/reference/javax/crypto/ShortBufferException` | if there is insufficient space in the output buffer |

### engineDoFinal

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract byte[] engineDoFinal (byte[] input, 
                int inputOffset, 
                int inputLen)
```

Encrypts or decrypts data in a single-part operation,
or finishes a multiple-part operation.
The data is encrypted or decrypted, depending on how this cipher was
initialized.

The first `inputLen` bytes in the `input`
buffer, starting at `inputOffset` inclusive, and any input
bytes that may have been buffered during a previous `update`
operation, are processed, with padding (if requested) being applied.
If an AEAD mode such as GCM/CCM is being used, the authentication
tag is appended in the case of encryption, or verified in the
case of decryption.
The result is stored in a new buffer.

Upon finishing, this method resets this cipher object to the state
it was in when previously initialized via a call to
`engineInit`.
That is, the object is reset and available to encrypt or decrypt
(depending on the operation mode that was specified in the call to
`engineInit`) more data.

Note: if any exception is thrown, this cipher object may need to
be reset before it can be used again.

<br />

| Parameters ||
|---|---|
| `input` | `byte`: the input buffer <br /> |
| `inputOffset` | `int`: the offset in `input` where the input starts <br /> |
| `inputLen` | `int`: the input length <br /> |

| Returns ||
|---|---|
| `byte[]` | the new buffer with the result <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/javax/crypto/AEADBadTagException` | if this cipher is decrypting in an AEAD mode (such as GCM/CCM), and the received authentication tag does not match the calculated value |
| `https://developer.android.com/reference/javax/crypto/BadPaddingException` | if this cipher is in decryption mode, and (un)padding has been requested, but the decrypted data is not bounded by the appropriate padding bytes |
| `https://developer.android.com/reference/javax/crypto/IllegalBlockSizeException` | if this cipher is a block cipher, no padding has been requested (only in encryption mode), and the total input length of the data processed by this cipher is not a multiple of block size; or if this encryption algorithm is unable to process the input data provided. |

### engineGetBlockSize

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract int engineGetBlockSize ()
```

Returns the block size (in bytes).

<br />

| Returns ||
|---|---|
| `int` | the block size (in bytes), or 0 if the underlying algorithm is not a block cipher <br /> |

### engineGetIV

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract byte[] engineGetIV ()
```

Returns the initialization vector (IV) in a new buffer.

This is useful in the context of password-based encryption or
decryption, where the IV is derived from a user-provided passphrase.

<br />

| Returns ||
|---|---|
| `byte[]` | the initialization vector in a new buffer, or null if the underlying algorithm does not use an IV, or if the IV has not yet been set. <br /> |

### engineGetKeySize

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected int engineGetKeySize (Key key)
```

Returns the key size of the given key object in bits.

This concrete method has been added to this previously-defined
abstract class. It throws an `UnsupportedOperationException`
if it is not overridden by the provider.

<br />

| Parameters ||
|---|---|
| `key` | `Key`: the key object. <br /> |

| Returns ||
|---|---|
| `int` | the key size of the given key object. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/security/InvalidKeyException` | if `key` is invalid. |

### engineGetOutputSize

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract int engineGetOutputSize (int inputLen)
```

Returns the length in bytes that an output buffer would
need to be in order to hold the result of the next `update`
or `doFinal` operation, given the input length
`inputLen` (in bytes).

This call takes into account any unprocessed (buffered) data from a
previous `update` call, padding, and AEAD tagging.

The actual output length of the next `update` or
`doFinal` call may be smaller than the length returned by
this method.

<br />

| Parameters ||
|---|---|
| `inputLen` | `int`: the input length (in bytes) <br /> |

| Returns ||
|---|---|
| `int` | the required output buffer size (in bytes) <br /> |

### engineGetParameters

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract AlgorithmParameters engineGetParameters ()
```

Returns the parameters used with this cipher.

The returned parameters may be the same that were used to initialize
this cipher, or may contain a combination of default and random
parameter values used by the underlying cipher implementation if this
cipher requires algorithm parameters but was not initialized with any.

