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package javax.crypto.spec;

import java.math.BigInteger;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.MGF1ParameterSpec;

/**
 * This class specifies the set of parameters used with OAEP Padding,
 * as defined in the
 * <a href="https://tools.ietf.org/rfc/rfc8017.txt">PKCS#1 v2.2</a> standard.
 *
 * Its ASN.1 definition in PKCS#1 standard is described below:
 * <pre>
 * RSAES-OAEP-params ::= SEQUENCE {
 *   hashAlgorithm      [0] HashAlgorithm     DEFAULT sha1,
 *   maskGenAlgorithm   [1] MaskGenAlgorithm  DEFAULT mgf1SHA1,
 *   pSourceAlgorithm   [2] PSourceAlgorithm  DEFAULT pSpecifiedEmpty
 * }
 * </pre>
 * where
 * <pre>
 * HashAlgorithm ::= AlgorithmIdentifier {
 *   {OAEP-PSSDigestAlgorithms}
 * }
 * MaskGenAlgorithm ::= AlgorithmIdentifier { {PKCS1MGFAlgorithms} }
 * PSourceAlgorithm ::= AlgorithmIdentifier {
 *   {PKCS1PSourceAlgorithms}
 * }
 *
 * OAEP-PSSDigestAlgorithms    ALGORITHM-IDENTIFIER ::= {
 *   { OID id-sha1       PARAMETERS NULL }|
 *   { OID id-sha224     PARAMETERS NULL }|
 *   { OID id-sha256     PARAMETERS NULL }|
 *   { OID id-sha384     PARAMETERS NULL }|
 *   { OID id-sha512     PARAMETERS NULL }|
 *   { OID id-sha512-224 PARAMETERS NULL }|
 *   { OID id-sha512-256 PARAMETERS NULL },
 *   ...  -- Allows for future expansion --
 * }
 * PKCS1MGFAlgorithms    ALGORITHM-IDENTIFIER ::= {
 *   { OID id-mgf1 PARAMETERS HashAlgorithm },
 *   ...  -- Allows for future expansion --
 * }
 * PKCS1PSourceAlgorithms    ALGORITHM-IDENTIFIER ::= {
 *   { OID id-pSpecified PARAMETERS EncodingParameters },
 *   ...  -- Allows for future expansion --
 * }
 * EncodingParameters ::= OCTET STRING(SIZE(0..MAX))
 * </pre>
 * <p>Note: the OAEPParameterSpec.DEFAULT uses the following:
 * <pre>
 *     message digest  -- "SHA-1"
 *     mask generation function (mgf) -- "MGF1"
 *     parameters for mgf -- MGF1ParameterSpec.SHA1
 *     source of encoding input -- PSource.PSpecified.DEFAULT
 * </pre>
 *
 * @see java.security.spec.MGF1ParameterSpec
 * @see PSource
 *
 * @author Valerie Peng
 *
 * @since 1.5
 */
public class OAEPParameterSpec implements AlgorithmParameterSpec {

    private String mdName = "SHA-1";
    private String mgfName = "MGF1";
    private AlgorithmParameterSpec mgfSpec = MGF1ParameterSpec.SHA1;
    private PSource pSrc = PSource.PSpecified.DEFAULT;

    /**
     * The OAEP parameter set with all default values.
     */
    public static final OAEPParameterSpec DEFAULT = new OAEPParameterSpec();

    /**
     * Constructs a parameter set for OAEP padding as defined in
     * the PKCS #1 standard using the default values.
     */
    private OAEPParameterSpec() {
    }

    /**
     * Constructs a parameter set for OAEP padding as defined in
     * the PKCS #1 standard using the specified message digest
     * algorithm <code>mdName</code>, mask generation function
     * algorithm <code>mgfName</code>, parameters for the mask
     * generation function <code>mgfSpec</code>, and source of
     * the encoding input P <code>pSrc</code>.
     *
     * @param mdName the algorithm name for the message digest.
     * @param mgfName the algorithm name for the mask generation
     * function.
     * @param mgfSpec the parameters for the mask generation function.
     * If null is specified, null will be returned by getMGFParameters().
     * @param pSrc the source of the encoding input P.
     * @exception NullPointerException if <code>mdName</code>,
     * <code>mgfName</code>, or <code>pSrc</code> is null.
     */
    public OAEPParameterSpec(String mdName, String mgfName,
                             AlgorithmParameterSpec mgfSpec,
                             PSource pSrc) {
        if (mdName == null) {
            throw new NullPointerException("digest algorithm is null");
        }
        if (mgfName == null) {
            throw new NullPointerException("mask generation function " +
                                           "algorithm is null");
        }
        if (pSrc == null) {
            throw new NullPointerException("source of the encoding input " +
                                           "is null");
        }
        this.mdName =  mdName;
        this.mgfName =  mgfName;
        this.mgfSpec =  mgfSpec;
        this.pSrc =  pSrc;
    }

    /**
     * Returns the message digest algorithm name.
     *
     * @return the message digest algorithm name.
     */
    public String getDigestAlgorithm() {
        return mdName;
    }

    /**
     * Returns the mask generation function algorithm name.
     *
     * @return the mask generation function algorithm name.
     */
    public String getMGFAlgorithm() {
        return mgfName;
    }

    /**
     * Returns the parameters for the mask generation function.
     *
     * @return the parameters for the mask generation function.
     */
    public AlgorithmParameterSpec getMGFParameters() {
        return mgfSpec;
    }

    /**
     * Returns the source of encoding input P.
     *
     * @return the source of encoding input P.
     */
    public PSource getPSource() {
        return pSrc;
    }
}