Subversion Repositories SmartDukaan

package in.shop2020.serving.utils.ebs;

/**
 * This class enciphers or deciphers strings using the RC4 encryption algorithm.
 * 
 * @author R. Prince - Java coded based on the original VB source by Mike
 *         Shaffer
 **/
public class RC4 {
        private byte state[] = new byte[256];
        private int x;
        private int y;

        /**
         * Initializes the class with a string key. The length of a normal key
         * should be between 1 and 2048 bits. But this method doens't check the
         * length at all.
         * 
         * @param key
         *            the encryption/decryption key
         */
        public RC4(String key) throws NullPointerException {
                this(key.getBytes());
        }

        /**
         * Initializes the class with a byte array key. The length of a normal key
         * should be between 1 and 2048 bits. But this method doens't check the
         * length at all.
         * 
         * @param key
         *            the encryption/decryption key
         */
        public RC4(byte[] key) throws NullPointerException {

                for (int i = 0; i < 256; i++) {
                        state[i] = (byte) i;
                }

                x = 0;
                y = 0;

                int index1 = 0;
                int index2 = 0;

                byte tmp;

                if (key == null || key.length == 0) {
                        throw new NullPointerException();
                }

                for (int i = 0; i < 256; i++) {

                        index2 = ((key[index1] & 0xff) + (state[i] & 0xff) + index2) & 0xff;

                        tmp = state[i];
                        state[i] = state[index2];
                        state[index2] = tmp;

                        index1 = (index1 + 1) % key.length;
                }

        }

        /**
         * RC4 encryption/decryption.
         * 
         * @param data
         *            the data to be encrypted/decrypted
         * @return the result of the encryption/decryption
         */
        public byte[] rc4(String data) {
                if (data == null) {
                        return null;
                }

                byte[] tmp = data.getBytes();

                this.rc4(tmp);

                return tmp;
        }

        /**
         * RC4 encryption/decryption.
         * 
         * @param buf
         *            the data to be encrypted/decrypted
         * @return the result of the encryption/decryption
         */
        public byte[] rc4(byte[] buf) {
                // int lx = this.x;
                // int ly = this.y;

                int xorIndex;
                byte tmp;

                if (buf == null) {
                        return null;
                }

                byte[] result = new byte[buf.length];

                for (int i = 0; i < buf.length; i++) {

                        x = (x + 1) & 0xff;
                        y = ((state[x] & 0xff) + y) & 0xff;

                        tmp = state[x];
                        state[x] = state[y];
                        state[y] = tmp;

                        xorIndex = ((state[x] & 0xff) + (state[y] & 0xff)) & 0xff;
                        result[i] = (byte) (buf[i] ^ state[xorIndex]);
                }

                // this.x = lx;
                // this.y = ly;

                return result;
        }

}