<br />

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/security/AlgorithmParameters` | the parameters used with this cipher, or null if this cipher does not use any parameters. <br /> |

### engineInit

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract void engineInit (int opmode, 
                Key key, 
                SecureRandom random)
```

Initializes this cipher with a key and a source
of randomness.

The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or key unwrapping, depending on
the value of `opmode`.

If this cipher requires any algorithm parameters that cannot be
derived from the given `key`, the underlying cipher
implementation is supposed to generate the required parameters itself
(using provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
`InvalidKeyException` if it is being
initialized for decryption or key unwrapping.
The generated parameters can be retrieved using
`https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetParameters()` or
`https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetIV()` (if the parameter is an IV).

If this cipher requires algorithm parameters that cannot be
derived from the input parameters, and there are no reasonable
provider-specific default values, initialization will
necessarily fail.

If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from `random`.

Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.

<br />

| Parameters ||
|---|---|
| `opmode` | `int`: the operation mode of this cipher (this is one of the following: `ENCRYPT_MODE`, `DECRYPT_MODE`, `WRAP_MODE` or `UNWRAP_MODE`) <br /> |
| `key` | `Key`: the encryption key <br /> |
| `random` | `SecureRandom`: the source of randomness <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if `opmode` is `WRAP_MODE` or `UNWRAP_MODE` is not implemented by the cipher. |
| `https://developer.android.com/reference/java/security/InvalidKeyException` | if the given key is inappropriate for initializing this cipher, or requires algorithm parameters that cannot be determined from the given key. |

### engineInit

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract void engineInit (int opmode, 
                Key key, 
                AlgorithmParameterSpec params, 
                SecureRandom random)
```

Initializes this cipher with a key, a set of
algorithm parameters, and a source of randomness.

The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or key unwrapping, depending on
the value of `opmode`.

If this cipher requires any algorithm parameters and
`params` is null, the underlying cipher implementation is
supposed to generate the required parameters itself (using
provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
`InvalidAlgorithmParameterException` if it is being
initialized for decryption or key unwrapping.
The generated parameters can be retrieved using
`https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetParameters()` or
`https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetIV()` (if the parameter is an IV).

If this cipher requires algorithm parameters that cannot be
derived from the input parameters, and there are no reasonable
provider-specific default values, initialization will
necessarily fail.

If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from `random`.

Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.

<br />

| Parameters ||
|---|---|
| `opmode` | `int`: the operation mode of this cipher (this is one of the following: `ENCRYPT_MODE`, `DECRYPT_MODE`, `WRAP_MODE` or `UNWRAP_MODE`) <br /> |
| `key` | `Key`: the encryption key <br /> |
| `params` | `AlgorithmParameterSpec`: the algorithm parameters <br /> |
| `random` | `SecureRandom`: the source of randomness <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if `opmode` is `WRAP_MODE` or `UNWRAP_MODE` is not implemented by the cipher. |
| `https://developer.android.com/reference/java/security/InvalidAlgorithmParameterException` | if the given algorithm parameters are inappropriate for this cipher, or if this cipher requires algorithm parameters and `params` is null. |
| `https://developer.android.com/reference/java/security/InvalidKeyException` | if the given key is inappropriate for initializing this cipher |

### engineInit

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract void engineInit (int opmode, 
                Key key, 
                AlgorithmParameters params, 
                SecureRandom random)
```

Initializes this cipher with a key, a set of
algorithm parameters, and a source of randomness.

The cipher is initialized for one of the following four operations:
encryption, decryption, key wrapping or key unwrapping, depending on
the value of `opmode`.

If this cipher requires any algorithm parameters and
`params` is null, the underlying cipher implementation is
supposed to generate the required parameters itself (using
provider-specific default or random values) if it is being
initialized for encryption or key wrapping, and raise an
`InvalidAlgorithmParameterException` if it is being
initialized for decryption or key unwrapping.
The generated parameters can be retrieved using
`https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetParameters()` or
`https://developer.android.com/reference/javax/crypto/CipherSpi#engineGetIV()` (if the parameter is an IV).

If this cipher requires algorithm parameters that cannot be
derived from the input parameters, and there are no reasonable
provider-specific default values, initialization will
necessarily fail.

If this cipher (including its underlying feedback or padding scheme)
requires any random bytes (e.g., for parameter generation), it will get
them from `random`.

Note that when a Cipher object is initialized, it loses all
previously-acquired state. In other words, initializing a Cipher is
equivalent to creating a new instance of that Cipher and initializing
it.

<br />

| Parameters ||
|---|---|
| `opmode` | `int`: the operation mode of this cipher (this is one of the following: `ENCRYPT_MODE`, `DECRYPT_MODE`, `WRAP_MODE` or `UNWRAP_MODE`) <br /> |
| `key` | `Key`: the encryption key <br /> |
| `params` | `AlgorithmParameters`: the algorithm parameters <br /> |
| `random` | `SecureRandom`: the source of randomness <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if `opmode` is `WRAP_MODE` or `UNWRAP_MODE` is not implemented by the cipher. |
| `https://developer.android.com/reference/java/security/InvalidAlgorithmParameterException` | if the given algorithm parameters are inappropriate for this cipher, or if this cipher requires algorithm parameters and `params` is null. |
| `https://developer.android.com/reference/java/security/InvalidKeyException` | if the given key is inappropriate for initializing this cipher |

### engineSetMode

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract void engineSetMode (String mode)
```

