● BASE64 严格地说,属于编码格式,而非加密算法
● MD5(Message Digest algorithm 5,信息摘要算法)
● SHA(Secure Hash Algorithm,安全散列算法)
● HMAC(Hash Message Authentication Code,散列消息鉴别码)复杂的对称加密(DES、PBE)、非对称加密算法:
● DES(Data Encryption Standard,数据加密算法)
● PBE(Password-based encryption,基于密码验证)
● RSA(算法的名字以发明者的名字命名:Ron Rivest, AdiShamir 和Leonard Adleman)
● DH(Diffie-Hellman算法,密钥一致协议)
● DSA(Digital Signature Algorithm,数字签名)
● ECC(Elliptic Curves Cryptography,椭圆曲线密码编码学)[/size]
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本篇内容简要介绍BASE64、MD5、SHA、HMAC几种加密算法。
BASE64编码算法不算是真正的加密算法。
MD5、SHA、HMAC这三种加密算法,可谓是非可逆加密,就是不可解密的加密方法,我们称之为单向加密算法。我们通常只把他们作为加密的基础。单纯的以上三种的加密并不可靠。
BASE64
按照RFC2045的定义,Base64被定义为:Base64内容传送编码被设计用来把任意序列的8位字节描述为一种不易被人直接识别的形式。(The Base64 Content-Transfer-Encoding is designed to represent arbitrary sequences of octets in a form that need not be humanly readable.)
常见于邮件、http加密,截取http信息,你就会发现登录操作的用户名、密码字段通过BASE64加密的。
主要就是BASE64Encoder、BASE64Decoder两个类,我们只需要知道使用对应的方法即可。另,BASE加密后产生的字节位数是8的倍数,如果不够位数以=符号填充。
sun不推荐使用它们自己的base64,所以用apache的挺好!
MD5
MD5 -- message-digest algorithm 5 (信息-摘要算法)缩写,广泛用于加密和解密技术,常用于文件校验。校验?不管文件多大,经过MD5后都能生成唯一的MD5值。好比现在的ISO校验,都是MD5校验。怎么用?当然是把ISO经过MD5后产生MD5的值。一般下载linux-ISO的朋友都见过下载链接旁边放着MD5的串。就是用来验证文件是否一致的。
通常我们不直接使用上述MD5加密。通常将MD5产生的字节数组交给BASE64再加密一把,得到相应的字符串。
SHA
SHA(Secure Hash Algorithm,安全散列算法),数字签名等密码学应用中重要的工具,被广泛地应用于电子商务等信息安全领域。虽然,SHA与MD5通过碰撞法都被破解了,但是SHA仍然是公认的安全加密算法,较之MD5更为安全。
HMAC
HMAC(Hash Message Authentication Code,散列消息鉴别码,基于密钥的Hash算法的认证协议。消息鉴别码实现鉴别的原理是,用公开函数和密钥产生一个固定长度的值作为认证标识,用这个标识鉴别消息的完整性。使用一个密钥生成一个固定大小的小数据块,即MAC,并将其加入到消息中,然后传输。接收方利用与发送方共享的密钥进行鉴别认证等。
BASE64的加密解密是双向的,可以求反解。
MD5、SHA以及HMAC是单向加密,任何数据加密后只会产生唯一的一个加密串,通常用来校验数据在传输过程中是否被修改。其中HMAC算法有一个密钥,增强了数据传输过程中的安全性,强化了算法外的不可控因素。[img]http://www.iteye.com/images/smiles/icon_biggrin.gif" alt="[/img]
单向加密的用途主要是为了校验数据在传输过程中是否被修改。
代码如下:
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可变在这里含义很简单,就是最终的加密结果是可变的,而非必需按标准MD5加密实现。Java类库security中的MessageDigest类就提供了MD5加密的支持,实现起来非常方便。为了实现更多效果,我们可以如下设计MD5工具类。
- import java.security.MessageDigest;
-
- public class MD5 {
-
- public static String getMD5ofStr(String origString) {
- String origMD5 = null;
- try {
- MessageDigest md5 = MessageDigest.getInstance("MD5");
-
- byte[] result = md5.digest(origString.getBytes());
- origMD5 = byteArray2HexStr(result);
-
-
-
-
- } catch (Exception e) {
- e.printStackTrace();
- }
- return origMD5;
- }
-
-
- private static String byteArray2HexStr(byte[] bs) {
- StringBuffer sb = new StringBuffer();
- for (byte b : bs) {
- sb.append(byte2HexStr(b));
- }
- return sb.toString();
- }
-
-
- private static String byte2HexStr(byte b) {
- String hexStr = null;
- int n = b;
- if (n < 0) {
-
- n = b & 0x7F + 128;
- }
- hexStr = Integer.toHexString(n / 16) + Integer.toHexString(n % 16);
- return hexStr.toUpperCase();
- }
-
-
- public static String getMD5ofStr(String origString, int times) {
- String md5 = getMD5ofStr(origString);
- for (int i = 0; i < times - 1; i++) {
- md5 = getMD5ofStr(md5);
- }
- return getMD5ofStr(md5);
- }
-
-
- public static boolean verifyPassword(String inputStr, String MD5Code) {
- return getMD5ofStr(inputStr).equals(MD5Code);
- }
-
-
