android使用AES加密和解密文件实例代码

package com.vsoontech.p2p.sample;  import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.security.InvalidKeyException; import java.security.Key; import java.security.NoSuchAlgorithmException; import java.security.SecureRandom;  import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeException; import javax.crypto.KeyGenerator; import javax.crypto.NoSuchPaddingException; import javax.crypto.ShortBufferException;    public enum AES {   INSTANCE;   private Key key;       public String generateKey() throws NoSuchAlgorithmException {     KeyGenerator keygen = KeyGenerator.getInstance("AES");     SecureRandom random = new SecureRandom();     keygen.init(random);     this.key = keygen.generateKey();     return "Algorithm Format Encoded:" + key.getAlgorithm() + " - " + key.getFormat() + " - " + new String(key.getEncoded());   }       public void encrypt(InputStream in) throws InvalidKeyException, ShortBufferException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, IOException {     this.crypt(in, null, Cipher.ENCRYPT_MODE);   }       public String decrypt(InputStream in) throws InvalidKeyException, ShortBufferException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, IOException {     return this.crypt(in, Cipher.DECRYPT_MODE);   }       public void encrypt(InputStream in, OutputStream out) throws InvalidKeyException, ShortBufferException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, IOException {     this.crypt(in, out, Cipher.ENCRYPT_MODE);   }       public void decrypt(InputStream in, OutputStream out) throws InvalidKeyException, ShortBufferException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, IOException {     this.crypt(in, out, Cipher.DECRYPT_MODE);   }       public void crypt(InputStream in, OutputStream out, int mode) throws IOException, ShortBufferException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException {     Cipher cipher = Cipher.getInstance("AES");     cipher.init(mode, this.key);      int blockSize = cipher.getBlockSize();     int outputSize = cipher.getOutputSize(blockSize);     byte[] inBytes = new byte[blockSize];     byte[] outBytes = new byte[outputSize];      int inLength = 0;     boolean more = true;     while (more) {       inLength = in.read(inBytes);       if (inLength == blockSize) {  //只要输入数据块具有全长度（长度可被8整除），调用update方法         int outLength = cipher.update(inBytes, 0, blockSize, outBytes);         if (out != null) out.write(outBytes, 0, outLength);       } else {         more = false;       }     }     if (inLength > 0)  //不具有全长度，调用doFinal方法       outBytes = cipher.doFinal(inBytes, 0, inLength);     else       outBytes = cipher.doFinal();     if (out != null) {       out.write(outBytes);       out.flush();     }   }       public String crypt(InputStream in, int mode) throws IOException, ShortBufferException, IllegalBlockSizeException, BadPaddingException, NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException {     Cipher cipher = Cipher.getInstance("AES");     cipher.init(mode, this.key);      int blockSize = cipher.getBlockSize();     int outputSize = cipher.getOutputSize(blockSize);     byte[] inBytes = new byte[blockSize];     byte[] outBytes = new byte[outputSize];      int inLength = 0;     boolean more = true;     StringBuilder sb = new StringBuilder();     while (more) {       inLength = in.read(inBytes);       if (inLength == blockSize) {  //只要输入数据块具有全长度（长度可被8整除），调用update方法         int outLength = cipher.update(inBytes, 0, blockSize, outBytes);       } else {         more = false;       }     }     if (inLength > 0)  //不具有全长度，调用doFinal方法       outBytes = cipher.doFinal(inBytes, 0, inLength);     else       outBytes = cipher.doFinal();     sb.append(new String(outBytes));     return sb.toString();   }     public void setKey(Key key) {     this.key = key;   }    public Key getKey() {     return key;   } }