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:

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

Public constructors

GCMParameterSpec

added in API level 19
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
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
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
int getTLen ()

Returns the authentication tag length.

Returns
int the authentication tag length (in bits)