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openjdk / 21 / java.base / javax / crypto / cipher.html

Class Cipher

java.lang.Object
javax.crypto.Cipher
Direct Known Subclasses:
NullCipher 
public class Cipher extends Object
This class provides the functionality of a cryptographic cipher for encryption and decryption. It forms the core of the Java Cryptographic Extension (JCE) framework.

In order to create a Cipher object, the application calls the cipher's getInstance method, and passes the name of the requested transformation to it. Optionally, the name of a provider may be specified.

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., AES), 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("AES/CBC/PKCS5Padding");
Using modes such as CFB and OFB, block ciphers can encrypt data in units smaller than the cipher's actual block size. When requesting such a mode, you may optionally specify the number of bits to be processed at a time by appending this number to the mode name as shown in the "AES/CFB8/NoPadding" and "AES/OFB32/PKCS5Padding" transformations. If no such number is specified, a provider-specific default is used. (See the JDK Providers Documentation for the JDK Providers default values.) Thus, block ciphers can be turned into byte-oriented stream ciphers by using an 8 bit mode such as CFB8 or OFB8.

Modes such as Authenticated Encryption with Associated Data (AEAD) provide authenticity assurances for both confidential data and Additional Associated Data (AAD) that is not encrypted. (Please see RFC 5116 for more information on AEAD and AAD algorithms such as GCM/CCM.) Both confidential and AAD data can be used when calculating the authentication tag (similar to a Mac). This tag is appended to the ciphertext during encryption, and is verified on decryption.

AEAD modes such as GCM/CCM perform all AAD authenticity calculations before starting the ciphertext authenticity calculations. To avoid implementations having to internally buffer ciphertext, all AAD data must be supplied to GCM/CCM implementations (via the updateAAD methods) before the ciphertext is processed (via the update and doFinal methods).

Note that GCM mode has a uniqueness requirement on IVs used in encryption with a given key. When IVs are repeated for GCM encryption, such usages are subject to forgery attacks. Thus, after each encryption operation using GCM mode, callers should re-initialize the Cipher objects with GCM parameters which have a different IV value.

     GCMParameterSpec s = ...;
     cipher.init(..., s);

     // If the GCM parameters were generated by the provider, it can
     // be retrieved by:
     // cipher.getParameters().getParameterSpec(GCMParameterSpec.class);

     cipher.updateAAD(...);  // AAD
     cipher.update(...);     // Multi-part update
     cipher.doFinal(...);    // conclusion of operation

     // Use a different IV value for every encryption
     byte[] newIv = ...;
     s = new GCMParameterSpec(s.getTLen(), newIv);
     cipher.init(..., s);
     ...
The ChaCha20 and ChaCha20-Poly1305 algorithms have a similar requirement for unique nonces with a given key. After each encryption or decryption operation, callers should re-initialize their ChaCha20 or ChaCha20-Poly1305 ciphers with parameters that specify a different nonce value. Please see RFC 7539 for more information on the ChaCha20 and ChaCha20-Poly1305 algorithms.

Every implementation of the Java platform is required to support the following standard Cipher object transformations with the keysizes in parentheses:

  • AES/CBC/NoPadding (128)
  • AES/CBC/PKCS5Padding (128)
  • AES/ECB/NoPadding (128)
  • AES/ECB/PKCS5Padding (128)
  • AES/GCM/NoPadding (128)
  • DESede/CBC/NoPadding (168)
  • DESede/CBC/PKCS5Padding (168)
  • DESede/ECB/NoPadding (168)
  • DESede/ECB/PKCS5Padding (168)
  • RSA/ECB/PKCS1Padding (1024, 2048)
  • RSA/ECB/OAEPWithSHA-1AndMGF1Padding (1024, 2048)
  • RSA/ECB/OAEPWithSHA-256AndMGF1Padding (1024, 2048)
These transformations are described in the Cipher section of the Java Security Standard Algorithm Names Specification. Consult the release documentation for your implementation to see if any other transformations are supported.
Since:
1.4
See Also:

Field Summary

Modifier and Type Field Description
static final int DECRYPT_MODE
Constant used to initialize cipher to decryption mode.
static final int ENCRYPT_MODE
Constant used to initialize cipher to encryption mode.
static final int PRIVATE_KEY
Constant used to indicate the to-be-unwrapped key is a "private key".
static final int PUBLIC_KEY
Constant used to indicate the to-be-unwrapped key is a "public key".
static final int SECRET_KEY
Constant used to indicate the to-be-unwrapped key is a "secret key".
static final int UNWRAP_MODE
Constant used to initialize cipher to key-unwrapping mode.
static final int WRAP_MODE
Constant used to initialize cipher to key-wrapping mode.

