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package com.trilead.ssh2.crypto.digest;
/**
* HMAC.
*
* @author Christian Plattner, plattner@trilead.com
* @version $Id: HMAC.java,v 1.1 2007/10/15 12:49:57 cplattne Exp $
*/
public final class HMAC implements Digest
{
Digest md;
byte[] k_xor_ipad;
byte[] k_xor_opad;
byte[] tmp;
int size;
public HMAC(Digest md, byte[] key, int size)
{
this.md = md;
this.size = size;
tmp = new byte[md.getDigestLength()];
final int BLOCKSIZE = 64;
k_xor_ipad = new byte[BLOCKSIZE];
k_xor_opad = new byte[BLOCKSIZE];
if (key.length > BLOCKSIZE)
{
md.reset();
md.update(key);
md.digest(tmp);
key = tmp;
}
System.arraycopy(key, 0, k_xor_ipad, 0, key.length);
System.arraycopy(key, 0, k_xor_opad, 0, key.length);
for (int i = 0; i < BLOCKSIZE; i++)
{
k_xor_ipad[i] ^= 0x36;
k_xor_opad[i] ^= 0x5C;
}
md.update(k_xor_ipad);
}
public final int getDigestLength()
{
return size;
}
public final void update(byte b)
{
md.update(b);
}
public final void update(byte[] b)
{
md.update(b);
}
public final void update(byte[] b, int off, int len)
{
md.update(b, off, len);
}
public final void reset()
{
md.reset();
md.update(k_xor_ipad);
}
public final void digest(byte[] out)
{
digest(out, 0);
}
public final void digest(byte[] out, int off)
{
md.digest(tmp);
md.update(k_xor_opad);
md.update(tmp);
md.digest(tmp);
System.arraycopy(tmp, 0, out, off, size);
md.update(k_xor_ipad);
}
}
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