GCMParameterSpec

public class GCMParameterSpec
extends Object implements AlgorithmParameterSpec

java.lang.Object
↳	javax.crypto.spec.GCMParameterSpec

Specifies the set of parameters required by a Cipher using the Galois/Counter Mode (GCM) mode.

Simple block cipher modes (such as CBC) generally require only an initialization vector (such as IvParameterSpec), but GCM needs these parameters:

IV: Initialization Vector (IV)
tLen: length (in bits) of authentication tag T

In addition to the parameters described here, other GCM inputs/output (Additional Authenticated Data (AAD), Keys, block ciphers, plain/ciphertext and authentication tags) are handled in the Cipher class.

Please see RFC 5116 for more information on the Authenticated Encryption with Associated Data (AEAD) algorithm, and NIST Special Publication 800-38D, "NIST Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC."

The GCM specification states that tLen may only have the values {128, 120, 112, 104, 96}, or {64, 32} for certain applications. Other values can be specified for this class, but not all CSP implementations will support them.

See also:

Cipher

Summary

Public constructors
`GCMParameterSpec(int tLen, byte[] src)` Constructs a GCMParameterSpec using the specified authentication tag bit-length and IV buffer.
`GCMParameterSpec(int tLen, byte[] src, int offset, int len)` Constructs a GCMParameterSpec object using the specified authentication tag bit-length and a subset of the specified buffer as the IV.

Public methods
`byte[]`	`getIV()` Returns the Initialization Vector (IV).
`int`	`getTLen()` Returns the authentication tag length.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(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`	`wait(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`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public constructors

GCMParameterSpec

Added in API level 19

public GCMParameterSpec (int tLen, 
                byte[] src)

Constructs a GCMParameterSpec using the specified authentication tag bit-length and IV buffer.

Parameters
`tLen`	`int`: the authentication tag length (in bits)
`src`	`byte`: the IV source buffer. The contents of the buffer are copied to protect against subsequent modification.

Throws
`IllegalArgumentException`	if `tLen` is negative, or `src` is null.

GCMParameterSpec

Added in API level 19

public GCMParameterSpec (int tLen, 
                byte[] src, 
                int offset, 
                int len)

Constructs a GCMParameterSpec object using the specified authentication tag bit-length and a subset of the specified buffer as the IV.

Parameters
`tLen`	`int`: the authentication tag length (in bits)
`src`	`byte`: the IV source buffer. The contents of the buffer are copied to protect against subsequent modification.
`offset`	`int`: the offset in `src` where the IV starts
`len`	`int`: the number of IV bytes

Throws
`IllegalArgumentException`	if `tLen` is negative, `src` is null, `len` or `offset` is negative, or the sum of `offset` and `len` is greater than the length of the `src` byte array.

Public methods

getIV

Added in API level 19

public byte[] getIV ()

Returns the Initialization Vector (IV).

Returns
`byte[]`	the IV. Creates a new array each time this method is called.

getTLen

Added in API level 19

public int getTLen ()

Returns the authentication tag length.

Returns
`int`	the authentication tag length (in bits)