import sun.security.x509.AlgIdDSA; //导入依赖的package包/类
/**
 * Make a DSA public key out of a public key and three parameters.
 * The p, q, and g parameters may be null, but if so, parameters will need
 * to be supplied from some other source before this key can be used in
 * cryptographic operations.  PKIX RFC2459bis explicitly allows DSA public
 * keys without parameters, where the parameters are provided in the
 * issuer's DSA public key.
 *
 * @param y the actual key bits
 * @param p DSA parameter p, may be null if all of p, q, and g are null.
 * @param q DSA parameter q, may be null if all of p, q, and g are null.
 * @param g DSA parameter g, may be null if all of p, q, and g are null.
 */
public DSAPublicKey(BigInteger y, BigInteger p, BigInteger q,
                    BigInteger g)
throws InvalidKeyException {
    this.y = y;
    algid = new AlgIdDSA(p, q, g);

    try {
        byte[] keyArray = new DerValue(DerValue.tag_Integer,
                           y.toByteArray()).toByteArray();
        setKey(new BitArray(keyArray.length*8, keyArray));
        encode();
    } catch (IOException e) {
        throw new InvalidKeyException("could not DER encode y: " +
                                      e.getMessage());
    }
}
 

import sun.security.x509.AlgIdDSA; //导入依赖的package包/类
/**
 * Make a DSA private key out of a private key and three parameters.
 */
public DSAPrivateKey(BigInteger x, BigInteger p,
                     BigInteger q, BigInteger g)
throws InvalidKeyException {
    this.x = x;
    algid = new AlgIdDSA(p, q, g);

    try {
        key = new DerValue(DerValue.tag_Integer,
                           x.toByteArray()).toByteArray();
        encode();
    } catch (IOException e) {
        InvalidKeyException ike = new InvalidKeyException(
            "could not DER encode x: " + e.getMessage());
        ike.initCause(e);
        throw ike;
    }
}
 

import sun.security.x509.AlgIdDSA; //导入依赖的package包/类
/**
 * Make a DSA public key out of a public key and three parameters.
 * The p, q, and g parameters may be null, but if so, parameters will need
 * to be supplied from some other source before this key can be used in
 * cryptographic operations.  PKIX RFC2459bis explicitly allows DSA public
 * keys without parameters, where the parameters are provided in the
 * issuer's DSA public key.
 *
 * @param y the actual key bits
 * @param p DSA parameter p, may be null if all of p, q, and g are null.
 * @param q DSA parameter q, may be null if all of p, q, and g are null.
 * @param g DSA parameter g, may be null if all of p, q, and g are null.
 */
public DSAPublicKey(BigInteger y, BigInteger p, BigInteger q,
                    BigInteger g)
throws InvalidKeyException {
    this.y = y;
    algid = new AlgIdDSA(p, q, g);

    try {
        key = new DerValue(DerValue.tag_Integer,
                           y.toByteArray()).toByteArray();
        encode();
    } catch (IOException e) {
        throw new InvalidKeyException("could not DER encode y: " +
                                      e.getMessage());
    }
}