diff options
Diffstat (limited to 'lib/src/main/java/com/trilead/ssh2/crypto/cipher/CBCMode.java')
-rw-r--r-- | lib/src/main/java/com/trilead/ssh2/crypto/cipher/CBCMode.java | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/lib/src/main/java/com/trilead/ssh2/crypto/cipher/CBCMode.java b/lib/src/main/java/com/trilead/ssh2/crypto/cipher/CBCMode.java new file mode 100644 index 0000000..60889f0 --- /dev/null +++ b/lib/src/main/java/com/trilead/ssh2/crypto/cipher/CBCMode.java @@ -0,0 +1,78 @@ +package com.trilead.ssh2.crypto.cipher;
+
+/**
+ * CBCMode.
+ *
+ * @author Christian Plattner, plattner@trilead.com
+ * @version $Id: CBCMode.java,v 1.1 2007/10/15 12:49:55 cplattne Exp $
+ */
+public class CBCMode implements BlockCipher
+{
+ BlockCipher tc;
+ int blockSize;
+ boolean doEncrypt;
+
+ byte[] cbc_vector;
+ byte[] tmp_vector;
+
+ public void init(boolean forEncryption, byte[] key)
+ {
+ }
+
+ public CBCMode(BlockCipher tc, byte[] iv, boolean doEncrypt)
+ throws IllegalArgumentException
+ {
+ this.tc = tc;
+ this.blockSize = tc.getBlockSize();
+ this.doEncrypt = doEncrypt;
+
+ if (this.blockSize != iv.length)
+ throw new IllegalArgumentException("IV must be " + blockSize
+ + " bytes long! (currently " + iv.length + ")");
+
+ this.cbc_vector = new byte[blockSize];
+ this.tmp_vector = new byte[blockSize];
+ System.arraycopy(iv, 0, cbc_vector, 0, blockSize);
+ }
+
+ public int getBlockSize()
+ {
+ return blockSize;
+ }
+
+ private void encryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
+ {
+ for (int i = 0; i < blockSize; i++)
+ cbc_vector[i] ^= src[srcoff + i];
+
+ tc.transformBlock(cbc_vector, 0, dst, dstoff);
+
+ System.arraycopy(dst, dstoff, cbc_vector, 0, blockSize);
+ }
+
+ private void decryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
+ {
+ /* Assume the worst, src and dst are overlapping... */
+
+ System.arraycopy(src, srcoff, tmp_vector, 0, blockSize);
+
+ tc.transformBlock(src, srcoff, dst, dstoff);
+
+ for (int i = 0; i < blockSize; i++)
+ dst[dstoff + i] ^= cbc_vector[i];
+
+ /* ...that is why we need a tmp buffer. */
+
+ byte[] swap = cbc_vector;
+ cbc_vector = tmp_vector;
+ tmp_vector = swap;
+ }
+
+ public void transformBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
+ {
+ if (doEncrypt)
+ encryptBlock(src, srcoff, dst, dstoff);
+ else
+ decryptBlock(src, srcoff, dst, dstoff);
+ }
+}
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