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package org.spongycastle.crypto.generators;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.Digest;
import org.spongycastle.crypto.PBEParametersGenerator;
import org.spongycastle.crypto.params.KeyParameter;
import org.spongycastle.crypto.params.ParametersWithIV;
/**
* Generator for PBE derived keys and ivs as defined by PKCS 5 V2.0 Scheme 1.
* Note this generator is limited to the size of the hash produced by the
* digest used to drive it.
* <p>
* The document this implementation is based on can be found at
* <a href=http://www.rsasecurity.com/rsalabs/pkcs/pkcs-5/index.html>
* RSA's PKCS5 Page</a>
*/
public class PKCS5S1ParametersGenerator
extends PBEParametersGenerator
{
private Digest digest;
/**
* Construct a PKCS 5 Scheme 1 Parameters generator.
*
* @param digest the digest to be used as the source of derived keys.
*/
public PKCS5S1ParametersGenerator(
Digest digest)
{
this.digest = digest;
}
/**
* the derived key function, the ith hash of the password and the salt.
*/
private byte[] generateDerivedKey()
{
byte[] digestBytes = new byte[digest.getDigestSize()];
digest.update(password, 0, password.length);
digest.update(salt, 0, salt.length);
digest.doFinal(digestBytes, 0);
for (int i = 1; i < iterationCount; i++)
{
digest.update(digestBytes, 0, digestBytes.length);
digest.doFinal(digestBytes, 0);
}
return digestBytes;
}
/**
* Generate a key parameter derived from the password, salt, and iteration
* count we are currently initialised with.
*
* @param keySize the size of the key we want (in bits)
* @return a KeyParameter object.
* @exception IllegalArgumentException if the key length larger than the base hash size.
*/
public CipherParameters generateDerivedParameters(
int keySize)
{
keySize = keySize / 8;
if (keySize > digest.getDigestSize())
{
throw new IllegalArgumentException(
"Can't generate a derived key " + keySize + " bytes long.");
}
byte[] dKey = generateDerivedKey();
return new KeyParameter(dKey, 0, keySize);
}
/**
* Generate a key with initialisation vector parameter derived from
* the password, salt, and iteration count we are currently initialised
* with.
*
* @param keySize the size of the key we want (in bits)
* @param ivSize the size of the iv we want (in bits)
* @return a ParametersWithIV object.
* @exception IllegalArgumentException if keySize + ivSize is larger than the base hash size.
*/
public CipherParameters generateDerivedParameters(
int keySize,
int ivSize)
{
keySize = keySize / 8;
ivSize = ivSize / 8;
if ((keySize + ivSize) > digest.getDigestSize())
{
throw new IllegalArgumentException(
"Can't generate a derived key " + (keySize + ivSize) + " bytes long.");
}
byte[] dKey = generateDerivedKey();
return new ParametersWithIV(new KeyParameter(dKey, 0, keySize), dKey, keySize, ivSize);
}
/**
* Generate a key parameter for use with a MAC derived from the password,
* salt, and iteration count we are currently initialised with.
*
* @param keySize the size of the key we want (in bits)
* @return a KeyParameter object.
* @exception IllegalArgumentException if the key length larger than the base hash size.
*/
public CipherParameters generateDerivedMacParameters(
int keySize)
{
return generateDerivedParameters(keySize);
}
}
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