Sets the mode of this cipher.

<br />

| Parameters ||
|---|---|
| `mode` | `String`: the cipher mode <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/security/NoSuchAlgorithmException` | if the requested cipher mode does not exist |

### engineSetPadding

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract void engineSetPadding (String padding)
```

Sets the padding mechanism of this cipher.

<br />

| Parameters ||
|---|---|
| `padding` | `String`: the padding mechanism <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/javax/crypto/NoSuchPaddingException` | if the requested padding mechanism does not exist |

### engineUnwrap

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected Key engineUnwrap (byte[] wrappedKey, 
                String wrappedKeyAlgorithm, 
                int wrappedKeyType)
```

Unwrap a previously wrapped key.

This concrete method has been added to this previously-defined
abstract class. (For backwards compatibility, it cannot be abstract.)
It may be overridden by a provider to unwrap a previously wrapped key.
Such an override is expected to throw an InvalidKeyException if
the given wrapped key cannot be unwrapped.
If this method is not overridden, it always throws an
UnsupportedOperationException.

<br />

| Parameters ||
|---|---|
| `wrappedKey` | `byte`: the key to be unwrapped. <br /> |
| `wrappedKeyAlgorithm` | `String`: the algorithm associated with the wrapped key. <br /> |
| `wrappedKeyType` | `int`: the type of the wrapped key. This is one of `SECRET_KEY`, `PRIVATE_KEY`, or `PUBLIC_KEY`. <br /> |

| Returns ||
|---|---|
| `https://developer.android.com/reference/java/security/Key` | the unwrapped key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if this method is not supported. |
| `https://developer.android.com/reference/java/security/InvalidKeyException` | if `wrappedKey` does not represent a wrapped key of type `wrappedKeyType` for the `wrappedKeyAlgorithm`. |
| `https://developer.android.com/reference/java/security/NoSuchAlgorithmException` | if no installed providers can create keys of type `wrappedKeyType` for the `wrappedKeyAlgorithm`. |

### engineUpdate

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract byte[] engineUpdate (byte[] input, 
                int inputOffset, 
                int inputLen)
```

Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.

The first `inputLen` bytes in the `input`
buffer, starting at `inputOffset` inclusive, are processed,
and the result is stored in a new buffer.

<br />

| Parameters ||
|---|---|
| `input` | `byte`: the input buffer <br /> |
| `inputOffset` | `int`: the offset in `input` where the input starts <br /> |
| `inputLen` | `int`: the input length <br /> |

| Returns ||
|---|---|
| `byte[]` | the new buffer with the result, or null if the underlying cipher is a block cipher and the input data is too short to result in a new block. <br /> |

### engineUpdate

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected abstract int engineUpdate (byte[] input, 
                int inputOffset, 
                int inputLen, 
                byte[] output, 
                int outputOffset)
```

Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.

The first `inputLen` bytes in the `input`
buffer, starting at `inputOffset` inclusive, are processed,
and the result is stored in the `output` buffer, starting at
`outputOffset` inclusive.

If the `output` buffer is too small to hold the result,
a `ShortBufferException` is thrown.

