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package com.sun.crypto.provider;
import java.security.InvalidKeyException;
import java.security.ProviderException;
This class represents ciphers in Plaintext Cipher Block Chaining (PCBC)
mode.
This mode is implemented independently of a particular cipher.
Ciphers to which this mode should apply (e.g., DES) must be
plugged-in using the constructor.
NOTE: This class does not deal with buffering or padding.
Author: Gigi Ankeny
/**
* This class represents ciphers in Plaintext Cipher Block Chaining (PCBC)
* 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 PCBC extends FeedbackCipher {
/*
* output buffer
*/
private final byte[] k;
// variables for save/restore calls
private byte[] kSave = null;
PCBC(SymmetricCipher embeddedCipher) {
super(embeddedCipher);
k = new byte[blockSize];
}
Gets the name of this feedback mode.
Returns: the string PCBC
/**
* Gets the name of this feedback mode.
*
* @return the string <code>PCBC</code>
*/
String getFeedback() {
return "PCBC";
}
Initializes the cipher in the specified mode with the given key
and iv.
Params: - decrypting – flag indicating encryption or decryption
- algorithm – the algorithm name
- key – the key
- iv – the iv
Throws: - InvalidKeyException – if the given key is inappropriate for
initializing this cipher
/**
* 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();
embeddedCipher.init(decrypting, 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).
/**
* 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, k, 0, blockSize);
}
Save the current content of this cipher.
/**
* Save the current content of this cipher.
*/
void save() {
if (kSave == null) {
kSave = new byte[blockSize];
}
System.arraycopy(k, 0, kSave, 0, blockSize);
}
Restores the content of this cipher to the previous saved one.
/**
* Restores the content of this cipher to the previous saved one.
*/
void restore() {
System.arraycopy(kSave, 0, k, 0, blockSize);
}
Performs encryption operation.
The input plain text plain, starting at
plainOffset and ending at
(plainOffset + plainLen - 1), is encrypted.
The result is stored in cipher, starting at
cipherOffset.
Params: - plain – the buffer with the input data to be encrypted
- plainOffset – the offset in
plain - plainLen – the length of the input data
- cipher – the buffer for the result
- cipherOffset – the offset in
cipher
Throws: - ProviderException – if
plainLen is not
a multiple of the block size
Returns: the length of the encrypted data
/**
* 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 block size
* @return the length of the encrypted data
*/
int encrypt(byte[] plain, int plainOffset, int plainLen,
byte[] cipher, int cipherOffset)
{
RangeUtil.blockSizeCheck(plainLen, blockSize);
RangeUtil.nullAndBoundsCheck(plain, plainOffset, plainLen);
RangeUtil.nullAndBoundsCheck(cipher, cipherOffset, plainLen);
int i;
int endIndex = plainOffset + plainLen;
for (; plainOffset < endIndex;
plainOffset += blockSize, cipherOffset += blockSize) {
for (i = 0; i < blockSize; i++) {
k[i] ^= plain[i + plainOffset];
}
embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);
for (i = 0; i < blockSize; i++) {
k[i] = (byte)(plain[i + plainOffset] ^ cipher[i + cipherOffset]);
}
}
return plainLen;
}
Performs decryption operation.
The input cipher text cipher, starting at
cipherOffset and ending at
(cipherOffset + cipherLen - 1), is decrypted.
The result is stored in plain, starting at
plainOffset.
Params: - cipher – the buffer with the input data to be decrypted
- cipherOffset – the offset in
cipherOffset - cipherLen – the length of the input data
- plain – the buffer for the result
- plainOffset – the offset in
plain
Throws: - ProviderException – if
cipherLen is not
a multiple of the block size
Returns: the length of the decrypted data
/**
* Performs decryption operation.
*
* <p>The input cipher text <code>cipher</code>, starting at
* <code>cipherOffset</code> and ending at
* <code>(cipherOffset + cipherLen - 1)</code>, is decrypted.
* The result is stored in <code>plain</code>, starting at
* <code>plainOffset</code>.
*
* @param cipher the buffer with the input data to be decrypted
* @param cipherOffset the offset in <code>cipherOffset</code>
* @param cipherLen the length of the input data
* @param plain the buffer for the result
* @param plainOffset the offset in <code>plain</code>
* @exception ProviderException if <code>cipherLen</code> is not
* a multiple of the block size
* @return the length of the decrypted data
*/
int decrypt(byte[] cipher, int cipherOffset, int cipherLen,
byte[] plain, int plainOffset)
{
RangeUtil.blockSizeCheck(cipherLen, blockSize);
RangeUtil.nullAndBoundsCheck(cipher, cipherOffset, cipherLen);
RangeUtil.nullAndBoundsCheck(plain, plainOffset, cipherLen);
int i;
int endIndex = cipherOffset + cipherLen;
for (; cipherOffset < endIndex;
plainOffset += blockSize, cipherOffset += blockSize) {
embeddedCipher.decryptBlock(cipher, cipherOffset,
plain, plainOffset);
for (i = 0; i < blockSize; i++) {
plain[i + plainOffset] ^= k[i];
}
for (i = 0; i < blockSize; i++) {
k[i] = (byte)(plain[i + plainOffset] ^ cipher[i + cipherOffset]);
}
}
return cipherLen;
}
}