- public static boolean verifyPassword(String inputStr, String MD5Code,
- int times) {
- return getMD5ofStr(inputStr, times).equals(MD5Code);
- }
-
-
- public static void main(String[] args) {
- System.out.println("123:" + getMD5ofStr("123"));
- System.out.println("123456789:" + getMD5ofStr("123456789"));
- System.out.println("sarin:" + getMD5ofStr("sarin"));
- System.out.println("123:" + getMD5ofStr("123", 4));
- }
- }
可以看出实现的过程非常简单,因为由java类库提供了处理支持。但是要清楚的是这种方式产生的密码不是标准的MD5码,它需要进行移位处理才能得到标准MD5码。这个程序的关键之处也在这了,怎么可变?调整移位算法不就可变了么!不进行移位,也能够得到32位的密码,这就不是标准加密了,只要加密和验证过程使用相同的算法就可以了。
MD5加密还是很安全的,像CMD5那些穷举破解的只是针对标准MD5加密的结果进行的,如果自定义移位算法后,它还有效么?可以说是无解的了,所以MD5非常安全可靠。
为了更可变,还提供了多次加密的方法,可以在MD5基础之上继续MD5,就是对32位的第一次加密结果再MD5,恩,这样去破解?没有任何意义。
这样在MIS系统中使用,安全可靠,欢迎交流,希望对使用者有用。
我们最后看看由MD5加密算法实现的类,那是非常庞大的。
- import java.lang.reflect.*;
-
-
- public class MD5 {
-
- static final int S11 = 7;
- static final int S12 = 12;
- static final int S13 = 17;
- static final int S14 = 22;
-
- static final int S21 = 5;
- static final int S22 = 9;
- static final int S23 = 14;
- static final int S24 = 20;
-
- static final int S31 = 4;
- static final int S32 = 11;
- static final int S33 = 16;
- static final int S34 = 23;
-
- static final int S41 = 6;
- static final int S42 = 10;
- static final int S43 = 15;
- static final int S44 = 21;
-
- static final byte[] PADDING = { -128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
- 0 };
-
- private long[] state = new long[4];
- private long[] count = new long[2];
- private byte[] buffer = new byte[64];
-
-
- public String digestHexStr;
-
-
- private byte[] digest = new byte[16];
-
-
- public String getMD5ofStr(String inbuf) {
- md5Init();
- md5Update(inbuf.getBytes(), inbuf.length());
- md5Final();
- digestHexStr = "";
- for (int i = 0; i < 16; i++) {
- digestHexStr += byteHEX(digest[i]);
- }
- return digestHexStr;
-
- }
-
-
- public MD5() {
- md5Init();
-
- return;
- }
-
-
- private void md5Init() {
- count[0] = 0L;
- count[1] = 0L;
-
-
- state[0] = 0x67452301L;
- state[1] = 0xefcdab89L;
- state[2] = 0x98badcfeL;
- state[3] = 0x10325476L;
-
- return;
- }
-
- /* F, G, H ,I 是4个基本的MD5函数,在原始的MD5的C实现中,由于它们是
- 简单的位运算,可能出于效率的考虑把它们实现成了宏,在java中,我们把它们
- 实现成了private方法,名字保持了原来C中的。 */
-
- private long F(long x, long y, long z) {
- return (x & y) | ((~x) & z);
-
- }
-
- private long G(long x, long y, long z) {
- return (x & z) | (y & (~z));
-
- }
-
- private long H(long x, long y, long z) {
- return x ^ y ^ z;
- }
-
- private long I(long x, long y, long z) {
- return y ^ (x | (~z));
- }
-
-
-
- private long FF(long a, long b, long c, long d, long x, long s, long ac) {
- a += F(b, c, d) + x + ac;
- a = ((int) a << s) | ((int) a >>> (32 - s));
- a += b;
- return a;
- }
-
- private long GG(long a, long b, long c, long d, long x, long s, long ac) {
- a += G(b, c, d) + x + ac;
- a = ((int) a << s) | ((int) a >>> (32 - s));
- a += b;
- return a;
- }
-
- private long HH(long a, long b, long c, long d, long x, long s, long ac) {
- a += H(b, c, d) + x + ac;
- a = ((int) a << s) | ((int) a >>> (32 - s));
- a += b;
- return a;
- }
-
- private long II(long a, long b, long c, long d, long x, long s, long ac) {
- a += I(b, c, d) + x + ac;
