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/*
This file is part of GNUnet.
Copyright (C) 2012, 2013 Christian Grothoff (and other contributing authors)
GNUnet is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; either version 3, or (at your
option) any later version.
GNUnet is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNUnet; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
package org.gnunet.util.crypto;
import org.gnunet.construct.FixedSizeIntegerArray;
import org.gnunet.construct.Message;
import org.gnunet.util.HashCode;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOError;
import java.io.IOException;
import java.math.BigInteger;
import java.security.SecureRandom;
/**
* Private key for elliptic curve DSA.
*/
public class EcdsaPrivateKey implements Message {
/**
* Private key byte string, in big endian form.
*/
@FixedSizeIntegerArray(bitSize = 8, signed = false, length = 32)
public byte[] d;
/**
* Create a private key without allocating the key data.
*/
public EcdsaPrivateKey() {
// empty, needed by org.gnunet.construct.*
}
/**
* Get the anonymous private key. Corresponds to '1'.
*
* @return the anonymous private ECDSA key
*/
public static EcdsaPrivateKey getAnonymous() {
EcdsaPrivateKey privateKey = new EcdsaPrivateKey();
privateKey.d = new byte[32];
privateKey.d[31] = 1;
return privateKey;
}
public EcdsaSignature sign(byte[] data, int purpose) {
return sign(data, purpose, getPublicKey());
}
public EcdsaSignature sign(byte[] data, int purpose, EcdsaPublicKey publicKey) {
ByteArrayOutputStream os = new ByteArrayOutputStream(data.length + 8);
DataOutputStream dos = new DataOutputStream(os);
try {
dos.writeInt(data.length);
dos.writeInt(purpose);
dos.write(data);
} catch (IOException e) {
throw new IOError(e);
}
return signRaw(publicKey, os.toByteArray());
}
/**
* Sign the given data with this private key.
*
* @param data data to signRaw
* @return the signature over both the data and the purpose
*/
public EcdsaSignature signRaw(byte[] data) {
return signRaw(getPublicKey(), data);
}
/**
* Sign the given data with this private key.
*
* @param publicKey public key corresponding to this private key, supplying this parameter
* leads to better performance as the public key does not have to be derived
* @param data data to signRaw
* @return the signature over both the data and the purpose
*/
public EcdsaSignature signRaw(EcdsaPublicKey publicKey, byte[] data) {
EcdsaSignature signature = new EcdsaSignature();
DsaPrng prng = new DsaPrng(d, data);
HashCode h = HashCode.hash(data);
BigInteger z = new BigInteger(1, h.data);
BigInteger dCoeff = this.asCoefficient();
while (true) {
BigInteger k = prng.nextK();
Ed25519 P = Ed25519.B.scalarmult(k);
BigInteger r = P.P0.mod(Ed25519.l);
if (r.equals(BigInteger.ZERO))
continue;
BigInteger kInv = k.modInverse(Ed25519.l);
BigInteger v = z.add(r.multiply(dCoeff));
BigInteger s = kInv.multiply(v).mod(Ed25519.l);
if (s.equals(BigInteger.ZERO))
continue;
signature.r = Ed25519.encodeScalar(r);
signature.s = Ed25519.encodeScalar(s);
return signature;
}
}
/**
* Get the public key for this private key.
*
* @return the public key for this private key
*/
public EcdsaPublicKey getPublicKey() {
Ed25519 A = Ed25519.B.scalarmult(this.asCoefficient());
return new EcdsaPublicKey(A);
}
/**
* Create a randomly generated private ecdsa key.
*
* @return a freshly generated key
*/
public static EcdsaPrivateKey createRandom() {
SecureRandom sr = new SecureRandom();
EcdsaPrivateKey privateKey = new EcdsaPrivateKey();
privateKey.d = new byte[32];
sr.nextBytes(privateKey.d);
return privateKey;
}
public BigInteger asCoefficient() {
return new BigInteger(1, d);
}
/**
* Key that is set to all zeros.
*
* @return key that is set to all zeros
*/
public static EcdsaPrivateKey zeroKey() {
EcdsaPrivateKey pk = new EcdsaPrivateKey();
pk.d = new byte[32];
return pk;
}
}
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