1 package org.bouncycastle.crypto.engines;
2 
3 import org.bouncycastle.crypto.BlockCipher;
4 import org.bouncycastle.crypto.CipherParameters;
5 import org.bouncycastle.crypto.DataLengthException;
6 import org.bouncycastle.crypto.OutputLengthException;
7 import org.bouncycastle.crypto.params.KeyParameter;
8 
9 /**
10  * a class that provides a basic SKIPJACK engine.
11  */
12 public class SkipjackEngine
13     implements BlockCipher
14 {
15     static final int BLOCK_SIZE = 8;
16 
17     static short ftable[] =
18     {
19         0xa3, 0xd7, 0x09, 0x83, 0xf8, 0x48, 0xf6, 0xf4, 0xb3, 0x21, 0x15, 0x78, 0x99, 0xb1, 0xaf, 0xf9,
20         0xe7, 0x2d, 0x4d, 0x8a, 0xce, 0x4c, 0xca, 0x2e, 0x52, 0x95, 0xd9, 0x1e, 0x4e, 0x38, 0x44, 0x28,
21         0x0a, 0xdf, 0x02, 0xa0, 0x17, 0xf1, 0x60, 0x68, 0x12, 0xb7, 0x7a, 0xc3, 0xe9, 0xfa, 0x3d, 0x53,
22         0x96, 0x84, 0x6b, 0xba, 0xf2, 0x63, 0x9a, 0x19, 0x7c, 0xae, 0xe5, 0xf5, 0xf7, 0x16, 0x6a, 0xa2,
23         0x39, 0xb6, 0x7b, 0x0f, 0xc1, 0x93, 0x81, 0x1b, 0xee, 0xb4, 0x1a, 0xea, 0xd0, 0x91, 0x2f, 0xb8,
24         0x55, 0xb9, 0xda, 0x85, 0x3f, 0x41, 0xbf, 0xe0, 0x5a, 0x58, 0x80, 0x5f, 0x66, 0x0b, 0xd8, 0x90,
25         0x35, 0xd5, 0xc0, 0xa7, 0x33, 0x06, 0x65, 0x69, 0x45, 0x00, 0x94, 0x56, 0x6d, 0x98, 0x9b, 0x76,
26         0x97, 0xfc, 0xb2, 0xc2, 0xb0, 0xfe, 0xdb, 0x20, 0xe1, 0xeb, 0xd6, 0xe4, 0xdd, 0x47, 0x4a, 0x1d,
27         0x42, 0xed, 0x9e, 0x6e, 0x49, 0x3c, 0xcd, 0x43, 0x27, 0xd2, 0x07, 0xd4, 0xde, 0xc7, 0x67, 0x18,
28         0x89, 0xcb, 0x30, 0x1f, 0x8d, 0xc6, 0x8f, 0xaa, 0xc8, 0x74, 0xdc, 0xc9, 0x5d, 0x5c, 0x31, 0xa4,
29         0x70, 0x88, 0x61, 0x2c, 0x9f, 0x0d, 0x2b, 0x87, 0x50, 0x82, 0x54, 0x64, 0x26, 0x7d, 0x03, 0x40,
30         0x34, 0x4b, 0x1c, 0x73, 0xd1, 0xc4, 0xfd, 0x3b, 0xcc, 0xfb, 0x7f, 0xab, 0xe6, 0x3e, 0x5b, 0xa5,
31         0xad, 0x04, 0x23, 0x9c, 0x14, 0x51, 0x22, 0xf0, 0x29, 0x79, 0x71, 0x7e, 0xff, 0x8c, 0x0e, 0xe2,
32         0x0c, 0xef, 0xbc, 0x72, 0x75, 0x6f, 0x37, 0xa1, 0xec, 0xd3, 0x8e, 0x62, 0x8b, 0x86, 0x10, 0xe8,
33         0x08, 0x77, 0x11, 0xbe, 0x92, 0x4f, 0x24, 0xc5, 0x32, 0x36, 0x9d, 0xcf, 0xf3, 0xa6, 0xbb, 0xac,
34         0x5e, 0x6c, 0xa9, 0x13, 0x57, 0x25, 0xb5, 0xe3, 0xbd, 0xa8, 0x3a, 0x01, 0x05, 0x59, 0x2a, 0x46
35     };
36 
37     private int[]       key0, key1, key2, key3;
38     private boolean     encrypting;
39 
40     /**
41      * initialise a SKIPJACK cipher.
