Example

The following example shows an Assembly that compresses its input data, before encrypting it with a Blowfish algorithm, in OFB mode, with PKCS7 padding.

     import gnu.crypto.Registry;
     import gnu.crypto.util.Util;
     import gnu.crypto.assembly.Assembly;
     import gnu.crypto.assembly.Cascade;
     import gnu.crypto.assembly.Direction;
     import gnu.crypto.assembly.Stage;
     import gnu.crypto.assembly.Transformer;
     import gnu.crypto.assembly.TransformerException;
     import gnu.crypto.cipher.Blowfish;
     import gnu.crypto.cipher.IBlockCipher;
     import gnu.crypto.mode.IMode;
     import gnu.crypto.mode.ModeFactory;
     import gnu.crypto.pad.IPad;
     import gnu.crypto.pad.PadFactory;
     
     
     HashMap attributes = new HashMap();
     HashMap modeAttributes = new HashMap();
     
     Cascade ofbBlowfish = new Cascade();
     Object modeNdx = ofbBlowfish.append(
         Stage.getInstance(
             ModeFactory.getInstance(Registry.OFB_MODE, new Blowfish(), 8),
             Direction.FORWARD));
     
     attributes.put(modeNdx, modeAttributes);
     IPad pkcs7 = PadFactory.getInstance(Registry.PKCS7_PAD);
     
     Assembly asm = new Assembly();
     asm.addPreTransformer(Transformer.getCascadeTransformer(ofbBlowfish));
     asm.addPreTransformer(Transformer.getPaddingTransformer(pkcs7));
     asm.addPreTransformer(Transformer.getDeflateTransformer());
     
     // plaintext and key material
     byte[] km = new byte[] { 0,  1,  2,  3,  4,  5,  6,  7,  8};
     byte[] iv = new byte[] {-1, -2, -3, -4, -5, -6, -7, -8, -9};
     byte[] pt = new byte[] { 0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10,  11};
     byte[] tpt = new byte[11 * pt.length];
     
     // forward transformation
     modeAttributes.put(IBlockCipher.KEY_MATERIAL, km);
     modeAttributes.put(IMode.IV, iv);
     attributes.put(Assembly.DIRECTION, Direction.FORWARD);
     try
       {
         asm.init(attributes);
       }
     catch (TransformerException x)
       {
         x.printStackTrace(System.err);
       }
     
     byte[] ct = null;
     ByteArrayOutputStream baos = new ByteArrayOutputStream();
     try
       {
         for (int i = 0; i < 10; i++)
           { // transform in parts of 12-byte a time
             System.arraycopy(pt, 0, tpt, i * pt.length, pt.length);
             ct = asm.update(pt);
             baos.write(ct, 0, ct.length);
           }
       }
     catch (TransformerException x)
       {
         x.printStackTrace(System.err);
       }
     
     try
       {
         System.arraycopy(pt, 0, tpt, 10 * pt.length, pt.length);
         ct = asm.lastUpdate(pt);
       }
     catch (TransformerException x)
       {
         x.printStackTrace(System.err);
       }
     
     baos.write(ct, 0, ct.length);
     ct = baos.toByteArray();
     
     // reversed transformation
     attributes.put(Assembly.DIRECTION, Direction.REVERSED);
     try
       {
         asm.init(attributes);
       }
     catch (TransformerException x)
       {
         x.printStackTrace(System.err);
       }
     
     byte[] ot = null;
     try
       {
         ot = asm.lastUpdate(ct); // transform the lot in one go
       }
     catch (TransformerException x)
       {
         x.printStackTrace(System.err);
       }