- a = ((int) a << s) | ((int) a >>> (32 - s));
- a += b;
- return a;
- }
-
-
- private void md5Update(byte[] inbuf, int inputLen) {
-
- int i, index, partLen;
- byte[] block = new byte[64];
- index = (int) (count[0] >>> 3) & 0x3F;
-
- if ((count[0] += (inputLen << 3)) < (inputLen << 3))
- count[1]++;
- count[1] += (inputLen >>> 29);
-
- partLen = 64 - index;
-
-
- if (inputLen >= partLen) {
- md5Memcpy(buffer, inbuf, index, 0, partLen);
- md5Transform(buffer);
-
- for (i = partLen; i + 63 < inputLen; i += 64) {
-
- md5Memcpy(block, inbuf, 0, i, 64);
- md5Transform(block);
- }
- index = 0;
-
- } else
-
- i = 0;
-
-
- md5Memcpy(buffer, inbuf, index, i, inputLen - i);
-
- }
-
-
- private void md5Final() {
- byte[] bits = new byte[8];
- int index, padLen;
-
-
- Encode(bits, count, 8);
-
-
- index = (int) (count[0] >>> 3) & 0x3f;
- padLen = (index < 56) ? (56 - index) : (120 - index);
- md5Update(PADDING, padLen);
-
-
- md5Update(bits, 8);
-
-
- Encode(digest, state, 16);
-
- }
-
-
-
- private void md5Memcpy(byte[] output, byte[] input, int outpos, int inpos, int len) {
- int i;
-
- for (i = 0; i < len; i++)
- output[outpos + i] = input[inpos + i];
- }
-
-
- private void md5Transform(byte block[]) {
- long a = state[0], b = state[1], c = state[2], d = state[3];
- long[] x = new long[16];
-
- Decode(x, block, 64);
-
-
- a = FF(a, b, c, d, x[0], S11, 0xd76aa478L);
- d = FF(d, a, b, c, x[1], S12, 0xe8c7b756L);
- c = FF(c, d, a, b, x[2], S13, 0x242070dbL);
- b = FF(b, c, d, a, x[3], S14, 0xc1bdceeeL);
- a = FF(a, b, c, d, x[4], S11, 0xf57c0fafL);
- d = FF(d, a, b, c, x[5], S12, 0x4787c62aL);
- c = FF(c, d, a, b, x[6], S13, 0xa8304613L);
- b = FF(b, c, d, a, x[7], S14, 0xfd469501L);
- a = FF(a, b, c, d, x[8], S11, 0x698098d8L);
- d = FF(d, a, b, c, x[9], S12, 0x8b44f7afL);
- c = FF(c, d, a, b, x[10], S13, 0xffff5bb1L);
- b = FF(b, c, d, a, x[11], S14, 0x895cd7beL);
- a = FF(a, b, c, d, x[12], S11, 0x6b901122L);
- d = FF(d, a, b, c, x[13], S12, 0xfd987193L);
- c = FF(c, d, a, b, x[14], S13, 0xa679438eL);
- b = FF(b, c, d, a, x[15], S14, 0x49b40821L);
-
-
- a = GG(a, b, c, d, x[1], S21, 0xf61e2562L);
- d = GG(d, a, b, c, x[6], S22, 0xc040b340L);
- c = GG(c, d, a, b, x[11], S23, 0x265e5a51L);
- b = GG(b, c, d, a, x[0], S24, 0xe9b6c7aaL);
- a = GG(a, b, c, d, x[5], S21, 0xd62f105dL);
- d = GG(d, a, b, c, x[10], S22, 0x2441453L);
- c = GG(c, d, a, b, x[15], S23, 0xd8a1e681L);
- b = GG(b, c, d, a, x[4], S24, 0xe7d3fbc8L);
- a = GG(a, b, c, d, x[9], S21, 0x21e1cde6L);
- d = GG(d, a, b, c, x[14], S22, 0xc33707d6L);
- c = GG(c, d, a, b, x[3], S23, 0xf4d50d87L);
- b = GG(b, c, d, a, x[8], S24, 0x455a14edL);
- a = GG(a, b, c, d, x[13], S21, 0xa9e3e905L);
- d = GG(d, a, b, c, x[2], S22, 0xfcefa3f8L);
- c = GG(c, d, a, b, x[7], S23, 0x676f02d9L);
- b = GG(b, c, d, a, x[12], S24, 0x8d2a4c8aL);
-
-
- a = HH(a, b, c, d, x[5], S31, 0xfffa3942L);
- d = HH(d, a, b, c, x[8], S32, 0x8771f681L);
- c = HH(c, d, a, b, x[11], S33, 0x6d9d6122L);
- b = HH(b, c, d, a, x[14], S34, 0xfde5380cL);
- a = HH(a, b, c, d, x[1], S31, 0xa4beea44L);
- d = HH(d, a, b, c, x[4], S32, 0x4bdecfa9L);
- c = HH(c, d, a, b, x[7], S33, 0xf6bb4b60L);
