initial reshuffle

3 files changed, 901 insertions, 0 deletions

diff --git a/core/src/main/java/org/bouncycastle/crypto/encodings/ISO9796d1Encoding.java b/core/src/main/java/org/bouncycastle/crypto/encodings/ISO9796d1Encoding.java
new file mode 100644
index 00000000..ec91e1ac
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/crypto/encodings/ISO9796d1Encoding.java
@@ -0,0 +1,287 @@
+package org.bouncycastle.crypto.encodings;
+
+import java.math.BigInteger;
+
+import org.bouncycastle.crypto.AsymmetricBlockCipher;
+import org.bouncycastle.crypto.CipherParameters;
+import org.bouncycastle.crypto.InvalidCipherTextException;
+import org.bouncycastle.crypto.params.ParametersWithRandom;
+import org.bouncycastle.crypto.params.RSAKeyParameters;
+
+/**
+ * ISO 9796-1 padding. Note in the light of recent results you should
+ * only use this with RSA (rather than the "simpler" Rabin keys) and you
+ * should never use it with anything other than a hash (ie. even if the
+ * message is small don't sign the message, sign it's hash) or some "random"
+ * value. See your favorite search engine for details.
+ */
+public class ISO9796d1Encoding
+    implements AsymmetricBlockCipher
+{
+    private static final BigInteger SIXTEEN = BigInteger.valueOf(16L);
+    private static final BigInteger SIX     = BigInteger.valueOf(6L);
+
+    private static byte[]    shadows = { 0xe, 0x3, 0x5, 0x8, 0x9, 0x4, 0x2, 0xf,
+                                    0x0, 0xd, 0xb, 0x6, 0x7, 0xa, 0xc, 0x1 };
+    private static byte[]    inverse = { 0x8, 0xf, 0x6, 0x1, 0x5, 0x2, 0xb, 0xc,
+                                    0x3, 0x4, 0xd, 0xa, 0xe, 0x9, 0x0, 0x7 };
+
+    private AsymmetricBlockCipher   engine;
+    private boolean                 forEncryption;
+    private int                     bitSize;
+    private int                     padBits = 0;
+    private BigInteger              modulus;
+
+    public ISO9796d1Encoding(
+        AsymmetricBlockCipher   cipher)
+    {
+        this.engine = cipher;
+    }
+
+    public AsymmetricBlockCipher getUnderlyingCipher()
+    {
+        return engine;
+    }
+
+    public void init(
+        boolean             forEncryption,
+        CipherParameters    param)
+    {
+        RSAKeyParameters  kParam = null;
+
+        if (param instanceof ParametersWithRandom)
+        {
+            ParametersWithRandom    rParam = (ParametersWithRandom)param;
+
+            kParam = (RSAKeyParameters)rParam.getParameters();
+        }
+        else
+        {
+            kParam = (RSAKeyParameters)param;
+        }
+
+        engine.init(forEncryption, param);
+
+        modulus = kParam.getModulus();
+        bitSize = modulus.bitLength();
+
+        this.forEncryption = forEncryption;
+    }
+
+    /**
+     * return the input block size. The largest message we can process
+     * is (key_size_in_bits + 3)/16, which in our world comes to
+     * key_size_in_bytes / 2.
+     */
+    public int getInputBlockSize()
+    {
+        int     baseBlockSize = engine.getInputBlockSize();
+
+        if (forEncryption)
+        {
+            return (baseBlockSize + 1) / 2;
+        }
+        else
+        {
+            return baseBlockSize;
+        }
+    }
+
+    /**
+     * return the maximum possible size for the output.
+     */
+    public int getOutputBlockSize()
+    {
+        int     baseBlockSize = engine.getOutputBlockSize();
+
+        if (forEncryption)
+        {
+            return baseBlockSize;
+        }
+        else
+        {
+            return (baseBlockSize + 1) / 2;
+        }
+    }
+
+    /**
+     * set the number of bits in the next message to be treated as
+     * pad bits.
+     */
+    public void setPadBits(
+        int     padBits)
+    {
+        if (padBits > 7)
+        {
+            throw new IllegalArgumentException("padBits > 7");
+        }
+
+        this.padBits = padBits;
+    }
+
+    /**
+     * retrieve the number of pad bits in the last decoded message.
