RC5ParameterSpec.java

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package javax.crypto.spec;

import java.security.spec.AlgorithmParameterSpec;

/**
 * This class specifies the parameters used with the
 * <a href="http://tools.ietf.org/html/rfc2040"><i>RC5</i></a>
 * algorithm.
 *
 * <p> The parameters consist of a version number, a rounds count, a word
 * size, and optionally an initialization vector (IV) (only in feedback mode).
 *
 * <p> This class can be used to initialize a {@code Cipher} object that
 * implements the <i>RC5</i> algorithm as supplied by
 * <a href="http://www.rsa.com">RSA Security LLC</a>,
 * or any parties authorized by RSA Security.
 *
 * @author Jan Luehe
 *
 * @since 1.4
 */
public class RC5ParameterSpec implements AlgorithmParameterSpec {

    private byte[] iv = null;
    private int version;
    private int rounds;
    private int wordSize; // the word size in bits

    /**
     * Constructs a parameter set for RC5 from the given version, number of
     * rounds and word size (in bits).
     *
     * @param version the version.
     * @param rounds the number of rounds.
     * @param wordSize the word size in bits.
     */
    public RC5ParameterSpec(int version, int rounds, int wordSize) {
        this.version = version;
        this.rounds = rounds;
        this.wordSize = wordSize;
    }

    /**
     * Constructs a parameter set for RC5 from the given version, number of
     * rounds, word size (in bits), and IV.
     *
     * <p> Note that the size of the IV (block size) must be twice the word
     * size. The bytes that constitute the IV are those between
     * {@code iv[0]} and {@code iv[2*(wordSize/8)-1]} inclusive.
     *
     * @param version the version.
     * @param rounds the number of rounds.
     * @param wordSize the word size in bits.
     * @param iv the buffer with the IV. The first {@code 2*(wordSize/8)}
     * bytes of the buffer are copied to protect against subsequent
     * modification.
     * @exception IllegalArgumentException if {@code iv} is
     * {@code null} or {@code (iv.length < 2 * (wordSize / 8))}
     */
    public RC5ParameterSpec(int version, int rounds, int wordSize, byte[] iv) {
        this(version, rounds, wordSize, iv, 0);
    }

    /**
     * Constructs a parameter set for RC5 from the given version, number of
     * rounds, word size (in bits), and IV.
     *
     * <p> The IV is taken from {@code iv}, starting at
     * {@code offset} inclusive.
     * Note that the size of the IV (block size), starting at
     * {@code offset} inclusive, must be twice the word size.
     * The bytes that constitute the IV are those between
     * {@code iv[offset]} and {@code iv[offset+2*(wordSize/8)-1]}
     * inclusive.
     *
     * @param version the version.
     * @param rounds the number of rounds.
     * @param wordSize the word size in bits.
     * @param iv the buffer with the IV. The first {@code 2*(wordSize/8)}
     * bytes of the buffer beginning at {@code offset}
     * inclusive are copied to protect against subsequent modification.
     * @param offset the offset in {@code iv} where the IV starts.
     * @exception IllegalArgumentException if {@code iv} is
     * {@code null} or
     * {@code (iv.length - offset < 2 * (wordSize / 8))}
     */
    public RC5ParameterSpec(int version, int rounds, int wordSize,
                            byte[] iv, int offset) {
        this.version = version;
        this.rounds = rounds;
        this.wordSize = wordSize;
        if (iv == null) {
            throw new IllegalArgumentException("IV missing");
        }
        if (offset < 0) {
            throw new ArrayIndexOutOfBoundsException("offset is negative");
        }
        int blockSize = (wordSize / 8) * 2;
        if (iv.length - offset < blockSize) {
            throw new IllegalArgumentException("IV too short");
        }
        this.iv = new byte[blockSize];
        System.arraycopy(iv, offset, this.iv, 0, blockSize);
    }

    /**
     * Returns the version.
     *
     * @return the version.
     */
    public int getVersion() {
        return this.version;
    }

    /**
     * Returns the number of rounds.
     *
     * @return the number of rounds.
     */
    public int getRounds() {
        return this.rounds;
    }

    /**
     * Returns the word size in bits.
     *
     * @return the word size in bits.
     */
    public int getWordSize() {
        return this.wordSize;
    }

    /**
     * Returns the IV or null if this parameter set does not contain an IV.
     *
     * @return the IV or null if this parameter set does not contain an IV.
     * Returns a new array each time this method is called.
     */
    public byte[] getIV() {
        return (iv == null? null:iv.clone());
    }

    /**
     * Tests for equality between the specified object and this
     * object. Two RC5ParameterSpec objects are considered equal if their
     * version numbers, number of rounds, word sizes, and IVs are equal.
     * (Two IV references are considered equal if both are {@code null}.)
     *
     * @param obj the object to test for equality with this object.
     *
     * @return true if the objects are considered equal, false if
     * {@code obj} is null or otherwise.
     */
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof RC5ParameterSpec)) {
            return false;
        }
        RC5ParameterSpec other = (RC5ParameterSpec) obj;

        return ((version == other.version) &&
                (rounds == other.rounds) &&
                (wordSize == other.wordSize) &&
                java.util.Arrays.equals(iv, other.iv));
    }

    /**
     * Calculates a hash code value for the object.
     * Objects that are equal will also have the same hashcode.
     */
    public int hashCode() {
        int retval = 0;
        if (iv != null) {
            for (int i = 1; i < iv.length; i++) {
                retval += iv[i] * i;
            }
        }
        retval += (version + rounds + wordSize);
        return retval;
    }
}