gt:         for (int n = 0; n < blockSize; n++) 
context: package org.bouncycastle.crypto.modes;
  
  import org.bouncycastle.crypto.BlockCipher;
  import org.bouncycastle.crypto.CipherParameters;
  import org.bouncycastle.crypto.DataLengthException;
  import org.bouncycastle.crypto.params.ParametersWithIV;
  
  /**
   * Implements OpenPGP's rather strange version of Cipher-FeedBack (CFB) mode on top of a simple cipher. For further info see <a href="http://www.ietf.org/rfc/rfc2440.html">RFC 2440</a>.
   */
  public class PGPCFBBlockCipher
      implements BlockCipher
  {
      private byte[] IV;
      private byte[] FR;
      private byte[] FRE;
      private byte[] tmp;
  
      private BlockCipher cipher;
  
      private int count;
      private int blockSize;
      private boolean forEncryption;
      
      private boolean inlineIv; // if false we don't need to prepend an IV
  
      /**
       * Basic constructor.
       *
       * @param cipher the block cipher to be used as the basis of the
       * feedback mode.
       * @param inlineIv if true this is for PGP CFB with a prepended iv.
       */
      public PGPCFBBlockCipher(
          BlockCipher cipher,
          boolean     inlineIv)
      {
          this.cipher = cipher;
          this.inlineIv = inlineIv;
  
          this.blockSize = cipher.getBlockSize();
          this.IV = new byte[blockSize];
          this.FR = new byte[blockSize];
          this.FRE = new byte[blockSize];
          this.tmp = new byte[blockSize];
      }
  
      /**
       * return the underlying block cipher that we are wrapping.
       *
       * @return the underlying block cipher that we are wrapping.
       */
      public BlockCipher getUnderlyingCipher()
      {
          return cipher;
      }
      
      /**
       * return the algorithm name and mode.
       *
       * @return the name of the underlying algorithm followed by "/PGPCFB"
       * and the block size in bits.
       */
      public String getAlgorithmName()
      {
          if (inlineIv)
          {
              return cipher.getAlgorithmName() + "/PGPCFBwithIV";
          }
          else
          {
              return cipher.getAlgorithmName() + "/PGPCFB";
          }
      }
      
      /**
       * return the block size we are operating at.
       *
       * @return the block size we are operating at (in bytes).
       */
      public int getBlockSize()
      {
          return cipher.getBlockSize();
      }
  
      /**
       * Process one block of input from the array in and write it to
       * the out array.
       *
       * @param in the array containing the input data.
       * @param inOff offset into the in array the data starts at.
       * @param out the array the output data will be copied into.
       * @param outOff the offset into the out array the output will start at.
       * @exception DataLengthException if there isn't enough data in in, or
       * space in out.
       * @exception IllegalStateException if the cipher isn't initialised.
       * @return the number of bytes processed and produced.
       */
      public int processBlock(
          byte[] in,
          int inOff,
          byte[] out,
          int outOff)
          throws DataLengthException, IllegalStateException
      {
          if (inlineIv)
          {
              return (forEncryption) ? encryptBlockWithIV(in, inOff, out, outOff) : decryptBlockWithIV(in, inOff, out, outOff);
          }
          else
          {
              return (forEncryption) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff);
          }
      }
      
      /**
       * reset the chaining vector back to the IV and reset the underlying
       * cipher.
       */
      public void reset()
      {
          count = 0;
  
          for (int i = 0; i != FR.length; i++)
          {
              if (inlineIv)
              {
                  FR[i] = 0;
              }
              else
              {
                  FR[i] = IV[i]; // if simple mode, key is IV (even if this is zero)
              }
          }
  
          cipher.reset();
      }
  
      /**
       * Initialise the cipher and, possibly, the initialisation vector (IV).
       * If an IV isn't passed as part of the parameter, the IV will be all zeros.
       * An IV which is too short is handled in FIPS compliant fashion.
       *
       * @param forEncryption if true the cipher is initialised for
       *  encryption, if false for decryption.
       * @param params the key and other data required by the cipher.
       * @exception IllegalArgumentException if the params argument is
       * inappropriate.
       */
      public void init(
          boolean forEncryption,
          CipherParameters params)
          throws IllegalArgumentException
      {
          this.forEncryption = forEncryption;
       