+     */
+    public int getPadBits()
+    {
+        return padBits;
+    }
+
+    public byte[] processBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        if (forEncryption)
+        {
+            return encodeBlock(in, inOff, inLen);
+        }
+        else
+        {
+            return decodeBlock(in, inOff, inLen);
+        }
+    }
+
+    private byte[] encodeBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        byte[]  block = new byte[(bitSize + 7) / 8];
+        int     r = padBits + 1;
+        int     z = inLen;
+        int     t = (bitSize + 13) / 16;
+
+        for (int i = 0; i < t; i += z)
+        {
+            if (i > t - z)
+            {
+                System.arraycopy(in, inOff + inLen - (t - i),
+                                    block, block.length - t, t - i);
+            }
+            else
+            {
+                System.arraycopy(in, inOff, block, block.length - (i + z), z);
+            }
+        }
+
+        for (int i = block.length - 2 * t; i != block.length; i += 2)
+        {
+            byte    val = block[block.length - t + i / 2];
+
+            block[i] = (byte)((shadows[(val & 0xff) >>> 4] << 4)
+                                                | shadows[val & 0x0f]);
+            block[i + 1] = val;
+        }
+
+        block[block.length - 2 * z] ^= r;
+        block[block.length - 1] = (byte)((block[block.length - 1] << 4) | 0x06);
+
+        int maxBit = (8 - (bitSize - 1) % 8);
+        int offSet = 0;
+
+        if (maxBit != 8)
+        {
+            block[0] &= 0xff >>> maxBit;
+            block[0] |= 0x80 >>> maxBit;
+        }
+        else
+        {
+            block[0] = 0x00;
+            block[1] |= 0x80;
+            offSet = 1;
+        }
+
+        return engine.processBlock(block, offSet, block.length - offSet);
+    }
+
+    /**
+     * @exception InvalidCipherTextException if the decrypted block is not a valid ISO 9796 bit string
+     */
+    private byte[] decodeBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        byte[]  block = engine.processBlock(in, inOff, inLen);
+        int     r = 1;
+        int     t = (bitSize + 13) / 16;
+
+        BigInteger iS = new BigInteger(1, block);
+        BigInteger iR;
+        if (iS.mod(SIXTEEN).equals(SIX))
+        {
+            iR = iS;
+        }
+        else if ((modulus.subtract(iS)).mod(SIXTEEN).equals(SIX))
+        {
+            iR = modulus.subtract(iS);
+        }
+        else
+        {
+            throw new InvalidCipherTextException("resulting integer iS or (modulus - iS) is not congruent to 6 mod 16");
+        }
+
+        block = convertOutputDecryptOnly(iR);
+
+        if ((block[block.length - 1] & 0x0f) != 0x6 )
+        {
+            throw new InvalidCipherTextException("invalid forcing byte in block");
+        }
+
+        block[block.length - 1] = (byte)(((block[block.length - 1] & 0xff) >>> 4) | ((inverse[(block[block.length - 2] & 0xff) >> 4]) << 4));
+        block[0] = (byte)((shadows[(block[1] & 0xff) >>> 4] << 4)
+                                                | shadows[block[1] & 0x0f]);
+
+        boolean boundaryFound = false;
+        int     boundary = 0;
+
+        for (int i = block.length - 1; i >= block.length - 2 * t; i -= 2)
+        {
+            int val = ((shadows[(block[i] & 0xff) >>> 4] << 4)
+                                        | shadows[block[i] & 0x0f]);
+
+            if (((block[i - 1] ^ val) & 0xff) != 0)
+            {
+                if (!boundaryFound)
+                {
+                    boundaryFound = true;
+                    r = (block[i - 1] ^ val) & 0xff;
+                    boundary = i - 1;
+                }
+                else
+                {
+                    throw new InvalidCipherTextException("invalid tsums in block");
+                }
+            }
+        }
+
+        block[boundary] = 0;
+
+        byte[]  nblock = new byte[(block.length - boundary) / 2];
+
+        for (int i = 0; i < nblock.length; i++)
+        {
+            nblock[i] = block[2 * i + boundary + 1];
+        }
+
+        padBits = r - 1;
+
+        return nblock;
+    }
+
+    private static byte[] convertOutputDecryptOnly(BigInteger result)
+    {
+        byte[] output = result.toByteArray();
+        if (output[0] == 0) // have ended up with an extra zero byte, copy down.
