文章来源：http://www.cnblogs.com/whoislcj/p/5473030.html
前言：
项目中除了登陆，支付等接口采用rsa非对称加密，之外的采用aes对称加密，今天我们来认识一下aes加密。
其他几种加密方式：
Android数据加密之Rsa加密
Android数据加密之Aes加密
Android数据加密之Des加密
Android数据加密之MD5加密
Android数据加密之Base64编码算法
Android数据加密之异或加密算法
什么是aes加密？
高级加密标准（英语：Advanced Encryption Standard，缩写：AES），在密码学中又称Rijndael加密法，是美国联邦政府采用的一种区块加密标准。这个标准用来替代原先的DES，已经被多方分析且广为全世界所使用。
接下来我们来实际看下具体怎么实现：
对于AesUtils类常量简介：
private final static String HEX = "0123456789ABCDEF";
private static final String CBC_PKCS5_PADDING = "AES/CBC/PKCS5Padding";//AES是加密方式 CBC是工作模式 PKCS5Padding是填充模式
private static final String AES = "AES";//AES 加密
private static final String SHA1PRNG="SHA1PRNG";//// SHA1PRNG 强随机种子算法, 要区别4.2以上版本的调用方法
如何生成一个随机Key？
/*
* 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 static String generateKey() {
try {
SecureRandom localSecureRandom = SecureRandom.getInstance(SHA1PRNG);
byte[] bytes_key = new byte[20];
localSecureRandom.nextBytes(bytes_key);
String str_key = toHex(bytes_key);
return str_key;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
Aes密钥处理
// 对密钥进行处理
private static byte[] getRawKey(byte[] seed) throws Exception {
KeyGenerator kgen = KeyGenerator.getInstance(AES);
//for android
SecureRandom sr = null;
// 在4.2以上版本中，SecureRandom获取方式发生了改变
if (android.os.Build.VERSION.SDK_INT >= 17) {
sr = SecureRandom.getInstance(SHA1PRNG, "Crypto");
} else {
sr = SecureRandom.getInstance(SHA1PRNG);
}
// for Java
// secureRandom = SecureRandom.getInstance(SHA1PRNG);
sr.setSeed(seed);
kgen.init(128, sr); //256 bits or 128 bits,192bits
//AES中128位密钥版本有10个加密循环，192比特密钥版本有12个加密循环，256比特密钥版本则有14个加密循环。
SecretKey skey = kgen.generateKey();
byte[] raw = skey.getEncoded();
return raw;
}
Aes加密过程
/*
* 加密
*/
public static String encrypt(String key, String cleartext) {
if (TextUtils.isEmpty(cleartext)) {
return cleartext;
}
try {
byte[] result = encrypt(key, cleartext.getBytes());
return Base64Encoder.encode(result);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/*
* 加密
*/
private static byte[] encrypt(String key, byte[] clear) throws Exception {
byte[] raw = getRawKey(key.getBytes());
SecretKeySpec skeySpec = new SecretKeySpec(raw, AES);
Cipher cipher = Cipher.getInstance(CBC_PKCS5_PADDING);
cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(new byte[cipher.getBlockSize()]));
byte[] encrypted = cipher.doFinal(clear);
return encrypted;
}
Aes解密过程
/*
* 解密
*/
public static String decrypt(String key, String encrypted) {
if (TextUtils.isEmpty(encrypted)) {
return encrypted;
}
try {
byte[] enc = Base64Decoder.decodeToBytes(encrypted);
byte[] result = decrypt(key, enc);
return new String(result);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/*
* 解密
*/
private static byte[] decrypt(String key, byte[] encrypted) throws Exception {
byte[] raw = getRawKey(key.getBytes());
SecretKeySpec skeySpec = new SecretKeySpec(raw, AES);
Cipher cipher = Cipher.getInstance(CBC_PKCS5_PADDING);
cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(new byte[cipher.getBlockSize()]));
byte[] decrypted = cipher.doFinal(encrypted);
return decrypted;
}
二进制转字符
//二进制转字符
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 static void appendHex(StringBuffer sb, byte b) {
sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
}
测试程序：
List personList = new ArrayList<>();
