DESKeySpec.java

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package javax.crypto.spec;

import java.security.InvalidKeyException;

/**
 * This class specifies a DES key.
 *
 * @author Jan Luehe
 *
 * @since 1.4
 */
public class DESKeySpec implements java.security.spec.KeySpec {

    /**
     * The constant which defines the length of a DES key in bytes.
     */
    public static final int DES_KEY_LEN = 8;

    private byte[] key;

    /*
     * Weak/semi-weak keys copied from FIPS 74.
     *
     * "...The first 6 keys have duals different than themselves, hence
     * each is both a key and a dual giving 12 keys with duals. The last
     * four keys equal their duals, and are called self-dual keys..."
     *
     * 1.   E001E001F101F101    01E001E001F101F1
     * 2.   FE1FFE1FFEOEFEOE    1FFE1FFEOEFEOEFE
     * 3.   E01FE01FF10EF10E    1FE01FEOOEF10EF1
     * 4.   01FE01FE01FE01FE    FE01FE01FE01FE01
     * 5.   011F011F010E010E    1F011F010E010E01
     * 6.   E0FEE0FEF1FEF1FE    FEE0FEE0FEF1FEF1
     * 7.   0101010101010101    0101010101010101
     * 8.   FEFEFEFEFEFEFEFE    FEFEFEFEFEFEFEFE
     * 9.   E0E0E0E0F1F1F1F1    E0E0E0E0F1F1F1F1
     * 10.  1F1F1F1F0E0E0E0E    1F1F1F1F0E0E0E0E
     */
    private static final byte[][] WEAK_KEYS = {

        { (byte)0x01, (byte)0x01, (byte)0x01, (byte)0x01, (byte)0x01,
          (byte)0x01, (byte)0x01, (byte)0x01 },

        { (byte)0xFE, (byte)0xFE, (byte)0xFE, (byte)0xFE, (byte)0xFE,
          (byte)0xFE, (byte)0xFE, (byte)0xFE },

        { (byte)0x1F, (byte)0x1F, (byte)0x1F, (byte)0x1F, (byte)0x0E,
          (byte)0x0E, (byte)0x0E, (byte)0x0E },

        { (byte)0xE0, (byte)0xE0, (byte)0xE0, (byte)0xE0, (byte)0xF1,
          (byte)0xF1, (byte)0xF1, (byte)0xF1 },

        { (byte)0x01, (byte)0xFE, (byte)0x01, (byte)0xFE, (byte)0x01,
          (byte)0xFE, (byte)0x01, (byte)0xFE },

        { (byte)0x1F, (byte)0xE0, (byte)0x1F, (byte)0xE0, (byte)0x0E,
          (byte)0xF1, (byte)0x0E, (byte)0xF1 },

        { (byte)0x01, (byte)0xE0, (byte)0x01, (byte)0xE0, (byte)0x01,
          (byte)0xF1, (byte)0x01, (byte)0xF1 },

        { (byte)0x1F, (byte)0xFE, (byte)0x1F, (byte)0xFE, (byte)0x0E,
          (byte)0xFE, (byte)0x0E, (byte)0xFE },

        { (byte)0x01, (byte)0x1F, (byte)0x01, (byte)0x1F, (byte)0x01,
          (byte)0x0E, (byte)0x01, (byte)0x0E },

        { (byte)0xE0, (byte)0xFE, (byte)0xE0, (byte)0xFE, (byte)0xF1,
          (byte)0xFE, (byte)0xF1, (byte)0xFE },

        { (byte)0xFE, (byte)0x01, (byte)0xFE, (byte)0x01, (byte)0xFE,
          (byte)0x01, (byte)0xFE, (byte)0x01 },

        { (byte)0xE0, (byte)0x1F, (byte)0xE0, (byte)0x1F, (byte)0xF1,
          (byte)0x0E, (byte)0xF1, (byte)0x0E },

        { (byte)0xE0, (byte)0x01, (byte)0xE0, (byte)0x01, (byte)0xF1,
          (byte)0x01, (byte)0xF1, (byte)0x01 },

        { (byte)0xFE, (byte)0x1F, (byte)0xFE, (byte)0x1F, (byte)0xFE,
          (byte)0x0E, (byte)0xFE, (byte)0x0E },

        { (byte)0x1F, (byte)0x01, (byte)0x1F, (byte)0x01, (byte)0x0E,
          (byte)0x01, (byte)0x0E, (byte)0x01 },