          if (params instanceof ParametersWithIV)
          {
                  ParametersWithIV ivParam = (ParametersWithIV)params;
                  byte[]      iv = ivParam.getIV();
  
                  if (iv.length < IV.length)
                  {
                      // prepend the supplied IV with zeros (per FIPS PUB 81)
                      System.arraycopy(iv, 0, IV, IV.length - iv.length, iv.length);
                      for (int i = 0; i < IV.length - iv.length; i++)
                      {
                              IV[i] = 0;
                      }
                  }
                  else
                  {
                      System.arraycopy(iv, 0, IV, 0, IV.length);
                  }
  
                  reset();
  
                  cipher.init(true, ivParam.getParameters());
          }
          else
          {
                  reset();
  
                  cipher.init(true, params);
          }
      }
      
      /**
       * Encrypt one byte of data according to CFB mode.
       * @param data the byte to encrypt
       * @param where am i in the current block, determines when to resync the block
       * @returns the encrypted byte
       */
      private byte encryptByte(byte data, int blockOff)
      {
          return (byte)(FRE[blockOff] ^ data);
      }
      
      /**
       * Do the appropriate processing for CFB IV mode encryption.
       *
       * @param in the array containing the data to be encrypted.
       * @param inOff offset into the in array the data starts at.
       * @param out the array the encrypted data will be copied into.
       * @param outOff the offset into the out array the output will start at.
       * @exception DataLengthException if there isn't enough data in in, or
       * space in out.
       * @exception IllegalStateException if the cipher isn't initialised.
       * @return the number of bytes processed and produced.
       */
      private int encryptBlockWithIV(
          byte[] in,
          int inOff,
          byte[] out,
          int outOff)
          throws DataLengthException, IllegalStateException
      {
          if ((inOff + blockSize) > in.length)
          {
              throw new DataLengthException("input buffer too short");
          }
  
          if ((outOff + blockSize) > out.length)
          {
              throw new DataLengthException("output buffer too short");
          }
          
          if (count == 0)
          {
              cipher.processBlock(FR, 0, FRE, 0);
  
              for (int n = 0; n < blockSize; n++) 
              {
                  out[outOff + n] = encryptByte(IV[n], n);
              }
              
              System.arraycopy(out, outOff, FR, 0, blockSize);
  
              cipher.processBlock(FR, 0, FRE, 0);
  
              out[outOff + blockSize] = encryptByte(IV[blockSize - 2], 0);
              out[outOff + blockSize + 1] = encryptByte(IV[blockSize - 1], 1);
  
              System.arraycopy(out, outOff + 2, FR, 0, blockSize);
              
              cipher.processBlock(FR, 0, FRE, 0);
  
              for (int n = 0; n < blockSize; n++) 
              {
                  out[outOff + blockSize + 2 + n] = encryptByte(in[inOff + n], n);
              }
  
              System.arraycopy(out, outOff + blockSize + 2, FR, 0, blockSize);
  
              count += 2 * blockSize + 2;
  
              return 2 * blockSize + 2;
          }
          else if (count >= blockSize + 2)
          {
              cipher.processBlock(FR, 0, FRE, 0);
  
              for (int n = 0; n < blockSize; n++) 
              {
                  out[outOff + n] = encryptByte(in[inOff + n], n);
              }
              
              System.arraycopy(out, outOff, FR, 0, blockSize);
          }
          
          return blockSize;
      }
  
      /**
       * Do the appropriate processing for CFB IV mode decryption.
       *
       * @param in the array containing the data to be decrypted.
       * @param inOff offset into the in array the data starts at.
       * @param out the array the encrypted data will be copied into.
       * @param outOff the offset into the out array the output will start at.
       * @exception DataLengthException if there isn't enough data in in, or
       * space in out.
       * @exception IllegalStateException if the cipher isn't initialised.
       * @return the number of bytes processed and produced.
       */
      private int decryptBlockWithIV(
          byte[] in,
          int inOff,
          byte[] out,
          int outOff)
          throws DataLengthException, IllegalStateException
      {
          if ((inOff + blockSize) > in.length)
          {
              throw new DataLengthException("input buffer too short");
          }
  
