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package com.sun.crypto.provider;

import java.security.InvalidKeyException;
import java.security.ProviderException;

This class represents ciphers in cipher-feedback (CFB) 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 cipher-feedback (CFB) 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 CipherFeedback extends FeedbackCipher { /* * encrypt/decrypt output buffer */ private final byte[] k; /* * register value, initialized with iv */ private final byte[] register; /* * 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; CipherFeedback(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.
Returns:the string CFB
/** * Gets the name of this feedback mode. * * @return the string <code>CFB</code> */
String getFeedback() { return "CFB"; }
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:
/** * 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).
/** * 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.
/** * 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.
/** * Restores the content of this cipher to the previous saved one. */
void restore() { System.arraycopy(registerSave, 0, register, 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:
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 <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); if (nShift != 0) { System.arraycopy(register, numBytes, register, 0, nShift); } for (int i = 0; i < numBytes; i++) { register[nShift + i] = cipher[i + cipherOffset] = (byte)(k[i] ^ plain[i + plainOffset]); } } return plainLen; }
Performs the last 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
Returns:the number of bytes placed into cipher
/** * Performs the 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 number of bytes placed into <code>cipher</code> */
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; }
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:
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 <code>numBytes</code> * @return the length of the decrypted data */
int decrypt(byte[] cipher, int cipherOffset, int cipherLen, byte[] plain, int plainOffset) { if ((cipherLen % numBytes) != 0) { throw new ProviderException("Internal error in input buffering"); } int nShift = blockSize - numBytes; int loopCount = cipherLen / numBytes; for (; loopCount > 0; plainOffset += numBytes, cipherOffset += numBytes, loopCount--) { embeddedCipher.encryptBlock(register, 0, k, 0); if (nShift != 0) { System.arraycopy(register, numBytes, register, 0, nShift); } for (int i = 0; i < numBytes; i++) { register[i + nShift] = cipher[i + cipherOffset]; plain[i + plainOffset] = (byte)(cipher[i + cipherOffset] ^ k[i]); } } return cipherLen; }
Performs the last 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
Returns:the length of the decrypted data
/** * Performs the last 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> * @return the length of the decrypted data */
int decryptFinal(byte[] cipher, int cipherOffset, int cipherLen, byte[] plain, int plainOffset) { int oddBytes = cipherLen % numBytes; int len = decrypt(cipher, cipherOffset, (cipherLen - oddBytes), plain, plainOffset); cipherOffset += len; plainOffset += len; if (oddBytes != 0) { embeddedCipher.encryptBlock(register, 0, k, 0); for (int i = 0; i < oddBytes; i++) { plain[i + plainOffset] = (byte)(cipher[i + cipherOffset] ^ k[i]); } } return cipherLen; } }