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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

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package com.sun.crypto.provider;

import java.security.InvalidKeyException;

/**

 * Implementation of the RC2(tm) algorithm as described in RFC 2268.

 *

 * RC2 is a 16-bit based algorithm and not particularly fast on 32/64 bit

 * architectures. Also, note that although the JVM has a 16-bit integer

 * type (short), all expressions are evaluated either in 32 or 64 bit

 * (int or long). Expression such as "s1 = s2 + s3" are implemented by

 * first promoting s2 and s3 to int, performing an int addition, and

 * then demoting the result back to short to store in s1. To avoid this

 * fairly slow process, we use the int type throughout and manually insert

 * "& 0xffff" where necessary.

 *

 * @since   1.5

 * @author  Andreas Sterbenz

 */

final class RC2Crypt extends SymmetricCipher {

    // PITABLE from the RFC, used in key setup

    private final static int[] PI_TABLE = new int[] {

        0xd9, 0x78, 0xf9, 0xc4, 0x19, 0xdd, 0xb5, 0xed,

        0x28, 0xe9, 0xfd, 0x79, 0x4a, 0xa0, 0xd8, 0x9d,

        0xc6, 0x7e, 0x37, 0x83, 0x2b, 0x76, 0x53, 0x8e,

        0x62, 0x4c, 0x64, 0x88, 0x44, 0x8b, 0xfb, 0xa2,

        0x17, 0x9a, 0x59, 0xf5, 0x87, 0xb3, 0x4f, 0x13,

        0x61, 0x45, 0x6d, 0x8d, 0x09, 0x81, 0x7d, 0x32,

        0xbd, 0x8f, 0x40, 0xeb, 0x86, 0xb7, 0x7b, 0x0b,

        0xf0, 0x95, 0x21, 0x22, 0x5c, 0x6b, 0x4e, 0x82,

        0x54, 0xd6, 0x65, 0x93, 0xce, 0x60, 0xb2, 0x1c,

        0x73, 0x56, 0xc0, 0x14, 0xa7, 0x8c, 0xf1, 0xdc,

        0x12, 0x75, 0xca, 0x1f, 0x3b, 0xbe, 0xe4, 0xd1,

        0x42, 0x3d, 0xd4, 0x30, 0xa3, 0x3c, 0xb6, 0x26,

        0x6f, 0xbf, 0x0e, 0xda, 0x46, 0x69, 0x07, 0x57,

        0x27, 0xf2, 0x1d, 0x9b, 0xbc, 0x94, 0x43, 0x03,

        0xf8, 0x11, 0xc7, 0xf6, 0x90, 0xef, 0x3e, 0xe7,

        0x06, 0xc3, 0xd5, 0x2f, 0xc8, 0x66, 0x1e, 0xd7,

        0x08, 0xe8, 0xea, 0xde, 0x80, 0x52, 0xee, 0xf7,

        0x84, 0xaa, 0x72, 0xac, 0x35, 0x4d, 0x6a, 0x2a,

        0x96, 0x1a, 0xd2, 0x71, 0x5a, 0x15, 0x49, 0x74,

        0x4b, 0x9f, 0xd0, 0x5e, 0x04, 0x18, 0xa4, 0xec,

        0xc2, 0xe0, 0x41, 0x6e, 0x0f, 0x51, 0xcb, 0xcc,

        0x24, 0x91, 0xaf, 0x50, 0xa1, 0xf4, 0x70, 0x39,

        0x99, 0x7c, 0x3a, 0x85, 0x23, 0xb8, 0xb4, 0x7a,

        0xfc, 0x02, 0x36, 0x5b, 0x25, 0x55, 0x97, 0x31,

        0x2d, 0x5d, 0xfa, 0x98, 0xe3, 0x8a, 0x92, 0xae,

        0x05, 0xdf, 0x29, 0x10, 0x67, 0x6c, 0xba, 0xc9,

        0xd3, 0x00, 0xe6, 0xcf, 0xe1, 0x9e, 0xa8, 0x2c,

        0x63, 0x16, 0x01, 0x3f, 0x58, 0xe2, 0x89, 0xa9,

        0x0d, 0x38, 0x34, 0x1b, 0xab, 0x33, 0xff, 0xb0,

        0xbb, 0x48, 0x0c, 0x5f, 0xb9, 0xb1, 0xcd, 0x2e,

        0xc5, 0xf3, 0xdb, 0x47, 0xe5, 0xa5, 0x9c, 0x77,

        0x0a, 0xa6, 0x20, 0x68, 0xfe, 0x7f, 0xc1, 0xad,

    };

