java加密算法base64

加密和解密

（一）java自带的加密和解密

import sun.misc.BASE64Decoder;

public class Base64Utils {

public static String getBASE64(byte[] b) {
String s = null;
if (b != null) {
s = new sun.misc.BASE64Encoder().encode(b);
}
return s;
}

public static byte[] getFromBASE64(String s) {
byte[] b = null;
if (s != null) {
BASE64Decoder decoder = new BASE64Decoder();
try {
b = decoder.decodeBuffer(s);
return b;
} catch (Exception e) {
e.printStackTrace();
}
}
return b;
}
}

（二）自己写加密算法

import java.io.UnsupportedEncodingException;

public class Base64 {

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', '+', '/'};

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 encode(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();
}

public static byte[] decode(String str) throws UnsupportedEncodingException {
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().getBytes("iso8859-1");
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().getBytes("iso8859-1");
b4 = base64DecodeChars[b4];
} while (i < len && b4 == -1);
if (b4 == -1) break;
sb.append((char) (((b3 & 0x03) << 6) | b4));
}
return sb.toString().getBytes("iso8859-1");
}
public static void main(String[] args) throws UnsupportedEncodingException {
String s = "abcd";
System.out.println("加密前：" + s);
String x = encode(s.getBytes());
System.out.println("加密后：" + x);
String x1 = new String(decode(x));
System.out.println("解密后：" + x1);
}
}

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