Package org.bouncycastle.crypto.macs
Class GMac
- java.lang.Object
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- org.bouncycastle.crypto.macs.GMac
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- All Implemented Interfaces:
Mac
public class GMac extends java.lang.Object implements Mac
The GMAC specialisation of Galois/Counter mode (GCM) detailed in NIST Special Publication 800-38D.GMac is an invocation of the GCM mode where no data is encrypted (i.e. all input data to the Mac is processed as additional authenticated data with the underlying GCM block cipher).
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Constructor Summary
Constructors Constructor Description GMac(GCMBlockCipher cipher)
Creates a GMAC based on the operation of a block cipher in GCM mode.GMac(GCMBlockCipher cipher, int macSizeBits)
Creates a GMAC based on the operation of a 128 bit block cipher in GCM mode.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description int
doFinal(byte[] out, int outOff)
Compute the final stage of the MAC writing the output to the out parameter.java.lang.String
getAlgorithmName()
Return the name of the algorithm the MAC implements.int
getMacSize()
Return the block size for this MAC (in bytes).void
init(CipherParameters params)
Initialises the GMAC - requires aParametersWithIV
providing aKeyParameter
and a nonce.void
reset()
Reset the MAC.void
update(byte in)
add a single byte to the mac for processing.void
update(byte[] in, int inOff, int len)
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Constructor Detail
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GMac
public GMac(GCMBlockCipher cipher)
Creates a GMAC based on the operation of a block cipher in GCM mode.This will produce an authentication code the length of the block size of the cipher.
- Parameters:
cipher
- the cipher to be used in GCM mode to generate the MAC.
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GMac
public GMac(GCMBlockCipher cipher, int macSizeBits)
Creates a GMAC based on the operation of a 128 bit block cipher in GCM mode.- Parameters:
macSizeBits
- the mac size to generate, in bits. Must be a multiple of 8 and >= 32 and <= 128. Sizes less than 96 are not recommended, but are supported for specialized applications.cipher
- the cipher to be used in GCM mode to generate the MAC.
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Method Detail
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init
public void init(CipherParameters params) throws java.lang.IllegalArgumentException
Initialises the GMAC - requires aParametersWithIV
providing aKeyParameter
and a nonce.
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getAlgorithmName
public java.lang.String getAlgorithmName()
Description copied from interface:Mac
Return the name of the algorithm the MAC implements.- Specified by:
getAlgorithmName
in interfaceMac
- Returns:
- the name of the algorithm the MAC implements.
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getMacSize
public int getMacSize()
Description copied from interface:Mac
Return the block size for this MAC (in bytes).- Specified by:
getMacSize
in interfaceMac
- Returns:
- the block size for this MAC in bytes.
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update
public void update(byte in) throws java.lang.IllegalStateException
Description copied from interface:Mac
add a single byte to the mac for processing.
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update
public void update(byte[] in, int inOff, int len) throws DataLengthException, java.lang.IllegalStateException
- Specified by:
update
in interfaceMac
- Parameters:
in
- the array containing the input.inOff
- the index in the array the data begins at.len
- the length of the input starting at inOff.- Throws:
DataLengthException
- if there isn't enough data in in.java.lang.IllegalStateException
- if the MAC is not initialised.
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doFinal
public int doFinal(byte[] out, int outOff) throws DataLengthException, java.lang.IllegalStateException
Description copied from interface:Mac
Compute the final stage of the MAC writing the output to the out parameter.doFinal leaves the MAC in the same state it was after the last init.
- Specified by:
doFinal
in interfaceMac
- Parameters:
out
- the array the MAC is to be output to.outOff
- the offset into the out buffer the output is to start at.- Throws:
DataLengthException
- if there isn't enough space in out.java.lang.IllegalStateException
- if the MAC is not initialised.
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