42      *
43      * @param encrypting whether or not we are for encryption.
44      * @param params the parameters required to set up the cipher.
45      * @exception IllegalArgumentException if the params argument is
46      * inappropriate.
47      */
init( boolean encrypting, CipherParameters params)48     public void init(
49         boolean           encrypting,
50         CipherParameters  params)
51     {
52         if (!(params instanceof KeyParameter))
53         {
54         throw new IllegalArgumentException("invalid parameter passed to SKIPJACK init - " + params.getClass().getName());
55         }
56 
57         byte[] keyBytes = ((KeyParameter)params).getKey();
58 
59         this.encrypting = encrypting;
60         this.key0 = new int[32];
61         this.key1 = new int[32];
62         this.key2 = new int[32];
63         this.key3 = new int[32];
64 
65         //
66         // expand the key to 128 bytes in 4 parts (saving us a modulo, multiply
67         // and an addition).
68         //
69         for (int i = 0; i < 32; i ++)
70         {
71             key0[i] = keyBytes[(i * 4) % 10] & 0xff;
72             key1[i] = keyBytes[(i * 4 + 1) % 10] & 0xff;
73             key2[i] = keyBytes[(i * 4 + 2) % 10] & 0xff;
74             key3[i] = keyBytes[(i * 4 + 3) % 10] & 0xff;
75         }
76     }
77 
getAlgorithmName()78     public String getAlgorithmName()
79     {
80         return "SKIPJACK";
81     }
82 
getBlockSize()83     public int getBlockSize()
84     {
85         return BLOCK_SIZE;
86     }
87 
processBlock( byte[] in, int inOff, byte[] out, int outOff)88     public int processBlock(
89         byte[] in,
90         int inOff,
91         byte[] out,
92         int outOff)
93     {
94         if (key1 == null)
95         {
96             throw new IllegalStateException("SKIPJACK engine not initialised");
97         }
98 
99         if ((inOff + BLOCK_SIZE) > in.length)
100         {
101             throw new DataLengthException("input buffer too short");
102         }
103 
104         if ((outOff + BLOCK_SIZE) > out.length)
105         {
106             throw new OutputLengthException("output buffer too short");
107         }
108 
109         if (encrypting)
110         {
111             encryptBlock(in, inOff, out, outOff);
112         }
113         else
114         {
115             decryptBlock(in, inOff, out, outOff);
116         }
117 
118         return BLOCK_SIZE;
119     }
120 
reset()121     public void reset()
122     {
123     }
124 
125     /**
126      * The G permutation
127      */
g( int k, int w)128     private int g(
129         int     k,
130         int     w)
131     {
132         int g1, g2, g3, g4, g5, g6;
133 
134         g1 = (w >> 8) & 0xff;
135         g2 = w & 0xff;
136 
137         g3 = ftable[g2 ^ key0[k]] ^ g1;
138         g4 = ftable[g3 ^ key1[k]] ^ g2;
139         g5 = ftable[g4 ^ key2[k]] ^ g3;
140         g6 = ftable[g5 ^ key3[k]] ^ g4;
141 
142         return ((g5 << 8) + g6);
143     }
144 
encryptBlock( byte[] in, int inOff, byte[] out, int outOff)145     public int encryptBlock(
146         byte[]      in,
147         int         inOff,
148         byte[]      out,
149         int         outOff)
150     {
151         int w1 = (in[inOff + 0] << 8) + (in[inOff + 1] & 0xff);
152         int w2 = (in[inOff + 2] << 8) + (in[inOff + 3] & 0xff);