+        {
+            byte[] tmp = new byte[output.length - 1];
+            System.arraycopy(output, 1, tmp, 0, tmp.length);
+            return tmp;
+        }
+        return output;
+    }
+}
diff --git a/core/src/main/java/org/bouncycastle/crypto/encodings/OAEPEncoding.java b/core/src/main/java/org/bouncycastle/crypto/encodings/OAEPEncoding.java
new file mode 100644
index 00000000..17d8e3b0
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/crypto/encodings/OAEPEncoding.java
@@ -0,0 +1,357 @@
+package org.bouncycastle.crypto.encodings;
+
+import java.security.SecureRandom;
+
+import org.bouncycastle.crypto.AsymmetricBlockCipher;
+import org.bouncycastle.crypto.CipherParameters;
+import org.bouncycastle.crypto.Digest;
+import org.bouncycastle.crypto.InvalidCipherTextException;
+import org.bouncycastle.crypto.digests.SHA1Digest;
+import org.bouncycastle.crypto.params.ParametersWithRandom;
+
+/**
+ * Optimal Asymmetric Encryption Padding (OAEP) - see PKCS 1 V 2.
+ */
+public class OAEPEncoding
+    implements AsymmetricBlockCipher
+{
+    private byte[]                  defHash;
+    private Digest                  mgf1Hash;
+
+    private AsymmetricBlockCipher   engine;
+    private SecureRandom            random;
+    private boolean                 forEncryption;
+
+    public OAEPEncoding(
+        AsymmetricBlockCipher   cipher)
+    {
+        this(cipher, new SHA1Digest(), null);
+    }
+    
+    public OAEPEncoding(
+        AsymmetricBlockCipher       cipher,
+        Digest                      hash)
+    {
+        this(cipher, hash, null);
+    }
+    
+    public OAEPEncoding(
+        AsymmetricBlockCipher       cipher,
+        Digest                      hash,
+        byte[]                      encodingParams)
+    {
+        this(cipher, hash, hash, encodingParams);
+    }
+
+    public OAEPEncoding(
+        AsymmetricBlockCipher       cipher,
+        Digest                      hash,
+        Digest                      mgf1Hash,
+        byte[]                      encodingParams)
+    {
+        this.engine = cipher;
+        this.mgf1Hash = mgf1Hash;
+        this.defHash = new byte[hash.getDigestSize()];
+
+        hash.reset();
+
+        if (encodingParams != null)
+        {
+            hash.update(encodingParams, 0, encodingParams.length);
+        }
+
+        hash.doFinal(defHash, 0);
+    }
+
+    public AsymmetricBlockCipher getUnderlyingCipher()
+    {
+        return engine;
+    }
+
+    public void init(
+        boolean             forEncryption,
+        CipherParameters    param)
+    {
+        if (param instanceof ParametersWithRandom)
+        {
+            ParametersWithRandom  rParam = (ParametersWithRandom)param;
+
+            this.random = rParam.getRandom();
+        }
+        else
+        {   
+            this.random = new SecureRandom();
+        }
+
+        engine.init(forEncryption, param);
+
+        this.forEncryption = forEncryption;
+    }
+
+    public int getInputBlockSize()
+    {
+        int     baseBlockSize = engine.getInputBlockSize();
+
+        if (forEncryption)
+        {
+            return baseBlockSize - 1 - 2 * defHash.length;
+        }
+        else
+        {
+            return baseBlockSize;
+        }
+    }
+
+    public int getOutputBlockSize()
+    {
+        int     baseBlockSize = engine.getOutputBlockSize();
+
+        if (forEncryption)
+        {
+            return baseBlockSize;
+        }
+        else
+        {
+            return baseBlockSize - 1 - 2 * defHash.length;
+        }
+    }
+
+    public byte[] processBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        if (forEncryption)
+        {
+            return encodeBlock(in, inOff, inLen);
+        }
+        else
+        {
+            return decodeBlock(in, inOff, inLen);
+        }
+    }
+
+    public byte[] encodeBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        byte[]  block = new byte[getInputBlockSize() + 1 + 2 * defHash.length];
+
+        //
+        // copy in the message
+        //
+        System.arraycopy(in, inOff, block, block.length - inLen, inLen);
+
+        //
+        // add sentinel
+        //
+        block[block.length - inLen - 1] = 0x01;
+
+        //
+        // as the block is already zeroed - there's no need to add PS (the >= 0 pad of 0)
+        //
+
+        //
+        // add the hash of the encoding params.
