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package sun.security.provider;

import java.math.BigInteger;

import java.security.*;
import java.security.SecureRandom;
import java.security.interfaces.DSAParams;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidParameterSpecException;
import java.security.spec.DSAParameterSpec;

import sun.security.jca.JCAUtil;
import static sun.security.util.SecurityProviderConstants.DEF_DSA_KEY_SIZE;
import static sun.security.util.SecurityProviderConstants.getDefDSASubprimeSize;

This class generates DSA key parameters and public/private key pairs according to the DSS standard NIST FIPS 186. It uses the updated version of SHA, SHA-1 as described in FIPS 180-1.
Author:Benjamin Renaud, Andreas Sterbenz
/** * This class generates DSA key parameters and public/private key * pairs according to the DSS standard NIST FIPS 186. It uses the * updated version of SHA, SHA-1 as described in FIPS 180-1. * * @author Benjamin Renaud * @author Andreas Sterbenz * */
class DSAKeyPairGenerator extends KeyPairGenerator { /* Length for prime P and subPrime Q in bits */ private int plen; private int qlen; /* whether to force new parameters to be generated for each KeyPair */ boolean forceNewParameters; /* preset algorithm parameters. */ private DSAParameterSpec params; /* The source of random bits to use */ private SecureRandom random; DSAKeyPairGenerator(int defaultKeySize) { super("DSA"); initialize(defaultKeySize, null); } private static void checkStrength(int sizeP, int sizeQ) { if ((sizeP >= 512) && (sizeP <= 1024) && (sizeP % 64 == 0) && sizeQ == 160) { // traditional - allow for backward compatibility // L=multiples of 64 and between 512 and 1024 (inclusive) // N=160 } else if (sizeP == 2048 && (sizeQ == 224 || sizeQ == 256)) { // L=2048, N=224 or 256 } else if (sizeP == 3072 && sizeQ == 256) { // L=3072, N=256 } else { throw new InvalidParameterException ("Unsupported prime and subprime size combination: " + sizeP + ", " + sizeQ); } } public void initialize(int modlen, SecureRandom random) { init(modlen, random, false); }
Initializes the DSA object using a parameter object.
Params:
  • params – the parameter set to be used to generate the keys.
  • random – the source of randomness for this generator.
Throws:
/** * Initializes the DSA object using a parameter object. * * @param params the parameter set to be used to generate * the keys. * @param random the source of randomness for this generator. * * @exception InvalidAlgorithmParameterException if the given parameters * are inappropriate for this key pair generator */
public void initialize(AlgorithmParameterSpec params, SecureRandom random) throws InvalidAlgorithmParameterException { if (!(params instanceof DSAParameterSpec)) { throw new InvalidAlgorithmParameterException ("Inappropriate parameter"); } init((DSAParameterSpec)params, random, false); } void init(int modlen, SecureRandom random, boolean forceNew) { int subPrimeLen = getDefDSASubprimeSize(modlen); checkStrength(modlen, subPrimeLen); this.plen = modlen; this.qlen = subPrimeLen; this.params = null; this.random = random; this.forceNewParameters = forceNew; } void init(DSAParameterSpec params, SecureRandom random, boolean forceNew) { int sizeP = params.getP().bitLength(); int sizeQ = params.getQ().bitLength(); checkStrength(sizeP, sizeQ); this.plen = sizeP; this.qlen = sizeQ; this.params = params; this.random = random; this.forceNewParameters = forceNew; }
Generates a pair of keys usable by any JavaSecurity compliant DSA implementation.
/** * Generates a pair of keys usable by any JavaSecurity compliant * DSA implementation. */
public KeyPair generateKeyPair() { if (random == null) { random = JCAUtil.getSecureRandom(); } DSAParameterSpec spec; try { if (forceNewParameters) { // generate new parameters each time spec = ParameterCache.getNewDSAParameterSpec(plen, qlen, random); } else { if (params == null) { params = ParameterCache.getDSAParameterSpec(plen, qlen, random); } spec = params; } } catch (GeneralSecurityException e) { throw new ProviderException(e); } return generateKeyPair(spec.getP(), spec.getQ(), spec.getG(), random); } private KeyPair generateKeyPair(BigInteger p, BigInteger q, BigInteger g, SecureRandom random) { BigInteger x = generateX(random, q); BigInteger y = generateY(x, p, g); try { // See the comments in DSAKeyFactory, 4532506, and 6232513. DSAPublicKey pub; pub = new DSAPublicKeyImpl(y, p, q, g); DSAPrivateKey priv = new DSAPrivateKey(x, p, q, g); KeyPair pair = new KeyPair(pub, priv); return pair; } catch (InvalidKeyException e) { throw new ProviderException(e); } }
Generate the private key component of the key pair using the provided source of random bits. This method uses the random but source passed to generate a seed and then calls the seed-based generateX method.
/** * Generate the private key component of the key pair using the * provided source of random bits. This method uses the random but * source passed to generate a seed and then calls the seed-based * generateX method. */
private BigInteger generateX(SecureRandom random, BigInteger q) { BigInteger x = null; byte[] temp = new byte[qlen]; while (true) { random.nextBytes(temp); x = new BigInteger(1, temp).mod(q); if (x.signum() > 0 && (x.compareTo(q) < 0)) { return x; } } }
Generate the public key component y of the key pair.
Params:
  • x – the private key component.
  • p – the base parameter.
/** * Generate the public key component y of the key pair. * * @param x the private key component. * * @param p the base parameter. */
BigInteger generateY(BigInteger x, BigInteger p, BigInteger g) { BigInteger y = g.modPow(x, p); return y; } public static final class Current extends DSAKeyPairGenerator { public Current() { super(DEF_DSA_KEY_SIZE); } } public static final class Legacy extends DSAKeyPairGenerator implements java.security.interfaces.DSAKeyPairGenerator { public Legacy() { super(1024); }
Initializes the DSA key pair generator. If genParams is false, a set of pre-computed parameters is used.
/** * Initializes the DSA key pair generator. If <code>genParams</code> * is false, a set of pre-computed parameters is used. */
@Override public void initialize(int modlen, boolean genParams, SecureRandom random) throws InvalidParameterException { if (genParams) { super.init(modlen, random, true); } else { DSAParameterSpec cachedParams = ParameterCache.getCachedDSAParameterSpec(modlen, getDefDSASubprimeSize(modlen)); if (cachedParams == null) { throw new InvalidParameterException ("No precomputed parameters for requested modulus" + " size available"); } super.init(cachedParams, random, false); } }
Initializes the DSA object using a DSA parameter object.
Params:
  • params – a fully initialized DSA parameter object.
/** * Initializes the DSA object using a DSA parameter object. * * @param params a fully initialized DSA parameter object. */
@Override public void initialize(DSAParams params, SecureRandom random) throws InvalidParameterException { if (params == null) { throw new InvalidParameterException("Params must not be null"); } DSAParameterSpec spec = new DSAParameterSpec (params.getP(), params.getQ(), params.getG()); super.init(spec, random, false); } } }