编码与加密

一、阅读基础

1、基础

一、Base64编码与解码

2、原理

4、代码实现

Base64编码

private static char[] base64EncodeChars = new char[] { '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', '+', '/' };

public static String encrypt(byte[] data) {
        StringBuffer sb = new StringBuffer();
        int len = data.length;
        int i = 0;
        int b1, b2, b3;
        while (i < len) {
            b1 = data[i++] & 0xff;
            if (i == len) {
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[(b1 & 0x3) << 4]);
                sb.append("==");
                break;
            }
            b2 = data[i++] & 0xff;
            if (i == len) {
                sb.append(base64EncodeChars[b1 >>> 2]);
                sb.append(base64EncodeChars[((b1 & 0x03) << 4)
                        | ((b2 & 0xf0) >>> 4)]);
                sb.append(base64EncodeChars[(b2 & 0x0f) << 2]);
                sb.append("=");
                break;
            }
            b3 = data[i++] & 0xff;
            sb.append(base64EncodeChars[b1 >>> 2]);
            sb.append(base64EncodeChars[((b1 & 0x03) << 4)
                    | ((b2 & 0xf0) >>> 4)]);
            sb.append(base64EncodeChars[((b2 & 0x0f) << 2)
                    | ((b3 & 0xc0) >>> 6)]);
            sb.append(base64EncodeChars[b3 & 0x3f]);
        }
        return sb.toString();
    }

Base64解码

private static byte[] base64DecodeChars = new byte[] { -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59,
            60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
            10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1,
            -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37,
            38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1,
            -1, -1 };

public static String decrypt(String str) throws Exception{
        StringBuffer sb = new StringBuffer();
        byte[] data =  str.getBytes("US-ASCII");
        int len = data.length;
        int i = 0;
        int b1, b2, b3, b4;
        while (i < len) {

            do {
                b1 = base64DecodeChars[data[i++]];
            } while (i < len && b1 == -1);
            if (b1 == -1)
                break;

            do {
                b2 = base64DecodeChars[data[i++]];
            } while (i < len && b2 == -1);
            if (b2 == -1)
                break;
            sb.append((char) ((b1 << 2) | ((b2 & 0x30) >>> 4)));

            do {
                b3 = data[i++];
                if (b3 == 61)
                    return sb.toString();
                b3 = base64DecodeChars[b3];
            } while (i < len && b3 == -1);
            if (b3 == -1)
                break;
            sb.append((char) (((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2)));

            do {
                b4 = data[i++];
                if (b4 == 61)
                    return sb.toString();
                b4 = base64DecodeChars[b4];
            } while (i < len && b4 == -1);
            if (b4 == -1)
                break;
            sb.append((char) (((b3 & 0x03) << 6) | b4));
        }
        return sb.toString();
    }

二、AES加密

三、RSA加密

四、MD5加密