          if ((outOff + blockSize) > out.length)
          {
              throw new DataLengthException("output buffer too short");
          }
          
          if (count == 0)
          {
              for (int n = 0; n < blockSize; n++) 
              {
                  FR[n] = in[inOff + n];
              }
              
              cipher.processBlock(FR, 0, FRE, 0);
  
              count += blockSize;
  
              return 0;
          }
          else if (count == blockSize)
          {
              // copy in buffer so that this mode works if in and out are the same 
              System.arraycopy(in, inOff, tmp, 0, blockSize);
          
              System.arraycopy(FR, 2, FR, 0, blockSize - 2);
              
              FR[blockSize - 2] = tmp[0];
              FR[blockSize - 1] = tmp[1];
  
              cipher.processBlock(FR, 0, FRE, 0);
  
              for (int n = 0; n < blockSize - 2; n++) 
              {
                  out[outOff + n] = encryptByte(tmp[n + 2], n);
              }
  
              System.arraycopy(tmp, 2, FR, 0, blockSize - 2);
  
              count += 2;
  
              return blockSize - 2;
          }
          else if (count >= blockSize + 2)
          {
              // copy in buffer so that this mode works if in and out are the same 
              System.arraycopy(in, inOff, tmp, 0, blockSize);
  
              out[outOff + 0] = encryptByte(tmp[0], blockSize - 2);
              out[outOff + 1] = encryptByte(tmp[1], blockSize - 1);
  
              System.arraycopy(tmp, 0, FR, blockSize - 2, 2);
  
              cipher.processBlock(FR, 0, FRE, 0);
              
              for (int n = 0; n < blockSize - 2; n++) 
              {
                  out[outOff + n + 2] = encryptByte(tmp[n + 2], n);
              }
              
              System.arraycopy(tmp, 2, FR, 0, blockSize - 2);
              
          } 
          
          return blockSize;
      }
      
      /**
       * Do the appropriate processing for CFB mode encryption.
       *
       * @param in the array containing the data to be encrypted.
       * @param inOff offset into the in array the data starts at.
       * @param out the array the encrypted data will be copied into.
       * @param outOff the offset into the out array the output will start at.
       * @exception DataLengthException if there isn't enough data in in, or
       * space in out.
       * @exception IllegalStateException if the cipher isn't initialised.
       * @return the number of bytes processed and produced.
       */
      private int encryptBlock(
          byte[] in,
          int inOff,
          byte[] out,
          int outOff)
          throws DataLengthException, IllegalStateException
      {        
          if ((inOff + blockSize) > in.length)
          {
              throw new DataLengthException("input buffer too short");
          }
  
          if ((outOff + blockSize) > out.length)
          {
              throw new DataLengthException("output buffer too short");
          }
          
          cipher.processBlock(FR, 0, FRE, 0);
          for (int n = 0; n < blockSize; n++) 
          {
              out[outOff + n] = encryptByte(in[inOff + n], n);
          }
          
          for (int n = 0; n < blockSize; n++) 
          {
              FR[n] = out[outOff + n];
          }
          
          return blockSize;
          
      }
      
      /**
       * Do the appropriate processing for CFB mode decryption.
       *
       * @param in the array containing the data to be decrypted.
       * @param inOff offset into the in array the data starts at.
       * @param out the array the encrypted data will be copied into.
       * @param outOff the offset into the out array the output will start at.
       * @exception DataLengthException if there isn't enough data in in, or
       * space in out.
       * @exception IllegalStateException if the cipher isn't initialised.
       * @return the number of bytes processed and produced.
       */
      private int decryptBlock(
          byte[] in,
          int inOff,
          byte[] out,
          int outOff)
          throws DataLengthException, IllegalStateException
      {
          if ((inOff + blockSize) > in.length)
          {
              throw new DataLengthException("input buffer too short");
          }
  
          if ((outOff + blockSize) > out.length)
          {
              throw new DataLengthException("output buffer too short");
          }
          
          cipher.processBlock(FR, 0, FRE, 0);
  