+        //
+        System.arraycopy(defHash, 0, block, defHash.length, defHash.length);
+
+        //
+        // generate the seed.
+        //
+        byte[]  seed = new byte[defHash.length];
+
+        random.nextBytes(seed);
+
+        //
+        // mask the message block.
+        //
+        byte[]  mask = maskGeneratorFunction1(seed, 0, seed.length, block.length - defHash.length);
+
+        for (int i = defHash.length; i != block.length; i++)
+        {
+            block[i] ^= mask[i - defHash.length];
+        }
+
+        //
+        // add in the seed
+        //
+        System.arraycopy(seed, 0, block, 0, defHash.length);
+
+        //
+        // mask the seed.
+        //
+        mask = maskGeneratorFunction1(
+                        block, defHash.length, block.length - defHash.length, defHash.length);
+
+        for (int i = 0; i != defHash.length; i++)
+        {
+            block[i] ^= mask[i];
+        }
+
+        return engine.processBlock(block, 0, block.length);
+    }
+
+    /**
+     * @exception InvalidCipherTextException if the decrypted block turns out to
+     * be badly formatted.
+     */
+    public byte[] decodeBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        byte[]  data = engine.processBlock(in, inOff, inLen);
+        byte[]  block;
+
+        //
+        // as we may have zeros in our leading bytes for the block we produced
+        // on encryption, we need to make sure our decrypted block comes back
+        // the same size.
+        //
+        if (data.length < engine.getOutputBlockSize())
+        {
+            block = new byte[engine.getOutputBlockSize()];
+
+            System.arraycopy(data, 0, block, block.length - data.length, data.length);
+        }
+        else
+        {
+            block = data;
+        }
+
+        if (block.length < (2 * defHash.length) + 1)
+        {
+            throw new InvalidCipherTextException("data too short");
+        }
+
+        //
+        // unmask the seed.
+        //
+        byte[] mask = maskGeneratorFunction1(
+                    block, defHash.length, block.length - defHash.length, defHash.length);
+
+        for (int i = 0; i != defHash.length; i++)
+        {
+            block[i] ^= mask[i];
+        }
+
+        //
+        // unmask the message block.
+        //
+        mask = maskGeneratorFunction1(block, 0, defHash.length, block.length - defHash.length);
+
+        for (int i = defHash.length; i != block.length; i++)
+        {
+            block[i] ^= mask[i - defHash.length];
+        }
+
+        //
+        // check the hash of the encoding params.
+        // long check to try to avoid this been a source of a timing attack.
+        //
+        boolean defHashWrong = false;
+
+        for (int i = 0; i != defHash.length; i++)
+        {
+            if (defHash[i] != block[defHash.length + i])
+            {
+                defHashWrong = true;
+            }
+        }
+
+        if (defHashWrong)
+        {
+            throw new InvalidCipherTextException("data hash wrong");
+        }
+
+        //
+        // find the data block
+        //
+        int start;
+
+        for (start = 2 * defHash.length; start != block.length; start++)
+        {
+            if (block[start] != 0)
+            {
+                break;
+            }
+        }
+
+        if (start >= (block.length - 1) || block[start] != 1)
+        {
+            throw new InvalidCipherTextException("data start wrong " + start);
+        }
+
+        start++;
+
+        //
+        // extract the data block
+        //
+        byte[]  output = new byte[block.length - start];
+
+        System.arraycopy(block, start, output, 0, output.length);
+
+        return output;
+    }
+
+    /**
+     * int to octet string.
+     */
+    private void ItoOSP(
+        int     i,
+        byte[]  sp)
+    {
+        sp[0] = (byte)(i >>> 24);
+        sp[1] = (byte)(i >>> 16);
+        sp[2] = (byte)(i >>> 8);
+        sp[3] = (byte)(i >>> 0);
+    }
+
+    /**
+     * mask generator function, as described in PKCS1v2.