    // expanded key, 64 times 16-bit words

    private final int[] expandedKey;

    // effective key bits

    private int effectiveKeyBits;

    RC2Crypt() {

        expandedKey = new int[64];

    }

    int getBlockSize() {

        return 8;

    }

    int getEffectiveKeyBits() {

        return effectiveKeyBits;

    }

    /**

     * Initializes the effective key bit size. This method is a hook to

     * allow RC2Cipher to initialize the effective key size.

     */

    void initEffectiveKeyBits(int effectiveKeyBits) {

        this.effectiveKeyBits = effectiveKeyBits;

    }

    static void checkKey(String algorithm, int keyLength)

            throws InvalidKeyException {

        if (algorithm.equals("RC2") == false) {

            throw new InvalidKeyException("Key algorithm must be RC2");

        }

        if ((keyLength < 5) || (keyLength > 128)) {

            throw new InvalidKeyException

                ("RC2 key length must be between 40 and 1024 bit");

        }

    }

    void init(boolean decrypting, String algorithm, byte[] key)

            throws InvalidKeyException {

        int keyLength = key.length;

        if (effectiveKeyBits == 0) {

            effectiveKeyBits = keyLength << 3;

        }

        checkKey(algorithm, keyLength);

        // key buffer, the L[] byte array from the spec

        byte[] expandedKeyBytes = new byte[128];

        // place key into key buffer

        System.arraycopy(key, 0, expandedKeyBytes, 0, keyLength);

        // first loop

        int t = expandedKeyBytes[keyLength - 1];

        for (int i = keyLength; i < 128; i++) {

            t = PI_TABLE[(t + expandedKeyBytes[i - keyLength]) & 0xff];

            expandedKeyBytes[i] = (byte)t;

        }

        int t8 = (effectiveKeyBits + 7) >> 3;

        int tm = 0xff >> (-effectiveKeyBits & 7);

        // second loop, reduce search space to effective key bits

        t = PI_TABLE[expandedKeyBytes[128 - t8] & tm];

        expandedKeyBytes[128 - t8] = (byte)t;

        for (int i = 127 - t8; i >= 0; i--) {

            t = PI_TABLE[t ^ (expandedKeyBytes[i + t8] & 0xff)];

            expandedKeyBytes[i] = (byte)t;

        }

        // byte to short conversion, little endian (copy into K[])

        for (int i = 0, j = 0; i < 64; i++, j += 2) {

            t =  (expandedKeyBytes[j    ] & 0xff)

              + ((expandedKeyBytes[j + 1] & 0xff) << 8);

            expandedKey[i] = t;

        }

    }

    /**

     * Encrypt a single block. Note that in a few places we omit a "& 0xffff"

     * and allow variables to become larger than 16 bit. This still works

     * because there is never a 32 bit overflow.

     */

    void encryptBlock(byte[] in, int inOfs, byte[] out, int outOfs) {

        int R0 =  (in[inOfs    ] & 0xff)

               + ((in[inOfs + 1] & 0xff) << 8);

        int R1 =  (in[inOfs + 2] & 0xff)

               + ((in[inOfs + 3] & 0xff) << 8);

        int R2 =  (in[inOfs + 4] & 0xff)

               + ((in[inOfs + 5] & 0xff) << 8);

        int R3 =  (in[inOfs + 6] & 0xff)

               + ((in[inOfs + 7] & 0xff) << 8);