- b = HH(b, c, d, a, x[10], S34, 0xbebfbc70L);
- a = HH(a, b, c, d, x[13], S31, 0x289b7ec6L);
- d = HH(d, a, b, c, x[0], S32, 0xeaa127faL);
- c = HH(c, d, a, b, x[3], S33, 0xd4ef3085L);
- b = HH(b, c, d, a, x[6], S34, 0x4881d05L);
- a = HH(a, b, c, d, x[9], S31, 0xd9d4d039L);
- d = HH(d, a, b, c, x[12], S32, 0xe6db99e5L);
- c = HH(c, d, a, b, x[15], S33, 0x1fa27cf8L);
- b = HH(b, c, d, a, x[2], S34, 0xc4ac5665L);
-
-
- a = II(a, b, c, d, x[0], S41, 0xf4292244L);
- d = II(d, a, b, c, x[7], S42, 0x432aff97L);
- c = II(c, d, a, b, x[14], S43, 0xab9423a7L);
- b = II(b, c, d, a, x[5], S44, 0xfc93a039L);
- a = II(a, b, c, d, x[12], S41, 0x655b59c3L);
- d = II(d, a, b, c, x[3], S42, 0x8f0ccc92L);
- c = II(c, d, a, b, x[10], S43, 0xffeff47dL);
- b = II(b, c, d, a, x[1], S44, 0x85845dd1L);
- a = II(a, b, c, d, x[8], S41, 0x6fa87e4fL);
- d = II(d, a, b, c, x[15], S42, 0xfe2ce6e0L);
- c = II(c, d, a, b, x[6], S43, 0xa3014314L);
- b = II(b, c, d, a, x[13], S44, 0x4e0811a1L);
- a = II(a, b, c, d, x[4], S41, 0xf7537e82L);
- d = II(d, a, b, c, x[11], S42, 0xbd3af235L);
- c = II(c, d, a, b, x[2], S43, 0x2ad7d2bbL);
- b = II(b, c, d, a, x[9], S44, 0xeb86d391L);
-
- state[0] += a;
- state[1] += b;
- state[2] += c;
- state[3] += d;
-
- }
-
-
- private void Encode(byte[] output, long[] input, int len) {
- int i, j;
-
- for (i = 0, j = 0; j < len; i++, j += 4) {
- output[j] = (byte) (input[i] & 0xffL);
- output[j + 1] = (byte) ((input[i] >>> 8) & 0xffL);
- output[j + 2] = (byte) ((input[i] >>> 16) & 0xffL);
- output[j + 3] = (byte) ((input[i] >>> 24) & 0xffL);
- }
- }
-
-
- private void Decode(long[] output, byte[] input, int len) {
- int i, j;
-
- for (i = 0, j = 0; j < len; i++, j += 4)
- output[i] = b2iu(input[j]) | (b2iu(input[j + 1]) << 8) | (b2iu(input[j + 2]) << 16)
- | (b2iu(input[j + 3]) << 24);
-
- return;
- }
-
-
- public static long b2iu(byte b) {
- return b < 0 ? b & 0x7F + 128 : b;
- }
-
-
- public static String byteHEX(byte ib) {
- char[] Digit = { ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘, ‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘, ‘F‘ };
- char[] ob = new char[2];
- ob[0] = Digit[(ib >>> 4) & 0X0F];
- ob[1] = Digit[ib & 0X0F];
- String s = new String(ob);
- return s;
- }
-
- public static void main(String args[]) {
-
- MD5 m = new MD5();
- if (Array.getLength(args) == 0) {
-
- System.out.println("MD5 Test suite:");
- System.out.println("MD5(\"\"):" + m.getMD5ofStr(""));
- System.out.println("MD5(\"a\"):" + m.getMD5ofStr("a"));
- System.out.println("MD5(\"abc\"):" + m.getMD5ofStr("abc"));
- System.out.println("MD5(\"11\"):" + m.getMD5ofStr("11"));
- System.out.println("MD5(\"123\"):" + m.getMD5ofStr("123"));
- System.out.println("MD5(\"message digest\"):" + m.getMD5ofStr("message digest"));
- System.out.println("MD5(\"abcdefghijklmnopqrstuvwxyz\"):" + m.getMD5ofStr("abcdefghijklmnopqrstuvwxyz"));
- System.out.println("MD5(\"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789\"):"
- + m.getMD5ofStr("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"));
- } else
- System.out.println("MD5(" + args[0] + ")=" + m.getMD5ofStr(args[0]));
-
- }
-
- }