+     */
+    private byte[] maskGeneratorFunction1(
+        byte[]  Z,
+        int     zOff,
+        int     zLen,
+        int     length)
+    {
+        byte[]  mask = new byte[length];
+        byte[]  hashBuf = new byte[mgf1Hash.getDigestSize()];
+        byte[]  C = new byte[4];
+        int     counter = 0;
+
+        mgf1Hash.reset();
+
+        while (counter < (length / hashBuf.length))
+        {
+            ItoOSP(counter, C);
+
+            mgf1Hash.update(Z, zOff, zLen);
+            mgf1Hash.update(C, 0, C.length);
+            mgf1Hash.doFinal(hashBuf, 0);
+
+            System.arraycopy(hashBuf, 0, mask, counter * hashBuf.length, hashBuf.length);
+
+            counter++;
+        }
+
+        if ((counter * hashBuf.length) < length)
+        {
+            ItoOSP(counter, C);
+
+            mgf1Hash.update(Z, zOff, zLen);
+            mgf1Hash.update(C, 0, C.length);
+            mgf1Hash.doFinal(hashBuf, 0);
+
+            System.arraycopy(hashBuf, 0, mask, counter * hashBuf.length, mask.length - (counter * hashBuf.length));
+        }
+
+        return mask;
+    }
+}
diff --git a/core/src/main/java/org/bouncycastle/crypto/encodings/PKCS1Encoding.java b/core/src/main/java/org/bouncycastle/crypto/encodings/PKCS1Encoding.java
new file mode 100644
index 00000000..09f1537e
--- /dev/null
+++ b/core/src/main/java/org/bouncycastle/crypto/encodings/PKCS1Encoding.java
@@ -0,0 +1,257 @@
+package org.bouncycastle.crypto.encodings;
+
+import java.security.AccessController;
+import java.security.PrivilegedAction;
+import java.security.SecureRandom;
+
+import org.bouncycastle.crypto.AsymmetricBlockCipher;
+import org.bouncycastle.crypto.CipherParameters;
+import org.bouncycastle.crypto.InvalidCipherTextException;
+import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
+import org.bouncycastle.crypto.params.ParametersWithRandom;
+
+/**
+ * this does your basic PKCS 1 v1.5 padding - whether or not you should be using this
+ * depends on your application - see PKCS1 Version 2 for details.
+ */
+public class PKCS1Encoding
+    implements AsymmetricBlockCipher
+{
+    /**
+     * some providers fail to include the leading zero in PKCS1 encoded blocks. If you need to
+     * work with one of these set the system property org.bouncycastle.pkcs1.strict to false.
+     * <p>
+     * The system property is checked during construction of the encoding object, it is set to 
+     * true by default.
+     * </p>
+     */
+    public static final String STRICT_LENGTH_ENABLED_PROPERTY = "org.bouncycastle.pkcs1.strict";
+    
+    private static final int HEADER_LENGTH = 10;
+
+    private SecureRandom            random;
+    private AsymmetricBlockCipher   engine;
+    private boolean                 forEncryption;
+    private boolean                 forPrivateKey;
+    private boolean                 useStrictLength;
+
+    /**
+     * Basic constructor.
+     * @param cipher
+     */
+    public PKCS1Encoding(
+        AsymmetricBlockCipher   cipher)
+    {
+        this.engine = cipher;
+        this.useStrictLength = useStrict();
+    }   
+
+    //
+    // for J2ME compatibility
+    //
+    private boolean useStrict()
+    {
+        // required if security manager has been installed.