        { (byte)0xFE, (byte)0xE0, (byte)0xFE, (byte)0xE0, (byte)0xFE,
          (byte)0xF1, (byte)0xFE, (byte)0xF1 }
    };

    /**
     * Creates a DESKeySpec object using the first 8 bytes in
     * <code>key</code> as the key material for the DES key.
     *
     * <p> The bytes that constitute the DES key are those between
     * <code>key[0]</code> and <code>key[7]</code> inclusive.
     *
     * @param key the buffer with the DES key material. The first 8 bytes
     * of the buffer are copied to protect against subsequent modification.
     *
     * @exception NullPointerException if the given key material is
     * <code>null</code>
     * @exception InvalidKeyException if the given key material is shorter
     * than 8 bytes.
     */
    public DESKeySpec(byte[] key) throws InvalidKeyException {
        this(key, 0);
    }

    /**
     * Creates a DESKeySpec object using the first 8 bytes in
     * <code>key</code>, beginning at <code>offset</code> inclusive,
     * as the key material for the DES key.
     *
     * <p> The bytes that constitute the DES key are those between
     * <code>key[offset]</code> and <code>key[offset+7]</code> inclusive.
     *
     * @param key the buffer with the DES key material. The first 8 bytes
     * of the buffer beginning at <code>offset</code> inclusive are copied
     * to protect against subsequent modification.
     * @param offset the offset in <code>key</code>, where the DES key
     * material starts.
     *
     * @exception NullPointerException if the given key material is
     * <code>null</code>
     * @exception InvalidKeyException if the given key material, starting at
     * <code>offset</code> inclusive, is shorter than 8 bytes.
     */
    public DESKeySpec(byte[] key, int offset) throws InvalidKeyException {
        if (key.length - offset < DES_KEY_LEN) {
            throw new InvalidKeyException("Wrong key size");
        }
        this.key = new byte[DES_KEY_LEN];
        System.arraycopy(key, offset, this.key, 0, DES_KEY_LEN);
    }

    /**
     * Returns the DES key material.
     *
     * @return the DES key material. Returns a new array
     * each time this method is called.
     */
    public byte[] getKey() {
        return this.key.clone();
    }

    /**
     * Checks if the given DES key material, starting at <code>offset</code>
     * inclusive, is parity-adjusted.
     *
     * @param key the buffer with the DES key material.
     * @param offset the offset in <code>key</code>, where the DES key
     * material starts.
     *
     * @return true if the given DES key material is parity-adjusted, false
     * otherwise.
     *
     * @exception InvalidKeyException if the given key material is
     * <code>null</code>, or starting at <code>offset</code> inclusive, is
     * shorter than 8 bytes.
     */
    public static boolean isParityAdjusted(byte[] key, int offset)
        throws InvalidKeyException {
            if (key == null) {
                throw new InvalidKeyException("null key");
            }
            if (key.length - offset < DES_KEY_LEN) {
                throw new InvalidKeyException("Wrong key size");
            }

            for (int i = 0; i < DES_KEY_LEN; i++) {
                int k = Integer.bitCount(key[offset++] & 0xff);
                if ((k & 1) == 0) {
                    return false;
                }
            }

            return true;
    }

    /**
     * Checks if the given DES key material is weak or semi-weak.
     *
     * @param key the buffer with the DES key material.
     * @param offset the offset in <code>key</code>, where the DES key
     * material starts.
     *
     * @return true if the given DES key material is weak or semi-weak, false
     * otherwise.
     *
     * @exception InvalidKeyException if the given key material is
     * <code>null</code>, or starting at <code>offset</code> inclusive, is
     * shorter than 8 bytes.
     */
    public static boolean isWeak(byte[] key, int offset)
        throws InvalidKeyException {
        if (key == null) {
            throw new InvalidKeyException("null key");
        }
        if (key.length - offset < DES_KEY_LEN) {
            throw new InvalidKeyException("Wrong key size");
        }
        for (int i = 0; i < WEAK_KEYS.length; i++) {
            boolean found = true;
            for (int j = 0; j < DES_KEY_LEN && found == true; j++) {
                if (WEAK_KEYS[i][j] != key[j+offset]) {
                    found = false;
                }
            }
            if (found == true) {
                return found;
            }
        }
        return false;
    }
}