Android AES,RSA方式数据加密解密代码记录

class Base64Encoder extends FilterOutputStream {

    private static final char[] chars = {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
            'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
            'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
            'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
            'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
            'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
            '8', '9', '+', '/'
    };

    private int charCount;
    private int carryOver;

    /***
     * Constructs a new Base64 encoder that writes output to the given
     * OutputStream.
     *
     * @param out the output stream
     */
    public Base64Encoder(OutputStream out) {
        super(out);
    }

    /***
     * Writes the given byte to the output stream in an encoded form.
     *
     * @throws IOException if an I/O error occurs
     */
    public void write(int b) throws IOException {
        // Take 24-bits from three octets, translate into four encoded chars
        // Break lines at 76 chars
        // If necessary, pad with 0 bits on the right at the end
        // Use = signs as padding at the end to ensure encodedLength % 4 == 0

        // Remove the sign bit,
        // thanks to Christian Schweingruber <[email protected]>
        if (b < 0) {
            b += 256;
        }

        // First byte use first six bits, save last two bits
        if (charCount % 3 == 0) {
            int lookup = b >> 2;
            carryOver = b & 3;        // last two bits
            out.write(chars[lookup]);
        }
        // Second byte use previous two bits and first four new bits,
        // save last four bits
        else if (charCount % 3 == 1) {
            int lookup = ((carryOver << 4) + (b >> 4)) & 63;
            carryOver = b & 15;       // last four bits
            out.write(chars[lookup]);
        }
        // Third byte use previous four bits and first two new bits,
        // then use last six new bits
        else if (charCount % 3 == 2) {
            int lookup = ((carryOver << 2) + (b >> 6)) & 63;
            out.write(chars[lookup]);
            lookup = b & 63;          // last six bits
            out.write(chars[lookup]);
            carryOver = 0;
        }
        charCount++;

        // Add newline every 76 output chars (that's 57 input chars)
        if (charCount % 57 == 0) {
            out.write('\n');
        }
    }

    /***
     * Writes the given byte array to the output stream in an
     * encoded form.
     *
     * @param buf the data to be written
     * @param off the start offset of the data
     * @param len the length of the data
     * @throws IOException if an I/O error occurs
     */
    public void write(byte[] buf, int off, int len) throws IOException {
        // This could of course be optimized
        for (int i = 0; i < len; i++) {
            write(buf[off + i]);
        }
    }

    /***
     * Closes the stream, this MUST be called to ensure proper padding is
     * written to the end of the output stream.
     *
     * @throws IOException if an I/O error occurs
     */
    public void close() throws IOException {
        // Handle leftover bytes
        if (charCount % 3 == 1) {  // one leftover
            int lookup = (carryOver << 4) & 63;
            out.write(chars[lookup]);
            out.write('=');
            out.write('=');
        } else if (charCount % 3 == 2) {  // two leftovers
            int lookup = (carryOver << 2) & 63;
            out.write(chars[lookup]);
            out.write('=');
        }
        super.close();
    }

    /***
     * Returns the encoded form of the given unencoded string.  The encoder
     * uses the ISO-8859-1 (Latin-1) encoding to convert the string to bytes.
     * For greater control over the encoding, encode the string to bytes
     * yourself and use encode(byte[]).
     *
     * @param unencoded the string to encode
     * @return the encoded form of the unencoded string
     */
    public static String encode(String unencoded) {
        byte[] bytes = null;
        try {
            bytes = unencoded.getBytes("UTF-8");
        } catch (UnsupportedEncodingException ignored) {
        }
        return encode(bytes);
    }

    /***
     * Returns the encoded form of the given unencoded string.
     *
     * @param bytes the bytes to encode
     * @return the encoded form of the unencoded string
     */
    public static String encode(byte[] bytes) {
        ByteArrayOutputStream out =
                new ByteArrayOutputStream((int) (bytes.length * 1.37));
        Base64Encoder encodedOut = new Base64Encoder(out);

        try {
            encodedOut.write(bytes);
            encodedOut.close();

            return out.toString("UTF-8");
        } catch (IOException ignored) {
            return null;
        }
    }
}
class Base64Encoder extends FilterOutputS