+        String strict = (String)AccessController.doPrivileged(new PrivilegedAction()
+        {
+            public Object run()
+            {
+                return System.getProperty(STRICT_LENGTH_ENABLED_PROPERTY);
+            }
+        });
+
+        return strict == null || strict.equals("true");
+    }
+
+    public AsymmetricBlockCipher getUnderlyingCipher()
+    {
+        return engine;
+    }
+
+    public void init(
+        boolean             forEncryption,
+        CipherParameters    param)
+    {
+        AsymmetricKeyParameter  kParam;
+
+        if (param instanceof ParametersWithRandom)
+        {
+            ParametersWithRandom    rParam = (ParametersWithRandom)param;
+
+            this.random = rParam.getRandom();
+            kParam = (AsymmetricKeyParameter)rParam.getParameters();
+        }
+        else
+        {
+            this.random = new SecureRandom();
+            kParam = (AsymmetricKeyParameter)param;
+        }
+
+        engine.init(forEncryption, param);
+
+        this.forPrivateKey = kParam.isPrivate();
+        this.forEncryption = forEncryption;
+    }
+
+    public int getInputBlockSize()
+    {
+        int     baseBlockSize = engine.getInputBlockSize();
+
+        if (forEncryption)
+        {
+            return baseBlockSize - HEADER_LENGTH;
+        }
+        else
+        {
+            return baseBlockSize;
+        }
+    }
+
+    public int getOutputBlockSize()
+    {
+        int     baseBlockSize = engine.getOutputBlockSize();
+
+        if (forEncryption)
+        {
+            return baseBlockSize;
+        }
+        else
+        {
+            return baseBlockSize - HEADER_LENGTH;
+        }
+    }
+
+    public byte[] processBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        if (forEncryption)
+        {
+            return encodeBlock(in, inOff, inLen);
+        }
+        else
+        {
+            return decodeBlock(in, inOff, inLen);
+        }
+    }
+
+    private byte[] encodeBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        if (inLen > getInputBlockSize())
+        {
+            throw new IllegalArgumentException("input data too large");
+        }
+        
+        byte[]  block = new byte[engine.getInputBlockSize()];
+
+        if (forPrivateKey)
+        {
+            block[0] = 0x01;                        // type code 1
+
+            for (int i = 1; i != block.length - inLen - 1; i++)
+            {
+                block[i] = (byte)0xFF;
+            }
+        }
+        else
+        {
+            random.nextBytes(block);                // random fill
+
+            block[0] = 0x02;                        // type code 2
+
+            //
+            // a zero byte marks the end of the padding, so all
+            // the pad bytes must be non-zero.
+            //
+            for (int i = 1; i != block.length - inLen - 1; i++)
+            {
+                while (block[i] == 0)
+                {
+                    block[i] = (byte)random.nextInt();
+                }
+            }
+        }
+
+        block[block.length - inLen - 1] = 0x00;       // mark the end of the padding
+        System.arraycopy(in, inOff, block, block.length - inLen, inLen);
+
+        return engine.processBlock(block, 0, block.length);
+    }
+
+    /**
+     * @exception InvalidCipherTextException if the decrypted block is not in PKCS1 format.
+     */
+    private byte[] decodeBlock(
+        byte[]  in,
+        int     inOff,
+        int     inLen)
+        throws InvalidCipherTextException
+    {
+        byte[]  block = engine.processBlock(in, inOff, inLen);
+
+        if (block.length < getOutputBlockSize())
+        {
+            throw new InvalidCipherTextException("block truncated");
+        }
+
+        byte type = block[0];
+
+        if (forPrivateKey)
+        {
+            if (type != 2)
+            {
+                throw new InvalidCipherTextException("unknown block type");
+            }
+        }
+        else
+        {
+            if (type != 1)
+            {
+                throw new InvalidCipherTextException("unknown block type");
+            }
+        }
+
+        if (useStrictLength && block.length != engine.getOutputBlockSize())
+        {
+            throw new InvalidCipherTextException("block incorrect size");
+        }
+        
+        //
+        // find and extract the message block.
+        //
+        int start;
+        
+        for (start = 1; start != block.length; start++)
+        {
+            byte pad = block[start];
+            
+            if (pad == 0)
+            {
+                break;
+            }
+            if (type == 1 && pad != (byte)0xff)
+            {
+                throw new InvalidCipherTextException("block padding incorrect");
+            }
+        }
+
+        start++;           // data should start at the next byte
+
+        if (start > block.length || start < HEADER_LENGTH)
+        {
+            throw new InvalidCipherTextException("no data in block");
+        }
+
+        byte[]  result = new byte[block.length - start];
+
+        System.arraycopy(block, start, result, 0, result.length);
+
+        return result;
+    }
+}