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Java library for Javascript Object Signing and Encryption (JOSE) and JSON Web Tokens (JWT)

There is a newer version: 10.0.1

package com.nimbusds.jose.crypto;


import java.security.Provider;

import net.jcip.annotations.Immutable;

import com.nimbusds.jose.JOSEException;
import com.nimbusds.jose.JWEAlgorithm;


/**
 * Pseudo-Random Function (PRF) parameters, intended for use in the Password-
 * Based Key Derivation Function 2 (PBKDF2).
 *
 * @author Vladimir Dzhuvinov
 * @version 2015-05-26
 */
@Immutable
final class PRFParams {


	/**
	 * The JCA MAC algorithm name.
	 */
	private final String jcaMacAlg;


	/**
	 * The JCA MAC provider, {@code null} to use the default one.
	 */
	private final Provider macProvider;


	/**
	 * The byte length of the key to derive.
	 */
	private final int dkLen;


	/**
	 * Creates a new pseudo-random function parameters instance.
	 *
	 * @param jcaMacAlg   The JCA MAC algorithm name. Must not be
	 *                    {@code null}.
	 * @param macProvider The JCA MAC provider, {@code null} to use the
	 *                    default one.
	 * @param dkLen       The byte length of the key to derive.

	 */
	public PRFParams(String jcaMacAlg, Provider macProvider, int dkLen) {
		this.jcaMacAlg = jcaMacAlg;
		this.macProvider = macProvider;
		this.dkLen = dkLen;
	}


	/**
	 * Returns the JCA MAC algorithm name.
	 *
	 * @return The JCA MAC algorithm name.
	 */
	public String getMACAlgorithm() {

		return jcaMacAlg;
	}


	/**
	 * Returns the JCA MAC provider.
	 *
	 * @return The JCA MAC provider, {@code null} to use the default one.
	 */
	public Provider getMacProvider() {

		return macProvider;
	}


	/**
	 * Returns the byte length of the key to derive.
	 *
	 * @return The byte length of the key to derive.
	 */
	public int getDerivedKeyByteLength() {

		return dkLen;
	}


	/**
	 * Resolves the Pseudo-Random Function (PRF) parameters for the
	 * specified PBES2 JWE algorithm.
	 *
	 * @param alg         The JWE algorithm. Must be supported and not
	 *                    {@code null}.
	 * @param macProvider The specific MAC JCA provider, {@code null} to
	 *                    use the default one.
	 *
	 * @return The PRF parameters.
	 *
	 * @throws JOSEException If the JWE algorithm is not supported.
	 */
	public static PRFParams resolve(final JWEAlgorithm alg,
					   final Provider macProvider)
		throws JOSEException {

		final String jcaMagAlg;
		final int dkLen;

		if (JWEAlgorithm.PBES2_HS256_A128KW.equals(alg)) {
			jcaMagAlg = "HmacSHA256";
			dkLen = 16;
		} else if (JWEAlgorithm.PBES2_HS384_A192KW.equals(alg)) {
			jcaMagAlg = "HmacSHA384";
			dkLen = 24;
		} else if (JWEAlgorithm.PBES2_HS512_A256KW.equals(alg)) {
			jcaMagAlg = "HmacSHA512";
			dkLen = 32;
		} else {
			throw new JOSEException(AlgorithmSupportMessage.unsupportedJWEAlgorithm(
				alg,
				PasswordBasedCryptoProvider.SUPPORTED_ALGORITHMS));
		}

		return new PRFParams(jcaMagAlg, macProvider, dkLen);
	}
}