153         int w3 = (in[inOff + 4] << 8) + (in[inOff + 5] & 0xff);
154         int w4 = (in[inOff + 6] << 8) + (in[inOff + 7] & 0xff);
155 
156         int k = 0;
157 
158         for (int t = 0; t < 2; t++)
159         {
160             for(int i = 0; i < 8; i++)
161             {
162                 int tmp = w4;
163                 w4 = w3;
164                 w3 = w2;
165                 w2 = g(k, w1);
166                 w1 = w2 ^ tmp ^ (k + 1);
167                 k++;
168             }
169 
170             for(int i = 0; i < 8; i++)
171             {
172                 int tmp = w4;
173                 w4 = w3;
174                 w3 = w1 ^ w2 ^ (k + 1);
175                 w2 = g(k, w1);
176                 w1 = tmp;
177                 k++;
178             }
179         }
180 
181         out[outOff + 0] = (byte)((w1 >> 8));
182         out[outOff + 1] = (byte)(w1);
183         out[outOff + 2] = (byte)((w2 >> 8));
184         out[outOff + 3] = (byte)(w2);
185         out[outOff + 4] = (byte)((w3 >> 8));
186         out[outOff + 5] = (byte)(w3);
187         out[outOff + 6] = (byte)((w4 >> 8));
188         out[outOff + 7] = (byte)(w4);
189 
190         return BLOCK_SIZE;
191     }
192 
193     /**
194      * the inverse of the G permutation.
195      */
h( int k, int w)196     private int h(
197         int     k,
198         int     w)
199     {
200         int h1, h2, h3, h4, h5, h6;
201 
202         h1 = w & 0xff;
203         h2 = (w >> 8) & 0xff;
204 
205         h3 = ftable[h2 ^ key3[k]] ^ h1;
206         h4 = ftable[h3 ^ key2[k]] ^ h2;
207         h5 = ftable[h4 ^ key1[k]] ^ h3;
208         h6 = ftable[h5 ^ key0[k]] ^ h4;
209 
210         return ((h6 << 8) + h5);
211     }
212 
decryptBlock( byte[] in, int inOff, byte[] out, int outOff)213     public int decryptBlock(
214         byte[]      in,
215         int         inOff,
216         byte[]      out,
217         int         outOff)
218     {
219         int w2 = (in[inOff + 0] << 8) + (in[inOff + 1] & 0xff);
220         int w1 = (in[inOff + 2] << 8) + (in[inOff + 3] & 0xff);
221         int w4 = (in[inOff + 4] << 8) + (in[inOff + 5] & 0xff);
222         int w3 = (in[inOff + 6] << 8) + (in[inOff + 7] & 0xff);
223 
224         int k = 31;
225 
226         for (int t = 0; t < 2; t++)
227         {
228             for(int i = 0; i < 8; i++)
229             {
230                 int tmp = w4;
231                 w4 = w3;
232                 w3 = w2;
233                 w2 = h(k, w1);
234                 w1 = w2 ^ tmp ^ (k + 1);
235                 k--;
236             }
237 
238             for(int i = 0; i < 8; i++)
239             {
240                 int tmp = w4;
241                 w4 = w3;
242                 w3 = w1 ^ w2 ^ (k + 1);
243                 w2 = h(k, w1);
244                 w1 = tmp;
245                 k--;
246             }
247         }
248 
249         out[outOff + 0] = (byte)((w2 >> 8));
250         out[outOff + 1] = (byte)(w2);
251         out[outOff + 2] = (byte)((w1 >> 8));
252         out[outOff + 3] = (byte)(w1);
253         out[outOff + 4] = (byte)((w4 >> 8));
254         out[outOff + 5] = (byte)(w4);
255         out[outOff + 6] = (byte)((w3 >> 8));
256         out[outOff + 7] = (byte)(w3);
257 
258         return BLOCK_SIZE;
259     }
260 }
261