1 files changed, 109 insertions, 0 deletions
diff --git a/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/GCFBBlockCipher.java b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/GCFBBlockCipher.java
new file mode 100644
index 000000000..41e26fc17
--- /dev/null
+++ b/libraries/spongycastle/core/src/main/java/org/spongycastle/crypto/modes/GCFBBlockCipher.java
@@ -0,0 +1,109 @@
+package org.spongycastle.crypto.modes;
+
+import org.spongycastle.crypto.BlockCipher;
+import org.spongycastle.crypto.CipherParameters;
+import org.spongycastle.crypto.DataLengthException;
+import org.spongycastle.crypto.params.KeyParameter;
+import org.spongycastle.crypto.params.ParametersWithIV;
+import org.spongycastle.crypto.params.ParametersWithRandom;
+import org.spongycastle.crypto.params.ParametersWithSBox;
+
+/**
+ * An implementation of the GOST CFB mode with CryptoPro key meshing as described in RFC 4357.
+ */
+public class GCFBBlockCipher
+    implements BlockCipher
+{
+    private static final byte[] C =
+        {
+            0x69, 0x00, 0x72, 0x22, 0x64, (byte)0xC9, 0x04, 0x23,
+            (byte)0x8D, 0x3A, (byte)0xDB, (byte)0x96, 0x46, (byte)0xE9, 0x2A, (byte)0xC4,
+            0x18, (byte)0xFE, (byte)0xAC, (byte)0x94, 0x00, (byte)0xED, 0x07, 0x12,
+            (byte)0xC0, (byte)0x86, (byte)0xDC, (byte)0xC2, (byte)0xEF, 0x4C, (byte)0xA9, 0x2B
+        };
+
+    private final CFBBlockCipher cfbEngine;
+
+    private KeyParameter key;
+    private long         counter = 0;
+    private boolean      forEncryption;
+
+    public GCFBBlockCipher(BlockCipher engine)
+    {
+        this.cfbEngine = new CFBBlockCipher(engine, engine.getBlockSize() * 8);
+    }
+
+    public void init(boolean forEncryption, CipherParameters params)
+        throws IllegalArgumentException
+    {
+        counter = 0;
+        cfbEngine.init(forEncryption, params);
+
+        this.forEncryption = forEncryption;
+
+        if (params instanceof ParametersWithIV)
+        {
+            params = ((ParametersWithIV)params).getParameters();
+        }
+
+        if (params instanceof ParametersWithRandom)
+        {
+            params = ((ParametersWithRandom)params).getParameters();
+        }
+
+        if (params instanceof ParametersWithSBox)
+        {
+            params = ((ParametersWithSBox)params).getParameters();
+        }
+
+        key = (KeyParameter)params;
+    }
+
+    public String getAlgorithmName()
+    {
+        return "G" + cfbEngine.getAlgorithmName();
+    }
+
+    public int getBlockSize()
+    {
+        return cfbEngine.getBlockSize();
+    }
+
+    public int processBlock(byte[] in, int inOff, byte[] out, int outOff)
+        throws DataLengthException, IllegalStateException
+    {
+        if (counter > 0 && counter % 1024 == 0)
+        {
+            BlockCipher  base = cfbEngine.getUnderlyingCipher();
+
+            base.init(false, key);
+
+            byte[] nextKey = new byte[32];
+
+            base.processBlock(C, 0, nextKey, 0);
+            base.processBlock(C, 8, nextKey, 8);
+            base.processBlock(C, 16, nextKey, 16);
+            base.processBlock(C, 24, nextKey, 24);
+
+            key = new KeyParameter(nextKey);
+
+            byte[] iv = new byte[8];
+
+            base.init(true, key);
+
+            base.processBlock(cfbEngine.getCurrentIV(), 0, iv, 0);
+
+            cfbEngine.init(forEncryption, new ParametersWithIV(key, iv));
+        }
+
+        counter += cfbEngine.getBlockSize();
+
+        return cfbEngine.processBlock(in, inOff, out, outOff);
+    }
+
+    public void reset()
+    {
+        counter = 0;
+        cfbEngine.reset();
+    }
+}