ISO7816d4Padding.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 the padding according to the scheme referenced in
9 * ISO 7814-4 - scheme 2 from ISO 9797-1. The first byte is 0x80, rest is 0x00
10 */
11public class ISO7816d4Padding
12    implements BlockCipherPadding
13{
14    /**
15     * Initialise the padder.
16     *
17     * @param random - a SecureRandom if available.
18     */
19    public void init(SecureRandom random)
20        throws IllegalArgumentException
21    {
22        // nothing to do.
23    }
24
25    /**
26     * Return the name of the algorithm the padder implements.
27     *
28     * @return the name of the algorithm the padder implements.
29     */
30    public String getPaddingName()
31    {
32        return "ISO7816-4";
33    }
34
35    /**
36     * add the pad bytes to the passed in block, returning the
37     * number of bytes added.
38     */
39    public int addPadding(
40        byte[]  in,
41        int     inOff)
42    {
43        int added = (in.length - inOff);
44
45        in [inOff]= (byte) 0x80;
46        inOff ++;
47
48        while (inOff < in.length)
49        {
50            in[inOff] = (byte) 0;
51            inOff++;
52        }
53
54        return added;
55    }
56
57    /**
58     * return the number of pad bytes present in the block.
59     */
60    public int padCount(byte[] in)
61        throws InvalidCipherTextException
62    {
63        int count = in.length - 1;
64
65        while (count > 0 && in[count] == 0)
66        {
67            count--;
68        }
69
70        if (in[count] != (byte)0x80)
71        {
72            throw new InvalidCipherTextException("pad block corrupted");
73        }
74
75        return in.length - count;
76    }
77}
78