Chapter 20. The java.security.interfaces Package

As its name implies, the java.security.interfaces package contains only interfaces. These interfaces define methods that provide algorithm-specific information (such as key values and initialization parameter values) about DSA and RSA public and private keys. If you are using the RSA algorithm, for example, and working with a java.security.PublicKey object, you can cast that PublicKey to an RSAPublicKey object and use the RSA-specific methods defined by RSAPublicKey to query the key value directly. Figure 20-1 shows the class hierarchy of this package.

Figure 20-1. The java.security.interfaces package

The java.security.interfaces package was introduced in Java 1.1. In Java 1.2, the java.security.spec package is the preferred way for obtaining algorithm-specific information about keys and algorithm parameters. This package remains useful in Java 1.2, however, for identifying the type of a given PublicKey or PrivateKey object.

The interfaces in this package are typically of interest only to programmers who are implementing a security provider or who want to implement cryptographic algorithms themselves. Use of this package typically requires some familiarity with the mathematics underlying DSA and RSA public-key cryptography.

DSAKey

Java 1.1

java.security.interfaces

PJ1.1(opt)

This interface defines a method that must be implemented by both public and private DSA keys.

public interface DSAKey {
//	Public Instance Methods
	public abstract DSAParams getParams ();
}

Implementations: DSAPrivateKey, DSAPublicKey

DSAKeyPairGenerator

Java 1.1

java.security.interfaces

PJ1.1(opt)

This interface defines algorithm-specific KeyPairGenerator initialization methods for DSA keys. To generate a pair of DSA keys, use the static getInstance() factory method of java.security.KeyPairGenerator and specify "DSA" as the desired algorithm name. If you wish to perform DSA-specific initialization, cast the returned KeyPairGenerator to a DSAKeyPairGenerator and call one of the initialize() methods defined by this interface. Finally, generate the keys by calling generateKeyPair() on the KeyPairGenerator.

public interface DSAKeyPairGenerator {
//	Public Instance Methods
	public abstract void initialize (DSAParams params, java.security.SecureRandom random) throws java.security.InvalidParameterException;
	public abstract void initialize (int modlen, boolean genParams, java.security.SecureRandom random) throws java.security.InvalidParameterException;
}

DSAParams

Java 1.1

java.security.interfaces

PJ1.1(opt)

This interface defines methods for obtaining the DSA parameters g, p, and q. These methods are useful only if you wish to perform cryptographic computation yourself. Using these methods requires a detailed understanding of the mathematics underlying DSA public-key cryptography.

public interface DSAParams {
//	Public Instance Methods
	public abstract java.math.BigInteger getG ();
	public abstract java.math.BigInteger getP ();
	public abstract java.math.BigInteger getQ ();
}

Implementations: java.security.spec.DSAParameterSpec

Passed To: DSAKeyPairGenerator.initialize()

Returned By: DSAKey.getParams()

DSAPrivateKey

Java 1.1

java.security.interfaces

serializable PJ1.1(opt)

This interface represents a DSA private key and provides direct access to the underlying key value. If you are working with a private key you know is a DSA key, you can cast the PrivateKey to a DSAPrivateKey.

public interface DSAPrivateKey extends DSAKey, java.security.PrivateKey {
//	Public Constants
1.2	public static final long serialVersionUID ;	=7776497482533790279
//	Public Instance Methods
	public abstract java.math.BigInteger getX ();
}

Hierarchy: (DSAPrivateKey(DSAKey,java.security.PrivateKey(java.security.Key(Serializable))))

DSAPublicKey

Java 1.1

java.security.interfaces

serializable PJ1.1(opt)

This interface represents a DSA public key and provides direct access to the underlying key value. If you are working with a public key you know is a DSA key, you can cast the PublicKey to a DSAPublicKey.

public interface DSAPublicKey extends DSAKey, java.security.PublicKey {
//	Public Constants
1.2	public static final long serialVersionUID ;	=1234526332779022332
//	Public Instance Methods
	public abstract java.math.BigInteger getY ();
}

Hierarchy: (DSAPublicKey(DSAKey,java.security.PublicKey(java.security.Key(Serializable))))

RSAKey

Java 1.3 Beta

java.security.interfaces

This is a superinterface for RSAPublicKey and RSAPrivateKey; it defines a method shared by both classes. Prior to Java 1.3, the getModulus() method was defined independently by RSAPublicKey and RSAPrivateKey.

public interface RSAKey {
//	Public Instance Methods
	public abstract java.math.BigInteger getModulus ();
}

Implementations: RSAPrivateKey, RSAPublicKey

RSAPrivateCrtKey

Java 1.2

java.security.interfaces

serializable

This interface extends RSAPrivateKey and provides a decomposition (based on the Chinese remainder theorem) of the private-key value into the various pieces that comprise it. This interface is useful only if you plan to implement your own cryptographic algorithms. To use this interface, you must have a detailed understanding of the mathematics underlying RSA public-key cryptography. Given a java.security.PrivateKey object, you can use the instanceof operator to determine whether you can safely cast it to an RSAPrivateCrtKey.

public interface RSAPrivateCrtKey extends RSAPrivateKey {
//	Property Accessor Methods (by property name)
	public abstract java.math.BigInteger getCrtCoefficient ();
	public abstract java.math.BigInteger getPrimeExponentP ();
	public abstract java.math.BigInteger getPrimeExponentQ ();
	public abstract java.math.BigInteger getPrimeP ();
	public abstract java.math.BigInteger getPrimeQ ();
	public abstract java.math.BigInteger getPublicExponent ();
}

Hierarchy: (RSAPrivateCrtKey(RSAPrivateKey(java.security.PrivateKey(java.security.Key(Serializable)),RSAKey)))

RSAPrivateKey

Java 1.2

java.security.interfaces

serializable

This interface represents an RSA private key and provides direct access to the underlying key values. If you are working with a private key you know is an RSA key, you can cast the PrivateKey to an RSAPrivateKey.

public interface RSAPrivateKey extends java.security.PrivateKey, RSAKey {
//	Public Instance Methods
	public abstract java.math.BigInteger getPrivateExponent ();
}

Hierarchy: (RSAPrivateKey(java.security.PrivateKey(java.security.Key(Serializable)),RSAKey))

Implementations: RSAPrivateCrtKey

RSAPublicKey

Java 1.2

java.security.interfaces

serializable

This interface represents an RSA public key and provides direct access to the underlying key values. If you are working with a public key you know is an RSA key, you can cast the PublicKey to an RSAPublicKey.

public interface RSAPublicKey extends java.security.PublicKey, RSAKey {
//	Public Instance Methods
	public abstract java.math.BigInteger getPublicExponent ();
}

Hierarchy: (RSAPublicKey(java.security.PublicKey(java.security.Key(Serializable)),RSAKey))