1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
|
using System;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Engines
{
/**
* support class for constructing intergrated encryption ciphers
* for doing basic message exchanges on top of key agreement ciphers
*/
public class IesEngine
{
private readonly IBasicAgreement agree;
private readonly IDerivationFunction kdf;
private readonly IMac mac;
private readonly BufferedBlockCipher cipher;
private readonly byte[] macBuf;
private bool forEncryption;
private ICipherParameters privParam, pubParam;
private IesParameters param;
/**
* set up for use with stream mode, where the key derivation function
* is used to provide a stream of bytes to xor with the message.
*
* @param agree the key agreement used as the basis for the encryption
* @param kdf the key derivation function used for byte generation
* @param mac the message authentication code generator for the message
*/
public IesEngine(
IBasicAgreement agree,
IDerivationFunction kdf,
IMac mac)
{
this.agree = agree;
this.kdf = kdf;
this.mac = mac;
this.macBuf = new byte[mac.GetMacSize()];
// this.cipher = null;
}
/**
* set up for use in conjunction with a block cipher to handle the
* message.
*
* @param agree the key agreement used as the basis for the encryption
* @param kdf the key derivation function used for byte generation
* @param mac the message authentication code generator for the message
* @param cipher the cipher to used for encrypting the message
*/
public IesEngine(
IBasicAgreement agree,
IDerivationFunction kdf,
IMac mac,
BufferedBlockCipher cipher)
{
this.agree = agree;
this.kdf = kdf;
this.mac = mac;
this.macBuf = new byte[mac.GetMacSize()];
this.cipher = cipher;
}
/**
* Initialise the encryptor.
*
* @param forEncryption whether or not this is encryption/decryption.
* @param privParam our private key parameters
* @param pubParam the recipient's/sender's public key parameters
* @param param encoding and derivation parameters.
*/
public virtual void Init(
bool forEncryption,
ICipherParameters privParameters,
ICipherParameters pubParameters,
ICipherParameters iesParameters)
{
this.forEncryption = forEncryption;
this.privParam = privParameters;
this.pubParam = pubParameters;
this.param = (IesParameters)iesParameters;
}
private byte[] DecryptBlock(
byte[] in_enc,
int inOff,
int inLen,
byte[] z)
{
byte[] M = null;
KeyParameter macKey = null;
KdfParameters kParam = new KdfParameters(z, param.GetDerivationV());
int macKeySize = param.MacKeySize;
kdf.Init(kParam);
// Ensure that the length of the input is greater than the MAC in bytes
if (inLen < mac.GetMacSize())
throw new InvalidCipherTextException("Length of input must be greater than the MAC");
inLen -= mac.GetMacSize();
if (cipher == null) // stream mode
{
byte[] Buffer = GenerateKdfBytes(kParam, inLen + (macKeySize / 8));
M = new byte[inLen];
for (int i = 0; i != inLen; i++)
{
M[i] = (byte)(in_enc[inOff + i] ^ Buffer[i]);
}
macKey = new KeyParameter(Buffer, inLen, (macKeySize / 8));
}
else
{
int cipherKeySize = ((IesWithCipherParameters)param).CipherKeySize;
byte[] Buffer = GenerateKdfBytes(kParam, (cipherKeySize / 8) + (macKeySize / 8));
cipher.Init(false, new KeyParameter(Buffer, 0, (cipherKeySize / 8)));
M = cipher.DoFinal(in_enc, inOff, inLen);
macKey = new KeyParameter(Buffer, (cipherKeySize / 8), (macKeySize / 8));
}
byte[] macIV = param.GetEncodingV();
mac.Init(macKey);
mac.BlockUpdate(in_enc, inOff, inLen);
mac.BlockUpdate(macIV, 0, macIV.Length);
mac.DoFinal(macBuf, 0);
inOff += inLen;
byte[] T1 = Arrays.CopyOfRange(in_enc, inOff, inOff + macBuf.Length);
if (!Arrays.FixedTimeEquals(T1, macBuf))
throw new InvalidCipherTextException("Invalid MAC.");
return M;
}
private byte[] EncryptBlock(
byte[] input,
int inOff,
int inLen,
byte[] z)
{
byte[] C = null;
KeyParameter macKey = null;
KdfParameters kParam = new KdfParameters(z, param.GetDerivationV());
int c_text_length = 0;
int macKeySize = param.MacKeySize;
if (cipher == null) // stream mode
{
byte[] Buffer = GenerateKdfBytes(kParam, inLen + (macKeySize / 8));
C = new byte[inLen + mac.GetMacSize()];
c_text_length = inLen;
for (int i = 0; i != inLen; i++)
{
C[i] = (byte)(input[inOff + i] ^ Buffer[i]);
}
macKey = new KeyParameter(Buffer, inLen, (macKeySize / 8));
}
else
{
int cipherKeySize = ((IesWithCipherParameters)param).CipherKeySize;
byte[] Buffer = GenerateKdfBytes(kParam, (cipherKeySize / 8) + (macKeySize / 8));
cipher.Init(true, new KeyParameter(Buffer, 0, (cipherKeySize / 8)));
c_text_length = cipher.GetOutputSize(inLen);
byte[] tmp = new byte[c_text_length];
int len = cipher.ProcessBytes(input, inOff, inLen, tmp, 0);
len += cipher.DoFinal(tmp, len);
C = new byte[len + mac.GetMacSize()];
c_text_length = len;
Array.Copy(tmp, 0, C, 0, len);
macKey = new KeyParameter(Buffer, (cipherKeySize / 8), (macKeySize / 8));
}
byte[] macIV = param.GetEncodingV();
mac.Init(macKey);
mac.BlockUpdate(C, 0, c_text_length);
mac.BlockUpdate(macIV, 0, macIV.Length);
//
// return the message and it's MAC
//
mac.DoFinal(C, c_text_length);
return C;
}
private byte[] GenerateKdfBytes(
KdfParameters kParam,
int length)
{
byte[] buf = new byte[length];
kdf.Init(kParam);
kdf.GenerateBytes(buf, 0, buf.Length);
return buf;
}
public virtual byte[] ProcessBlock(
byte[] input,
int inOff,
int inLen)
{
agree.Init(privParam);
BigInteger z = agree.CalculateAgreement(pubParam);
byte[] zBytes = BigIntegers.AsUnsignedByteArray(agree.GetFieldSize(), z);
try
{
return forEncryption
? EncryptBlock(input, inOff, inLen, zBytes)
: DecryptBlock(input, inOff, inLen, zBytes);
}
finally
{
Array.Clear(zBytes, 0, zBytes.Length);
}
}
}
}
|