<br />

| Parameters ||
|---|---|
| `input` | `byte`: the input buffer <br /> |
| `inputOffset` | `int`: the offset in `input` where the input starts <br /> |
| `inputLen` | `int`: the input length <br /> |
| `output` | `byte`: the buffer for the result <br /> |
| `outputOffset` | `int`: the offset in `output` where the result is stored <br /> |

| Returns ||
|---|---|
| `int` | the number of bytes stored in `output` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/javax/crypto/ShortBufferException` | if the given output buffer is too small to hold the result |

### engineUpdate

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected int engineUpdate (ByteBuffer input, 
                ByteBuffer output)
```

Continues a multiple-part encryption or decryption operation
(depending on how this cipher was initialized), processing another data
part.

All `input.remaining()` bytes starting at
`input.position()` are processed. The result is stored
in the output buffer.
Upon return, the input buffer's position will be equal
to its limit; its limit will not have changed. The output buffer's
position will have advanced by n, where n is the value returned
by this method; the output buffer's limit will not have changed.

If `output.remaining()` bytes are insufficient to
hold the result, a `ShortBufferException` is thrown.

Subclasses should consider overriding this method if they can
process ByteBuffers more efficiently than byte arrays.

<br />

| Parameters ||
|---|---|
| `input` | `ByteBuffer`: the input ByteBuffer <br /> |
| `output` | `ByteBuffer`: the output ByteByffer <br /> |

| Returns ||
|---|---|
| `int` | the number of bytes stored in `output` <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/NullPointerException` | if either parameter is `null` |
| `https://developer.android.com/reference/javax/crypto/ShortBufferException` | if there is insufficient space in the output buffer |

### engineUpdateAAD

Added in [API level 19](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected void engineUpdateAAD (byte[] src, 
                int offset, 
                int len)
```

Continues a multi-part update of the Additional Authentication
Data (AAD), using a subset of the provided buffer.


Calls to this method provide AAD to the cipher when operating in
modes such as AEAD (GCM/CCM). If this cipher is operating in
either GCM or CCM mode, all AAD must be supplied before beginning
operations on the ciphertext (via the `update` and `doFinal` methods).

<br />

| Parameters ||
|---|---|
| `src` | `byte`: the buffer containing the AAD <br /> |
| `offset` | `int`: the offset in `src` where the AAD input starts <br /> |
| `len` | `int`: the number of AAD bytes <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this cipher is in a wrong state (e.g., has not been initialized), does not accept AAD, or if operating in either GCM or CCM mode and one of the `update` methods has already been called for the active encryption/decryption operation |
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if this method has not been overridden by an implementation |

### engineUpdateAAD

Added in [API level 19](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected void engineUpdateAAD (ByteBuffer src)
```

Continues a multi-part update of the Additional Authentication
Data (AAD).


Calls to this method provide AAD to the cipher when operating in
modes such as AEAD (GCM/CCM). If this cipher is operating in
either GCM or CCM mode, all AAD must be supplied before beginning
operations on the ciphertext (via the `update` and `doFinal` methods).


All `src.remaining()` bytes starting at
`src.position()` are processed.
Upon return, the input buffer's position will be equal
to its limit; its limit will not have changed.

<br />

| Parameters ||
|---|---|
| `src` | `ByteBuffer`: the buffer containing the AAD <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalStateException` | if this cipher is in a wrong state (e.g., has not been initialized), does not accept AAD, or if operating in either GCM or CCM mode and one of the `update` methods has already been called for the active encryption/decryption operation |
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if this method has not been overridden by an implementation |

### engineWrap

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected byte[] engineWrap (Key key)
```

Wrap a key.

This concrete method has been added to this previously-defined
abstract class. (For backwards compatibility, it cannot be abstract.)
It may be overridden by a provider to wrap a key.
Such an override is expected to throw an IllegalBlockSizeException or
InvalidKeyException (under the specified circumstances),
if the given key cannot be wrapped.
If this method is not overridden, it always throws an
UnsupportedOperationException.

<br />

| Parameters ||
|---|---|
| `key` | `Key`: the key to be wrapped. <br /> |

| Returns ||
|---|---|
| `byte[]` | the wrapped key. <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/UnsupportedOperationException` | if this method is not supported. |
| `https://developer.android.com/reference/java/security/InvalidKeyException` | if it is impossible or unsafe to wrap the key with this cipher (e.g., a hardware protected key is being passed to a software-only cipher). |
| `https://developer.android.com/reference/javax/crypto/IllegalBlockSizeException` | if this cipher is a block cipher, no padding has been requested, and the length of the encoding of the key to be wrapped is not a multiple of the block size. |