Constructor Summary

Cipher(CipherSpi cipherSpi, Provider provider, String transformation)
Modifier Constructor Description
protected
Creates a Cipher object.

Method Summary

Modifier and Type Method Description
final byte[] doFinal()
Finishes a multiple-part encryption or decryption operation, depending on how this Cipher object was initialized.
final byte[] doFinal(byte[] input)
Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
final int doFinal(byte[] output, int outputOffset)
Finishes a multiple-part encryption or decryption operation, depending on how this Cipher object was initialized.
final byte[] doFinal(byte[] input, int inputOffset, int inputLen)
Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
final int doFinal(byte[] input, int inputOffset, int inputLen, byte[] output)
Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
final int doFinal(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.
final int doFinal(ByteBuffer input, ByteBuffer output)
Encrypts or decrypts data in a single-part operation, or finishes a multiple-part operation.
final String getAlgorithm()
Returns the algorithm name of this Cipher object.
final int getBlockSize()
Returns the block size (in bytes).
final ExemptionMechanism getExemptionMechanism()
Returns the exemption mechanism object used with this Cipher object.
static final Cipher getInstance(String transformation)
Returns a Cipher object that implements the specified transformation.
static final Cipher getInstance(String transformation, String provider)
Returns a Cipher object that implements the specified transformation.
static final Cipher getInstance(String transformation, Provider provider)
Returns a Cipher object that implements the specified transformation.
final byte[] getIV()
Returns the initialization vector (IV) in a new buffer.
static final int getMaxAllowedKeyLength(String transformation)
Returns the maximum key length for the specified transformation according to the installed JCE jurisdiction policy files.
static final AlgorithmParameterSpec getMaxAllowedParameterSpec(String transformation)
Returns an {code AlgorithmParameterSpec} object which contains the maximum Cipher parameter value according to the jurisdiction policy file.
final int getOutputSize(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).
final AlgorithmParameters getParameters()
Returns the parameters used with this Cipher object.
final Provider getProvider()
Returns the provider of this Cipher object.
final void init(int opmode, Certificate certificate)
Initializes this Cipher object with the public key from the given certificate.
final void init(int opmode, Certificate certificate, SecureRandom random)
Initializes this Cipher object with the public key from the given certificate and a source of randomness.
final void init(int opmode, Key key)
Initializes this Cipher object with a key.
final void init(int opmode, Key key, AlgorithmParameters params)
Initializes this Cipher object with a key and a set of algorithm parameters.
final void init(int opmode, Key key, AlgorithmParameters params, SecureRandom random)
Initializes this Cipher object with a key, a set of algorithm parameters, and a source of randomness.
final void init(int opmode, Key key, SecureRandom random)
Initializes this Cipher object with a key and a source of randomness.
final void init(int opmode, Key key, AlgorithmParameterSpec params)
Initializes this Cipher object with a key and a set of algorithm parameters.
final void init(int opmode, Key key, AlgorithmParameterSpec params, SecureRandom random)
Initializes this Cipher object with a key, a set of algorithm parameters, and a source of randomness.
String toString()
Returns a String representation of this Cipher object.
final Key unwrap(byte[] wrappedKey, String wrappedKeyAlgorithm, int wrappedKeyType)
Unwrap a previously wrapped key.
final byte[] update(byte[] input)
Continues a multiple-part encryption or decryption operation (depending on how this Cipher object was initialized), processing another data part.
final byte[] update(byte[] input, int inputOffset, int inputLen)
Continues a multiple-part encryption or decryption operation (depending on how this Cipher object was initialized), processing another data part.
final int update(byte[] input, int inputOffset, int inputLen, byte[] output)
Continues a multiple-part encryption or decryption operation (depending on how this Cipher object was initialized), processing another data part.
final int update(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset)
Continues a multiple-part encryption or decryption operation (depending on how this Cipher object was initialized), processing another data part.
final int update(ByteBuffer input, ByteBuffer output)
Continues a multiple-part encryption or decryption operation (depending on how this Cipher object was initialized), processing another data part.
final void updateAAD(byte[] src)
Continues a multi-part update of the Additional Authentication Data (AAD).
final void updateAAD(byte[] src, int offset, int len)
Continues a multi-part update of the Additional Authentication Data (AAD), using a subset of the provided buffer.
final void updateAAD(ByteBuffer src)
Continues a multi-part update of the Additional Authentication Data (AAD).
final byte[] wrap(Key key)
Wrap a key.