        // 5 mixing rounds

        for (int i = 0; i < 20; i += 4) {

            R0 = (R0 + expandedKey[i    ] + (R3 & R2) + (~R3 & R1)) & 0xffff;

            R0 = (R0 << 1) | (R0 >>> 15);

            R1 = (R1 + expandedKey[i + 1] + (R0 & R3) + (~R0 & R2)) & 0xffff;

            R1 = (R1 << 2) | (R1 >>> 14);

            R2 = (R2 + expandedKey[i + 2] + (R1 & R0) + (~R1 & R3)) & 0xffff;

            R2 = (R2 << 3) | (R2 >>> 13);

            R3 = (R3 + expandedKey[i + 3] + (R2 & R1) + (~R2 & R0)) & 0xffff;

            R3 = (R3 << 5) | (R3 >>> 11);

        }

        // 1 mashing round

        R0 += expandedKey[R3 & 0x3f];

        R1 += expandedKey[R0 & 0x3f];

        R2 += expandedKey[R1 & 0x3f];

        R3 += expandedKey[R2 & 0x3f];

        // 6 mixing rounds

        for (int i = 20; i < 44; i += 4) {

            R0 = (R0 + expandedKey[i    ] + (R3 & R2) + (~R3 & R1)) & 0xffff;

            R0 = (R0 << 1) | (R0 >>> 15);

            R1 = (R1 + expandedKey[i + 1] + (R0 & R3) + (~R0 & R2)) & 0xffff;

            R1 = (R1 << 2) | (R1 >>> 14);

            R2 = (R2 + expandedKey[i + 2] + (R1 & R0) + (~R1 & R3)) & 0xffff;

            R2 = (R2 << 3) | (R2 >>> 13);

            R3 = (R3 + expandedKey[i + 3] + (R2 & R1) + (~R2 & R0)) & 0xffff;

            R3 = (R3 << 5) | (R3 >>> 11);

        }

        // 1 mashing round

        R0 += expandedKey[R3 & 0x3f];

        R1 += expandedKey[R0 & 0x3f];

        R2 += expandedKey[R1 & 0x3f];

        R3 += expandedKey[R2 & 0x3f];

        // 5 mixing rounds

        for (int i = 44; i < 64; i += 4) {

            R0 = (R0 + expandedKey[i    ] + (R3 & R2) + (~R3 & R1)) & 0xffff;

            R0 = (R0 << 1) | (R0 >>> 15);

            R1 = (R1 + expandedKey[i + 1] + (R0 & R3) + (~R0 & R2)) & 0xffff;

            R1 = (R1 << 2) | (R1 >>> 14);

            R2 = (R2 + expandedKey[i + 2] + (R1 & R0) + (~R1 & R3)) & 0xffff;

            R2 = (R2 << 3) | (R2 >>> 13);

            R3 = (R3 + expandedKey[i + 3] + (R2 & R1) + (~R2 & R0)) & 0xffff;

            R3 = (R3 << 5) | (R3 >>> 11);

        }

        out[outOfs    ] = (byte)R0;

        out[outOfs + 1] = (byte)(R0 >> 8);

        out[outOfs + 2] = (byte)R1;

        out[outOfs + 3] = (byte)(R1 >> 8);

        out[outOfs + 4] = (byte)R2;

        out[outOfs + 5] = (byte)(R2 >> 8);

        out[outOfs + 6] = (byte)R3;

        out[outOfs + 7] = (byte)(R3 >> 8);

    }

    void decryptBlock(byte[] in, int inOfs, byte[] out, int outOfs) {

        int R0 =  (in[inOfs    ] & 0xff)

               + ((in[inOfs + 1] & 0xff) << 8);

        int R1 =  (in[inOfs + 2] & 0xff)

               + ((in[inOfs + 3] & 0xff) << 8);

        int R2 =  (in[inOfs + 4] & 0xff)

               + ((in[inOfs + 5] & 0xff) << 8);

        int R3 =  (in[inOfs + 6] & 0xff)

               + ((in[inOfs + 7] & 0xff) << 8);

