android中常用的文本加密方式总结

主要介绍几种主流的加密方式，简单的有SHA-1加密、MD5加密，复杂的有AES加密。前两者是HASH算法加密，后者是对称加密算法。

1、SHA-1加密算法

说明：该算法主要用于简单的文本加密，一般是一行文本

public static String Md5(String str) {
if (str != null && !str.equals("")) {
try {
MessageDigest md5 = MessageDigest.getInstance("MD5");
char[] HEX = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
byte[] md5Byte = md5.digest(str.getBytes("UTF8"));
StringBuffer sb = new StringBuffer();
for (int i = 0; i < md5Byte.length; i++) {
sb.append(HEX[(int) (md5Byte[i] & 0xff) / 16]);
sb.append(HEX[(int) (md5Byte[i] & 0xff) % 16]);
}
str = sb.toString();
} catch (NoSuchAlgorithmException e) {
} catch (Exception e) {
}
}
return str;
}

2、MD5加密算法

说明：一般用于简单的文本加密

private static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5','6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

public static String StringToSHA1(String input)
{
String result="";
try {
MessageDigest sha1Digest=MessageDigest.getInstance("SHA-1");
sha1Digest.update(input.getBytes());
byte[] resultBytes= sha1Digest.digest();
int length=resultBytes.length;
StringBuilder buf = new StringBuilder(length * 2);
// 把密文转换成十六进制的字符串形式
for (int i = 0; i < length; i++) {
buf.append(HEX_DIGITS[(resultBytes[i] >> 4) & 0x0f]);
buf.append(HEX_DIGITS[resultBytes[i] & 0x0f]);
}
result= buf.toString().toUpperCase();
} catch (NoSuchAlgorithmException e) {
result="";
}
return result;
}

3、AES加密算法

说明：该算法可以用于大文本的加密

public class Encryption {
public String str_salt ;
public byte[] bytes_salt ;
private static Encryption encryption ;
private Encryption(){
}
public synchronized static Encryption getInstance() {
if (encryption == null) {
encryption = new Encryption();
}
return encryption ;
}

/*
* 生成随机数，可以当做动态的密钥
* 加密和解密的密钥必须一致，不然将不能解密
*/
public String generateSalt(){
try {
SecureRandom localSecureRandom = SecureRandom.getInstance("SHA1PRNG");
bytes_salt = new byte[20];
localSecureRandom.nextBytes(bytes_salt) ;
str_salt = toHex(bytes_salt) ;
return str_salt ;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

/*
* 加密
*/
public String encrypt(String seed, String cleartext) {
if(!("".equals(seed))&&!("".equals(cleartext))){
byte[] rawKey;
try {
rawKey = getRawKey(seed.getBytes());
byte[] result = encrypt(rawKey, cleartext.getBytes());
return toHex(result);
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}

/*
* 解密
*/
public String decrypt(String seed, String encrypted) {
if(!("".equals(seed))&&!("".equals(encrypted))){
byte[] rawKey;
try {
rawKey = getRawKey(seed.getBytes());
byte[] enc = toByte(encrypted);
byte[] result = decrypt(rawKey, enc);
return new String(result);
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}

private static byte[] getRawKey(byte[] seed) throws Exception {
KeyGenerator kgen = KeyGenerator.getInstance("AES");
SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
sr.setSeed(seed);
kgen.init(128, sr);
SecretKey skey = kgen.generateKey();
byte[] raw = skey.getEncoded();
return raw;
}

private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
byte[] encrypted = cipher.doFinal(clear);
return encrypted;
}

private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, skeySpec);
byte[] decrypted = cipher.doFinal(encrypted);
return decrypted;
}

public static String toHex(String txt) {
return toHex(txt.getBytes());
}
public static String fromHex(String hex) {
return new String(toByte(hex));
}

public static byte[] toByte(String hexString) {
int len = hexString.length()/2;
byte[] result = new byte[len];
for (int i = 0; i < len; i++)
result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
return result;
}

public static String toHex(byte[] buf) {
if (buf == null)
return "";
StringBuffer result = new StringBuffer(2*buf.length);
for (int i = 0; i < buf.length; i++) {
appendHex(result, buf[i]);
}
return result.toString();
}
private final static String HEX = "0123456789ABCDEF";
private static void appendHex(StringBuffer sb, byte b) {
sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
}
}