Methods declared in class java.lang.Object

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

Field Details

ENCRYPT_MODE

public static final int ENCRYPT_MODE
Constant used to initialize cipher to encryption mode.
See Also:

DECRYPT_MODE

public static final int DECRYPT_MODE
Constant used to initialize cipher to decryption mode.
See Also:

WRAP_MODE

public static final int WRAP_MODE
Constant used to initialize cipher to key-wrapping mode.
See Also:

UNWRAP_MODE

public static final int UNWRAP_MODE
Constant used to initialize cipher to key-unwrapping mode.
See Also:

PUBLIC_KEY

public static final int PUBLIC_KEY
Constant used to indicate the to-be-unwrapped key is a "public key".
See Also:

PRIVATE_KEY

public static final int PRIVATE_KEY
Constant used to indicate the to-be-unwrapped key is a "private key".
See Also:

SECRET_KEY

public static final int SECRET_KEY
Constant used to indicate the to-be-unwrapped key is a "secret key".
See Also:

Constructor Details

Cipher

protected Cipher(CipherSpi cipherSpi, Provider provider, String transformation)
Creates a Cipher object.
Parameters:
cipherSpi - the delegate
provider - the provider
transformation - the transformation
Throws:
NullPointerException - if provider is null
IllegalArgumentException - if the supplied arguments are deemed invalid for constructing the Cipher object

Method Details

getInstance

public static final Cipher getInstance(String transformation) throws NoSuchAlgorithmException, NoSuchPaddingException
Returns a Cipher object that implements the specified transformation.

This method traverses the list of registered security providers, starting with the most preferred provider. A new Cipher object encapsulating the CipherSpi implementation from the first provider that supports the specified algorithm is returned.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

API Note:
It is recommended to use a transformation that fully specifies the algorithm, mode, and padding. By not doing so, the provider will use a default for the mode and padding which may not meet the security requirements of your application.
Implementation Note:
The JDK Reference Implementation additionally uses the jdk.security.provider.preferred Security property to determine the preferred provider order for the specified algorithm. This may be different than the order of providers returned by Security.getProviders(). See also the Cipher Transformations section of the JDK Providers document for information on the transformation defaults used by JDK providers.
Parameters:
transformation - the name of the transformation, e.g., AES/CBC/PKCS5Padding. See the Cipher section in the Java Security Standard Algorithm Names Specification for information about standard transformation names.
Returns:
a Cipher object that implements the requested transformation
Throws:
NoSuchAlgorithmException - if transformation is null, empty, in an invalid format, or if no provider supports a CipherSpi implementation for the specified algorithm
NoSuchPaddingException - if transformation contains a padding scheme that is not available
See Also:

getInstance

public static final Cipher getInstance(String transformation, String provider) throws NoSuchAlgorithmException, NoSuchProviderException, NoSuchPaddingException
Returns a Cipher object that implements the specified transformation.

A new Cipher object encapsulating the CipherSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

Note that the list of registered providers may be retrieved via the Security.getProviders() method.

