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package javax.crypto.spec;
import java.security.spec.AlgorithmParameterSpec;
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: Since: 1.7
/**
* Specifies the set of parameters required by a {@link
* javax.crypto.Cipher} using the Galois/Counter Mode (GCM) mode.
* <p>
* Simple block cipher modes (such as CBC) generally require only an
* initialization vector (such as {@code IvParameterSpec}),
* but GCM needs these parameters:
* <ul>
* <li>{@code IV}: Initialization Vector (IV) </li>
* <li>{@code tLen}: length (in bits) of authentication tag T</li>
* </ul>
* <p>
* 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 {@code
* Cipher} class.
* <p>
* Please see <a href="http://www.ietf.org/rfc/rfc5116.txt"> RFC 5116
* </a> for more information on the Authenticated Encryption with
* Associated Data (AEAD) algorithm, and <a href=
* "http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf">
* NIST Special Publication 800-38D</a>, "NIST Recommendation for Block
* Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC."
* <p>
* The GCM specification states that {@code 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 javax.crypto.Cipher
*
* @since 1.7
*/
public class GCMParameterSpec implements AlgorithmParameterSpec {
// Initialization Vector. Could use IvParameterSpec, but that
// would add extra copies.
private byte[] iv;
// Required Tag length (in bits).
private int tLen;
Constructs a GCMParameterSpec using the specified authentication
tag bit-length and IV buffer.
Params: - tLen – the authentication tag length (in bits)
- src – 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.
/**
* Constructs a GCMParameterSpec using the specified authentication
* tag bit-length and IV buffer.
*
* @param tLen the authentication tag length (in bits)
* @param src the IV source buffer. The contents of the buffer are
* copied to protect against subsequent modification.
*
* @throws IllegalArgumentException if {@code tLen} is negative,
* or {@code src} is null.
*/
public GCMParameterSpec(int tLen, byte[] src) {
if (src == null) {
throw new IllegalArgumentException("src array is null");
}
init(tLen, src, 0, src.length);
}
Constructs a GCMParameterSpec object using the specified
authentication tag bit-length and a subset of the specified
buffer as the IV.
Params: - tLen – the authentication tag length (in bits)
- src – the IV source buffer. The contents of the
buffer are copied to protect against subsequent modification.
- offset – the offset in
src where the IV starts - len – 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.
/**
* Constructs a GCMParameterSpec object using the specified
* authentication tag bit-length and a subset of the specified
* buffer as the IV.
*
* @param tLen the authentication tag length (in bits)
* @param src the IV source buffer. The contents of the
* buffer are copied to protect against subsequent modification.
* @param offset the offset in {@code src} where the IV starts
* @param len the number of IV bytes
*
* @throws IllegalArgumentException if {@code tLen} is negative,
* {@code src} is null, {@code len} or {@code offset} is negative,
* or the sum of {@code offset} and {@code len} is greater than the
* length of the {@code src} byte array.
*/
public GCMParameterSpec(int tLen, byte[] src, int offset, int len) {
init(tLen, src, offset, len);
}
/*
* Check input parameters.
*/
private void init(int tLen, byte[] src, int offset, int len) {
if (tLen < 0) {
throw new IllegalArgumentException(
"Length argument is negative");
}
this.tLen = tLen;
// Input sanity check
if ((src == null) ||(len < 0) || (offset < 0)
|| (len > (src.length - offset))) {
throw new IllegalArgumentException("Invalid buffer arguments");
}
iv = new byte[len];
System.arraycopy(src, offset, iv, 0, len);
}
Returns the authentication tag length.
Returns: the authentication tag length (in bits)
/**
* Returns the authentication tag length.
*
* @return the authentication tag length (in bits)
*/
public int getTLen() {
return tLen;
}
Returns the Initialization Vector (IV).
Returns: the IV. Creates a new array each time this method
is called.
/**
* Returns the Initialization Vector (IV).
*
* @return the IV. Creates a new array each time this method
* is called.
*/
public byte[] getIV() {
return iv.clone();
}
}