ISO10126d2Padding.java revision e6bf3e8dfa2804891a82075cb469b736321b4827 
1package org.bouncycastle.crypto.paddings;
2
3import java.security.SecureRandom;
4
5import org.bouncycastle.crypto.InvalidCipherTextException;
6
7/**
8 * A padder that adds ISO10126-2 padding to a block.
9 */
10public class ISO10126d2Padding
11    implements BlockCipherPadding
12{
13    SecureRandom    random;
14
15    /**
16     * Initialise the padder.
17     *
18     * @param random a SecureRandom if available.
19     */
20    public void init(SecureRandom random)
21        throws IllegalArgumentException
22    {
23        if (random != null)
24        {
25            this.random = random;
26        }
27        else
28        {
29            this.random = new SecureRandom();
30        }
31    }
32
33    /**
34     * Return the name of the algorithm the padder implements.
35     *
36     * @return the name of the algorithm the padder implements.
37     */
38    public String getPaddingName()
39    {
40        return "ISO10126-2";
41    }
42
43    /**
44     * add the pad bytes to the passed in block, returning the
45     * number of bytes added.
46     */
47    public int addPadding(
48        byte[]  in,
49        int     inOff)
50    {
51        byte code = (byte)(in.length - inOff);
52
53        while (inOff < (in.length - 1))
54        {
55            in[inOff] = (byte)random.nextInt();
56            inOff++;
57        }
58
59        in[inOff] = code;
60
61        return code;
62    }
63
64    /**
65     * return the number of pad bytes present in the block.
66     */
67    public int padCount(byte[] in)
68        throws InvalidCipherTextException
69    {
70        int count = in[in.length - 1] & 0xff;
71
72        if (count > in.length)
73        {
74            throw new InvalidCipherTextException("pad block corrupted");
75        }
76
77        return count;
78    }
79}
80