API Note:
It is recommended to use a transformation that fully specifies the algorithm, mode, and padding. By not doing so, the provider will use a default for the mode and padding which may not meet the security requirements of your application.
Implementation Note:
See the Cipher Transformations section of the JDK Providers document for information on the transformation defaults used by JDK providers.
Parameters:
transformation - the name of the transformation, e.g., AES/CBC/PKCS5Padding. See the Cipher section in the Java Security Standard Algorithm Names Specification for information about standard transformation names.
provider - the name of the provider
Returns:
a Cipher object that implements the requested transformation
Throws:
IllegalArgumentException - if the provider is null or empty
NoSuchAlgorithmException - if transformation is null, empty, in an invalid format, or if a CipherSpi implementation for the specified algorithm is not available from the specified provider
NoSuchPaddingException - if transformation contains a padding scheme that is not available
NoSuchProviderException - if the specified provider is not registered in the security provider list
See Also:

getInstance

public static final Cipher getInstance(String transformation, Provider provider) throws NoSuchAlgorithmException, NoSuchPaddingException
Returns a Cipher object that implements the specified transformation.

A new Cipher object encapsulating the CipherSpi implementation from the specified provider object is returned. Note that the specified provider object does not have to be registered in the provider list.

API Note:
It is recommended to use a transformation that fully specifies the algorithm, mode, and padding. By not doing so, the provider will use a default for the mode and padding which may not meet the security requirements of your application.
Implementation Note:
See the Cipher Transformations section of the JDK Providers document for information on the transformation defaults used by JDK providers.
Parameters:
transformation - the name of the transformation, e.g., AES/CBC/PKCS5Padding. See the Cipher section in the Java Security Standard Algorithm Names Specification for information about standard transformation names.
provider - the provider
Returns:
a Cipher object that implements the requested transformation
Throws:
IllegalArgumentException - if the provider is null
NoSuchAlgorithmException - if transformation is null, empty, in an invalid format, or if a CipherSpi implementation for the specified algorithm is not available from the specified provider object
NoSuchPaddingException - if transformation contains a padding scheme that is not available
See Also:

getProvider

public final Provider getProvider()
Returns the provider of this Cipher object.
Returns:
the provider of this Cipher object

getAlgorithm

public final String getAlgorithm()
Returns the algorithm name of this Cipher object.

This is the same name that was specified in one of the getInstance calls that created this Cipher object.

Returns:
the algorithm name of this Cipher object

getBlockSize

public final int getBlockSize()
Returns the block size (in bytes).
Returns:
the block size (in bytes), or 0 if this cipher is not a block cipher

getOutputSize

public final int getOutputSize(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.

Parameters:
inputLen - the input length (in bytes)
Returns:
the required output buffer size (in bytes)
Throws:
IllegalStateException - if this Cipher object is in a wrong state (e.g., has not yet been initialized)

getIV

public final byte[] getIV()
Returns the initialization vector (IV) in a new buffer.

This is useful in the case where a random IV was created, or in the context of password-based encryption or decryption, where the IV is derived from a user-supplied password.

Returns:
the initialization vector in a new buffer, or null if this cipher does not use an IV, or if the IV has not yet been set.

getParameters

public final AlgorithmParameters getParameters()
Returns the parameters used with this Cipher object.

The returned parameters may be the same that were used to initialize this cipher, or may contain additional default or random parameter values used by the underlying cipher implementation. If the required parameters were not supplied and can be generated by the cipher, the generated parameters are returned. Otherwise, null is returned.

Returns:
the parameters used with this cipher, or null

getExemptionMechanism

public final ExemptionMechanism getExemptionMechanism()
Returns the exemption mechanism object used with this Cipher object.
Returns:
the exemption mechanism object used with this Cipher object, or null if this Cipher object does not use any exemption mechanism.

init

public final void init(int opmode, Key key) throws InvalidKeyException
Initializes this Cipher object with a key.

The Cipher object 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 getParameters or getIV (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 feedback or padding scheme) requires any random bytes (e.g., for parameter generation), it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

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

Parameters:
opmode - the operation mode of this Cipher object (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key - the key
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher, or requires algorithm parameters that cannot be determined from the given key, or if the given key has a keysize that exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files)
UnsupportedOperationException - if opmode is WRAP_MODE or UNWRAP_MODE but the mode is not implemented by the underlying CipherSpi
InvalidParameterException - if opmode is not one of the recognized values

init

public final void init(int opmode, Key key, SecureRandom random) throws InvalidKeyException
Initializes this Cipher object with a key and a source of randomness.

