package gnu.crypto.sig.rsa;
// ----------------------------------------------------------------------------
// $Id: RSAPKCS1V1_5Signature.java,v 1.3 2005/10/06 04:24:18 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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 2, or (at your option)
// any later version.
//
// GNU Crypto 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 this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
// 51 Franklin Street, Fifth Floor,
// Boston, MA 02110-1301
// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
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// library, you may extend this exception to your version of the
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// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
import gnu.crypto.Registry;
import gnu.crypto.hash.HashFactory;
import gnu.crypto.hash.IMessageDigest;
import gnu.crypto.sig.BaseSignature;
import java.math.BigInteger;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.util.Arrays;
/**
* <p>The RSA-PKCS1-V1.5 signature scheme is a digital signature scheme with
* appendix (SSA) combining the RSA algorithm with the EMSA-PKCS1-v1_5 encoding
* method.</p>
*
* <p>References:</p>
* <ol>
* <li><a href="http://www.cosic.esat.kuleuven.ac.be/nessie/workshop/submissions/rsa-pss.zip">
* RSA-PSS Signature Scheme with Appendix, part B.</a><br>
* Primitive specification and supporting documentation.<br>
* Jakob Jonsson and Burt Kaliski.</li>
*
* <li><a href="http://www.ietf.org/rfc/rfc3447.txt">Public-Key Cryptography
* Standards (PKCS) #1:</a><br>
* RSA Cryptography Specifications Version 2.1.<br>
* Jakob Jonsson and Burt Kaliski.</li>
* </ol>
*
* @version $Revision: 1.3 $
*/
public class RSAPKCS1V1_5Signature extends BaseSignature {
// Constants and variables
// -------------------------------------------------------------------------
/** The underlying EMSA-PKCS1-v1.5 instance for this object. */
private EMSA_PKCS1_V1_5 pkcs1;
// Constructor(s)
// -------------------------------------------------------------------------
/**
* Default 0-arguments constructor. Uses SHA-1 as the default hash.
*/
public RSAPKCS1V1_5Signature() {
this(Registry.SHA160_HASH);
}
/**
* <p>Constructs an instance of this object using the designated message
* digest algorithm as its underlying hash function.</p>
*
* @param mdName the canonical name of the underlying hash function.
*/
public RSAPKCS1V1_5Signature(final String mdName) {
super(Registry.RSA_PKCS1_V1_5_SIG, HashFactory.getInstance(mdName));
pkcs1 = EMSA_PKCS1_V1_5.getInstance(mdName);
}
/** Private constructor for cloning purposes. */
private RSAPKCS1V1_5Signature(final RSAPKCS1V1_5Signature that) {
this(that.md.name());
this.publicKey = that.publicKey;
this.privateKey = that.privateKey;
this.md = (IMessageDigest) that.md.clone();
this.pkcs1 = (EMSA_PKCS1_V1_5) that.pkcs1.clone();
}
// Class methods
// -------------------------------------------------------------------------
// Instance methods
// -------------------------------------------------------------------------
// Implementation of abstract methods in superclass ------------------------
public Object clone() {
return new RSAPKCS1V1_5Signature(this);
}
protected void setupForVerification(final PublicKey k)
throws IllegalArgumentException {
if (!(k instanceof RSAPublicKey)) {
throw new IllegalArgumentException();
}
publicKey = k;
}
protected void setupForSigning(final PrivateKey k)
throws IllegalArgumentException {
if (!(k instanceof RSAPrivateKey)) {
throw new IllegalArgumentException();
}
privateKey = k;
}
protected Object generateSignature() throws IllegalStateException {
// 1. EMSA-PKCS1-v1_5 encoding: Apply the EMSA-PKCS1-v1_5 encoding
// operation (Section 9.2) to the message M to produce an encoded
// message EM of length k octets:
//
// EM = EMSA-PKCS1-V1_5-ENCODE (M, k).
//
// If the encoding operation outputs "message too long," output
// "message too long" and stop. If the encoding operation outputs
// "intended encoded message length too short," output "RSA modulus
// too short" and stop.
final int modBits = ((RSAPrivateKey) privateKey).getModulus().bitLength();
final int k = (modBits + 7) / 8;
final byte[] EM = pkcs1.encode(md.digest(), k);
// 2. RSA signature:
// a. Convert the encoded message EM to an integer message epresentative
// m (see Section 4.2): m = OS2IP (EM).
final BigInteger m = new BigInteger(1, EM);
// b. Apply the RSASP1 signature primitive (Section 5.2.1) to the RSA
// private key K and the message representative m to produce an
// integer signature representative s: s = RSASP1 (K, m).
final BigInteger s = RSA.sign(privateKey, m);
// c. Convert the signature representative s to a signature S of length
// k octets (see Section 4.1): S = I2OSP (s, k).
// 3. Output the signature S.
return RSA.I2OSP(s, k);
}
protected boolean verifySignature(final Object sig) throws IllegalStateException {
if (publicKey == null) {
throw new IllegalStateException();
}
final byte[] S = (byte[]) sig;
// 1. Length checking: If the length of the signature S is not k octets,
// output "invalid signature" and stop.
final int modBits = ((RSAPublicKey) publicKey).getModulus().bitLength();
final int k = (modBits + 7) / 8;
if (S.length != k) {
return false;
}
// 2. RSA verification:
// a. Convert the signature S to an integer signature representative
// s (see Section 4.2): s = OS2IP (S).
final BigInteger s = new BigInteger(1, S);
// b. Apply the RSAVP1 verification primitive (Section 5.2.2) to the
// RSA public key (n, e) and the signature representative s to
// produce an integer message representative m:
// m = RSAVP1 ((n, e), s).
// If RSAVP1 outputs "signature representative out of range,"
// output "invalid signature" and stop.
final BigInteger m;
try {
m = RSA.verify(publicKey, s);
} catch (IllegalArgumentException x) {
return false;
}
// c. Convert the message representative m to an encoded message EM
// of length k octets (see Section 4.1): EM = I2OSP (m, k).
// If I2OSP outputs "integer too large," output "invalid signature"
// and stop.
final byte[] EM;
try {
EM = RSA.I2OSP(m, k);
} catch (IllegalArgumentException x) {
return false;
}
// 3. EMSA-PKCS1-v1_5 encoding: Apply the EMSA-PKCS1-v1_5 encoding
// operation (Section 9.2) to the message M to produce a second
// encoded message EM' of length k octets:
// EM' = EMSA-PKCS1-V1_5-ENCODE (M, k).
// If the encoding operation outputs "message too long," output
// "message too long" and stop. If the encoding operation outputs
// "intended encoded message length too short," output "RSA modulus
// too short" and stop.
final byte[] EMp = pkcs1.encode(md.digest(), k);
// 4. Compare the encoded message EM and the second encoded message EM'.
// If they are the same, output "valid signature"; otherwise, output
// "invalid signature."
return Arrays.equals(EM, EMp);
}
}