        // 5 r-mixing rounds

        for(int i = 64; i > 44; i -= 4) {

            R3 = ((R3 << 11) | (R3 >>> 5)) & 0xffff;

            R3 = (R3 - expandedKey[i - 1] - (R2 & R1) - (~R2 & R0)) & 0xffff;

            R2 = ((R2 << 13) | (R2 >>> 3)) & 0xffff;

            R2 = (R2 - expandedKey[i - 2] - (R1 & R0) - (~R1 & R3)) & 0xffff;

            R1 = ((R1 << 14) | (R1 >>> 2)) & 0xffff;

            R1 = (R1 - expandedKey[i - 3] - (R0 & R3) - (~R0 & R2)) & 0xffff;

            R0 = ((R0 << 15) | (R0 >>> 1)) & 0xffff;

            R0 = (R0 - expandedKey[i - 4] - (R3 & R2) - (~R3 & R1)) & 0xffff;

        }

        // 1 r-mashing round

        R3 = (R3 - expandedKey[R2 & 0x3f]) & 0xffff;

        R2 = (R2 - expandedKey[R1 & 0x3f]) & 0xffff;

        R1 = (R1 - expandedKey[R0 & 0x3f]) & 0xffff;

        R0 = (R0 - expandedKey[R3 & 0x3f]) & 0xffff;

        // 6 r-mixing rounds

        for(int i = 44; i > 20; i -= 4) {

            R3 = ((R3 << 11) | (R3 >>> 5)) & 0xffff;

            R3 = (R3 - expandedKey[i - 1] - (R2 & R1) - (~R2 & R0)) & 0xffff;

            R2 = ((R2 << 13) | (R2 >>> 3)) & 0xffff;

            R2 = (R2 - expandedKey[i - 2] - (R1 & R0) - (~R1 & R3)) & 0xffff;

            R1 = ((R1 << 14) | (R1 >>> 2)) & 0xffff;

            R1 = (R1 - expandedKey[i - 3] - (R0 & R3) - (~R0 & R2)) & 0xffff;

            R0 = ((R0 << 15) | (R0 >>> 1)) & 0xffff;

            R0 = (R0 - expandedKey[i - 4] - (R3 & R2) - (~R3 & R1)) & 0xffff;

        }

        // 1 r-mashing round

        R3 = (R3 - expandedKey[R2 & 0x3f]) & 0xffff;

        R2 = (R2 - expandedKey[R1 & 0x3f]) & 0xffff;

        R1 = (R1 - expandedKey[R0 & 0x3f]) & 0xffff;

        R0 = (R0 - expandedKey[R3 & 0x3f]) & 0xffff;

        // 5 r-mixing rounds

        for(int i = 20; i > 0; i -= 4) {

            R3 = ((R3 << 11) | (R3 >>> 5)) & 0xffff;

            R3 = (R3 - expandedKey[i - 1] - (R2 & R1) - (~R2 & R0)) & 0xffff;

            R2 = ((R2 << 13) | (R2 >>> 3)) & 0xffff;

            R2 = (R2 - expandedKey[i - 2] - (R1 & R0) - (~R1 & R3)) & 0xffff;

            R1 = ((R1 << 14) | (R1 >>> 2)) & 0xffff;

            R1 = (R1 - expandedKey[i - 3] - (R0 & R3) - (~R0 & R2)) & 0xffff;

            R0 = ((R0 << 15) | (R0 >>> 1)) & 0xffff;

            R0 = (R0 - expandedKey[i - 4] - (R3 & R2) - (~R3 & R1)) & 0xffff;

        }

        out[outOfs    ] = (byte)R0;

        out[outOfs + 1] = (byte)(R0 >> 8);

        out[outOfs + 2] = (byte)R1;

        out[outOfs + 3] = (byte)(R1 >> 8);

        out[outOfs + 4] = (byte)R2;

        out[outOfs + 5] = (byte)(R2 >> 8);

        out[outOfs + 6] = (byte)R3;

        out[outOfs + 7] = (byte)(R3 >> 8);

    }

}