The Cipher object 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 getParameters or getIV (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 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 object is equivalent to creating a new instance of that Cipher object and initializing it.

Parameters:
opmode - the operation mode of this Cipher object (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key - the encryption key
random - the source of randomness
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher, or requires algorithm parameters that cannot be determined from the given key, or if the given key has a keysize that exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files)
UnsupportedOperationException - if opmode is WRAP_MODE or UNWRAP_MODE but the mode is not implemented by the underlying CipherSpi
InvalidParameterException - if opmode is not one of the recognized values

init

public final void init(int opmode, Key key, AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException
Initializes this Cipher object with a key and a set of algorithm parameters.

The Cipher object 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 getParameters or getIV (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 feedback or padding scheme) requires any random bytes (e.g., for parameter generation), it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

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

Parameters:
opmode - the operation mode of this Cipher object (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key - the encryption key
params - the algorithm parameters
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher, or its keysize exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files)
InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this cipher, or this cipher requires algorithm parameters and params is null, or the given algorithm parameters imply a cryptographic strength that would exceed the legal limits (as determined from the configured jurisdiction policy files)
UnsupportedOperationException - if opmode is WRAP_MODE or UNWRAP_MODE but the mode is not implemented by the underlying CipherSpi
InvalidParameterException - if opmode is not one of the recognized values

init

public final void init(int opmode, Key key, AlgorithmParameterSpec params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
Initializes this Cipher object with a key, a set of algorithm parameters, and a source of randomness.

The Cipher object 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 getParameters or getIV (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 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 object is equivalent to creating a new instance of that Cipher object and initializing it.

Parameters:
opmode - the operation mode of this Cipher object (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key - the encryption key
params - the algorithm parameters
random - the source of randomness
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher, or its keysize exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files)
InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this cipher, or this cipher requires algorithm parameters and params is null, or the given algorithm parameters imply a cryptographic strength that would exceed the legal limits (as determined from the configured jurisdiction policy files)
UnsupportedOperationException - if opmode is WRAP_MODE or UNWRAP_MODE but the mode is not implemented by the underlying CipherSpi
InvalidParameterException - if opmode is not one of the recognized values

init

public final void init(int opmode, Key key, AlgorithmParameters params) throws InvalidKeyException, InvalidAlgorithmParameterException
Initializes this Cipher object with a key and a set of algorithm parameters.

The Cipher object 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 getParameters or getIV (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 feedback or padding scheme) requires any random bytes (e.g., for parameter generation), it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

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

Parameters:
opmode - the operation mode of this Cipher object this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key - the encryption key
params - the algorithm parameters
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher, or its keysize exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files).
InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this cipher, or this cipher requires algorithm parameters and params is null, or the given algorithm parameters imply a cryptographic strength that would exceed the legal limits (as determined from the configured jurisdiction policy files)
UnsupportedOperationException - if opmode is WRAP_MODE or UNWRAP_MODE but the mode is not implemented by the underlying CipherSpi
InvalidParameterException - if opmode is not one of the recognized values

init

public final void init(int opmode, Key key, AlgorithmParameters params, SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException
Initializes this Cipher object with a key, a set of algorithm parameters, and a source of randomness.

The Cipher object 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 getParameters or getIV (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 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 object is equivalent to creating a new instance of that Cipher object and initializing it.

Parameters:
opmode - the operation mode of this Cipher object (this is one of the following: ENCRYPT_MODE, DECRYPT_MODE, WRAP_MODE or UNWRAP_MODE)
key - the encryption key
params - the algorithm parameters
random - the source of randomness
Throws:
InvalidKeyException - if the given key is inappropriate for initializing this cipher, or its keysize exceeds the maximum allowable keysize (as determined from the configured jurisdiction policy files)
InvalidAlgorithmParameterException - if the given algorithm parameters are inappropriate for this cipher, or this cipher requires algorithm parameters and params is null, or the given algorithm parameters imply a cryptographic strength that would exceed the legal limits (as determined from the configured jurisdiction policy files)
UnsupportedOperationException - if opmode is WRAP_MODE or UNWRAP_MODE but the mode is not implemented by the underlying CipherSpi