int testMaxCount = 1000;//测试的最大数据条数
//添加测试数据
for (int i = 0; i < testMaxCount; i++) {
Person person = new Person();
person.setAge(i);
person.setName(String.valueOf(i));
personList.add(person);
}
//FastJson生成json数据
String jsonData = JsonUtils.objectToJsonForFastJson(personList);
Log.e("MainActivity", "AES加密前json数据 ---->" + jsonData);
Log.e("MainActivity", "AES加密前json数据长度 ---->" + jsonData.length());
//生成一个动态key
String secretKey = AesUtils.generateKey();
Log.e("MainActivity", "AES动态secretKey ---->" + secretKey);
//AES加密
long start = System.currentTimeMillis();
String encryStr = AesUtils.encrypt(secretKey, jsonData);
long end = System.currentTimeMillis();
Log.e("MainActivity", "AES加密耗时 cost time---->" + (end - start));
Log.e("MainActivity", "AES加密后json数据 ---->" + encryStr);
Log.e("MainActivity", "AES加密后json数据长度 ---->" + encryStr.length());
//AES解密
start = System.currentTimeMillis();
String decryStr = AesUtils.decrypt(secretKey, encryStr);
end = System.currentTimeMillis();
Log.e("MainActivity", "AES解密耗时 cost time---->" + (end - start));
Log.e("MainActivity", "AES解密后json数据 ---->" + decryStr);
运行耗时：
数据前后变化：
由此可见对称Aes效率还是比较高的
补充关于Base64Decoder类和Base64Encoder类
package com.whoislcj.testhttp.utils;
import android.text.TextUtils;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
public class Base64Decoder extends FilterInputStream {
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', '+', '/' };
// A mapping between char values and six-bit integers
private static final int[] ints = new int[128];
static {
for (int i = 0; i < 64; i++) {
ints[chars[i]] = i;
}
}
private int charCount;
private int carryOver;
/***
* Constructs a new Base64 decoder that reads input from the given
* InputStream.
*
* @param in
* the input stream
*/
private Base64Decoder(InputStream in) {
super(in);
}
/***
* Returns the next decoded character from the stream, or -1 if end of
* stream was reached.
*
* @return the decoded character, or -1 if the end of the input stream is
* reached
* @exception IOException
* if an I/O error occurs
*/
public int read() throws IOException {
// Read the next non-whitespace character
int x;
do {
x = in.read();
if (x == -1) {
return -1;
}
} while (Character.isWhitespace((char) x));
charCount++;
// The '=' sign is just padding
if (x == '=') {
return -1; // effective end of stream
}
// Convert from raw form to 6-bit form
x = ints[x];
// Calculate which character we're decoding now
int mode = (charCount - 1) % 4;
// First char save all six bits, go for another
if (mode == 0) {
carryOver = x & 63;
return read();
}
// Second char use previous six bits and first two new bits,
// save last four bits
else if (mode == 1) {
int decoded = ((carryOver << 2) + (x >> 4)) & 255;
carryOver = x & 15;
return decoded;
}
// Third char use previous four bits and first four new bits,
// save last two bits
else if (mode == 2) {
int decoded = ((carryOver << 4) + (x >> 2)) & 255;
carryOver = x & 3;
return decoded;
}
// Fourth char use previous two bits and all six new bits
else if (mode == 3) {
int decoded = ((carryOver << 6) + x) & 255;
return decoded;
}
return -1; // can't actually reach this line
}
/***
* Reads decoded data into an array of bytes and returns the actual number
* of bytes read, or -1 if end of stream was reached.
