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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package com.sun.crypto.provider;
import java.security.InvalidKeyException;
import java.security.ProviderException;
/**
* This class represents ciphers in output-feedback (OFB) mode.
*
* <p>This mode is implemented independently of a particular cipher.
* Ciphers to which this mode should apply (e.g., DES) must be
* <i>plugged-in</i> using the constructor.
*
* <p>NOTE: This class does not deal with buffering or padding.
*
* @author Gigi Ankeny
*/
final class OutputFeedback extends FeedbackCipher {
/*
* output buffer
*/
private byte[] k = null;
/*
* register buffer
*/
private byte[] register = null;
/*
* number of bytes for each stream unit, defaults to the blocksize
* of the embedded cipher
*/
private int numBytes;
// variables for save/restore calls
private byte[] registerSave = null;
OutputFeedback(SymmetricCipher embeddedCipher, int numBytes) {
super(embeddedCipher);
if (numBytes > blockSize) {
numBytes = blockSize;
}
this.numBytes = numBytes;
k = new byte[blockSize];
register = new byte[blockSize];
}
/**
* Gets the name of this feedback mode.
*
* @return the string <code>OFB</code>
*/
String getFeedback() {
return "OFB";
}
/**
* Initializes the cipher in the specified mode with the given key
* and iv.
*
* @param decrypting flag indicating encryption or decryption
* @param algorithm the algorithm name
* @param key the key
* @param iv the iv
*
* @exception InvalidKeyException if the given key is inappropriate for
* initializing this cipher
*/
void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
throws InvalidKeyException {
if ((key == null) || (iv == null) || (iv.length != blockSize)) {
throw new InvalidKeyException("Internal error");
}
this.iv = iv;
reset();
// always encrypt mode for embedded cipher
embeddedCipher.init(false, algorithm, key);
}
/**
* Resets the iv to its original value.
* This is used when doFinal is called in the Cipher class, so that the
* cipher can be reused (with its original iv).
*/
void reset() {
System.arraycopy(iv, 0, register, 0, blockSize);
}
/**
* Save the current content of this cipher.
*/
void save() {
if (registerSave == null) {
registerSave = new byte[blockSize];
}
System.arraycopy(register, 0, registerSave, 0, blockSize);
}
/**
* Restores the content of this cipher to the previous saved one.
*/
void restore() {
System.arraycopy(registerSave, 0, register, 0, blockSize);
}
/**
* Performs encryption operation.
*
* <p>The input plain text <code>plain</code>, starting at
* <code>plainOffset</code> and ending at
* <code>(plainOffset + plainLen - 1)</code>, is encrypted.
* The result is stored in <code>cipher</code>, starting at
* <code>cipherOffset</code>.
*
* @param plain the buffer with the input data to be encrypted
* @param plainOffset the offset in <code>plain</code>
* @param plainLen the length of the input data
* @param cipher the buffer for the result
* @param cipherOffset the offset in <code>cipher</code>
* @exception ProviderException if <code>plainLen</code> is not
* a multiple of the <code>numBytes</code>
* @return the length of the encrypted data
*/
int encrypt(byte[] plain, int plainOffset, int plainLen,
byte[] cipher, int cipherOffset) {
if ((plainLen % numBytes) != 0) {
throw new ProviderException("Internal error in input buffering");
}
int nShift = blockSize - numBytes;
int loopCount = plainLen / numBytes;
for (; loopCount > 0;
plainOffset += numBytes, cipherOffset += numBytes,
loopCount--) {
embeddedCipher.encryptBlock(register, 0, k, 0);
for (int i = 0; i < numBytes; i++) {
cipher[i + cipherOffset] =
(byte)(k[i] ^ plain[i + plainOffset]);
if (nShift != 0) {
System.arraycopy(register, numBytes, register, 0, nShift);
}
System.arraycopy(k, 0, register, nShift, numBytes);
}
}
return plainLen;
}
/**
* Performs last encryption operation.
*
* <p>The input plain text <code>plain</code>, starting at
* <code>plainOffset</code> and ending at
* <code>(plainOffset + plainLen - 1)</code>, is encrypted.
* The result is stored in <code>cipher</code>, starting at
* <code>cipherOffset</code>.
*
* @param plain the buffer with the input data to be encrypted
* @param plainOffset the offset in <code>plain</code>
* @param plainLen the length of the input data
* @param cipher the buffer for the result
* @param cipherOffset the offset in <code>cipher</code>
* @return the length of the encrypted data
*/
int encryptFinal(byte[] plain, int plainOffset, int plainLen,
byte[] cipher, int cipherOffset) {
int oddBytes = plainLen % numBytes;
int len = encrypt(plain, plainOffset, (plainLen - oddBytes),
cipher, cipherOffset);
plainOffset += len;
cipherOffset += len;
if (oddBytes != 0) {
embeddedCipher.encryptBlock(register, 0, k, 0);
for (int i = 0; i < oddBytes; i++) {
cipher[i + cipherOffset] =
(byte)(k[i] ^ plain[ i + plainOffset]);
}
}
return plainLen;
}
// OFB encrypt and decrypt are identical
int decrypt(byte[] cipher, int cipherOffset, int cipherLen,
byte[] plain, int plainOffset) {
return encrypt(cipher, cipherOffset, cipherLen, plain, plainOffset);
}
// OFB encrypt and decrypt are identical
int decryptFinal(byte[] cipher, int cipherOffset, int cipherLen,
byte[] plain, int plainOffset) {
// OFB encrypt and decrypt are identical
return encryptFinal(cipher, cipherOffset, cipherLen, plain, plainOffset);
}
}