*
* @param buf
* the buffer into which the data is read
* @param off
* the start offset of the data
* @param len
* the maximum number of bytes to read
* @return the actual number of bytes read, or -1 if the end of the input
* stream is reached
* @exception IOException
* if an I/O error occurs
*/
public int read(byte[] buf, int off, int len) throws IOException {
if (buf.length < (len + off - 1)) {
throw new IOException("The input buffer is too small: " + len + " bytes requested starting at offset " + off + " while the buffer " + " is only " + buf.length + " bytes long.");
}
// This could of course be optimized
int i;
for (i = 0; i < len; i++) {
int x = read();
if (x == -1 && i == 0) { // an immediate -1 returns -1
return -1;
} else if (x == -1) { // a later -1 returns the chars read so far
break;
}
buf[off + i] = (byte) x;
}
return i;
}
/***
* Returns the decoded form of the given encoded string, as a String. Note
* that not all binary data can be represented as a String, so this method
* should only be used for encoded String data. Use decodeToBytes()
* otherwise.
*
* @param encoded
* the string to decode
* @return the decoded form of the encoded string
*/
public static String decode(String encoded) {
if (TextUtils.isEmpty(encoded)) {
return "";
}
return new String(decodeToBytes(encoded));
}
/***
* Returns the decoded form of the given encoded string, as bytes.
*
* @param encoded
* the string to decode
* @return the decoded form of the encoded string
*/
public static byte[] decodeToBytes(String encoded) {
byte[] bytes = encoded.getBytes();
Base64Decoder in = new Base64Decoder(new ByteArrayInputStream(bytes));
ByteArrayOutputStream out = new ByteArrayOutputStream((int) (bytes.length * 0.75));
try {
byte[] buf = new byte[4 * 1024]; // 4K buffer
int bytesRead;
while ((bytesRead = in.read(buf)) != -1) {
out.write(buf, 0, bytesRead);
}
return out.toByteArray();
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
try {
in.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
try {
out.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
}
Base64Decoder
package com.whoislcj.testhttp.utils;
import java.io.ByteArrayOutputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
public 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;
// 是否每76字节换行
private boolean isWrapBreak = true;
/***
* Constructs a new Base64 encoder that writes output to the given
* OutputStream.
*
* @param out
* the output stream
*/
private Base64Encoder(OutputStream out) {
super(out);
}
/***
* Constructs a new Base64 encoder that writes output to the given
* OutputStream.
*
* @param out
* the output stream
*/
private Base64Encoder(OutputStream out, boolean isWrapBreak) {
this(out);
this.isWrapBreak = isWrapBreak;
}
/***
* Writes the given byte to the output stream in an encoded form.
*
* @exception 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
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 (this.isWrapBreak && 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
* @exception 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.
*
* @exception 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.
* 默认是否每76字节换行
*
* @param bytes
* the bytes to encode
* @return the encoded form of the unencoded string
* @throws IOException
*/
public static String encode(byte[] bytes) {
return encode(bytes, true);
}
/***
* Returns the encoded form of the given unencoded string.
*
* @param bytes
* the bytes to encode
* @param isWrapBreak
* 是否每76字节换行
* @return the encoded form of the unencoded string
* @throws IOException
*/
public static String encode(byte[] bytes, boolean isWrapBreak) {
ByteArrayOutputStream out = new ByteArrayOutputStream((int) (bytes.length * 1.4));
Base64Encoder encodedOut = new Base64Encoder(out, isWrapBreak);
try {
encodedOut.write(bytes);
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
try {
encodedOut.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
return out.toString();
}
// public static void main(String[] args) throws Exception {
// if (args.length != 1) {
// System.err
// .println("Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");
// return;
// }
// Base64Encoder encoder = null;
// BufferedInputStream in = null;
// try {
// encoder = new Base64Encoder(System.out);
// in = new BufferedInputStream(new FileInputStream(args[0]));
//
// byte[] buf = new byte[4 * 1024]; // 4K buffer
// int bytesRead;
// while ((bytesRead = in.read(buf)) != -1) {
// encoder.write(buf, 0, bytesRead);
// }
// } finally {
// if (in != null)
// in.close();
// if (encoder != null)
// encoder.close();
// }
// }
}
Base64Encoder