9、Android与IOS通用AES加密解密方法

1、Android

（1）加密类，Base64Encoder.java

package com.example.aes256;import java.io.*;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;/**** Constructs a new Base64 encoder that writes output to the given* OutputStream.** @param out the output stream*/public Base64Encoder(OutputStream out) { super(out);}/**** 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 <[e-mail]> 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 (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.  The encoder* uses the ISO-8859-1 (Latin-1) encoding to convert the string to bytes.* For greater control over the encoding, encode the string to bytes* yourself and use encode(byte[]).** @param unencoded the string to encode* @return the encoded form of the unencoded string*/public static String encode(String unencoded) { byte[] bytes = null; try {   bytes = unencoded.getBytes("UTF-8"); } catch (UnsupportedEncodingException ignored) { } return encode(bytes);}/**** Returns the encoded form of the given unencoded string.** @param bytes the bytes to encode* @return the encoded form of the unencoded string*/public static String encode(byte[] bytes) { ByteArrayOutputStream out =    new ByteArrayOutputStream((int) (bytes.length * 1.37)); Base64Encoder encodedOut = new Base64Encoder(out);  try {   encodedOut.write(bytes);   encodedOut.close();   return out.toString("UTF-8"); } catch (IOException ignored) { return null; }}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(); }}}

（2）解密类Base64Decoder.java

package com.example.aes256;import java.io.*;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 integersprivate 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*/public 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) { 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 = null; try {   bytes = encoded.getBytes("UTF-8"); } catch (UnsupportedEncodingException ignored) { } Base64Decoder in = new Base64Decoder(                    new ByteArrayInputStream(bytes));  ByteArrayOutputStream out =    new ByteArrayOutputStream((int) (bytes.length * 0.67)); try {   byte[] buf = new byte[4 * 1024];  // 4K buffer   int bytesRead;   while ((bytesRead = in.read(buf)) != -1) {     out.write(buf, 0, bytesRead);   }   out.close();   return out.toByteArray(); } catch (IOException ignored) { return null; }}public static void main(String[] args) throws Exception { if (args.length != 1) {   System.err.println("Usage: java Base64Decoder fileToDecode");   return; } Base64Decoder decoder = null; try {   decoder = new Base64Decoder(             new BufferedInputStream(             new FileInputStream(args[0])));   byte[] buf = new byte[4 * 1024];  // 4K buffer   int bytesRead;   while ((bytesRead = decoder.read(buf)) != -1) {     System.out.write(buf, 0, bytesRead);   } } finally {   if (decoder != null) decoder.close(); }}}

（3）封装类，AES.java。用于调用加密解密类

package com.example.aes256;/** *  LICENSE AND TRADEMARK NOTICES *   *  Except where noted, sample source code written by Motorola Mobility Inc. and *  provided to you is licensed as described below. *   *  Copyright (c) 2012, Motorola, Inc. *  All  rights reserved except as otherwise explicitly indicated. * *  Redistribution and use in source and binary forms, with or without *  modification, are permitted provided that the following conditions are met: * *  - Redistributions of source code must retain the above copyright notice, *  this list of conditions and the following disclaimer. * *  - Redistributions in binary form must reproduce the above copyright notice, *  this list of conditions and the following disclaimer in the documentation *  and/or other materials provided with the distribution. * *  - Neither the name of Motorola, Inc. nor the names of its contributors may *  be used to endorse or promote products derived from this software without *  specific prior written permission. * *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS *  INTERRUPTION) HOWEVER  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE *  POSSIBILITY OF SUCH DAMAGE. *   *  Other source code displayed may be licensed under Apache License, Version *  2. *   *  Copyright © 2012, Android Open Source Project. All rights reserved unless *  otherwise explicitly indicated. *   *  Licensed under the Apache License, Version 2.0 (the "License"); you may not *  use this file except in compliance with the License. You may obtain a copy *  of the License at *   *  http://www.apache.org/licenses/LICENSE-2.0. *   *  Unless required by applicable law or agreed to in writing, software *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the *  License for the specific language governing permissions and limitations *  under the License. *   */// Please refer to the accompanying article at // http://developer.motorola.com/docs/using_the_advanced_encryption_standard_in_android/// A tutorial guide to using AES encryption in Android// First we generate a 256 bit secret key; then we use that secret key to AES encrypt a plaintext message.// Finally we decrypt the ciphertext to get our original message back.// We don't keep a copy of the secret key - we generate the secret key whenever it is needed, // so we must remember all the parameters needed to generate it -// the salt, the IV, the human-friendly passphrase, all the algorithms and parameters to those algorithms.// Peter van der Linden, April 15 2012import java.io.UnsupportedEncodingException;import java.security.InvalidAlgorithmParameterException;import java.security.InvalidKeyException;import java.security.NoSuchAlgorithmException;import java.security.spec.InvalidKeySpecException;import javax.crypto.BadPaddingException;import javax.crypto.Cipher;import javax.crypto.IllegalBlockSizeException;import javax.crypto.NoSuchPaddingException;import javax.crypto.SecretKey;import javax.crypto.SecretKeyFactory;import javax.crypto.spec.IvParameterSpec;import javax.crypto.spec.PBEKeySpec;import javax.crypto.spec.SecretKeySpec;import android.util.Log;public class AES {// private final String KEY_GENERATION_ALG = "PBEWITHSHAANDTWOFISH-CBC";private final String KEY_GENERATION_ALG = "PBKDF2WithHmacSHA1";private final int HASH_ITERATIONS = 10000;private final int KEY_LENGTH = 256;private char[] humanPassphrase = { 'P', 'e', 'r', ' ', 'v', 'a', 'l', 'l','u', 'm', ' ', 'd', 'u', 'c', 'e', 's', ' ', 'L', 'a', 'b', 'a','n', 't' };// char[] humanPassphrase = { 'v', 't', 'i', 'o', 'n','s','f','o','t', '.',// 'c', 'o', 'm',// 'p'};private byte[] salt = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0xA, 0xB, 0xC, 0xD,0xE, 0xF }; // must save this for next time we want the keyprivate PBEKeySpec myKeyspec = new PBEKeySpec(humanPassphrase, salt,HASH_ITERATIONS, KEY_LENGTH);private final String CIPHERMODEPADDING = "AES/CBC/PKCS7Padding";private SecretKeyFactory keyfactory = null;private SecretKey sk = null;private SecretKeySpec skforAES = null;private byte[] iv = { 0xA, 1, 0xB, 5, 4, 0xF, 7, 9, 0x17, 3, 1, 6, 8, 0xC,0xD, 91 };private IvParameterSpec IV;public AES() {try {keyfactory = SecretKeyFactory.getInstance(KEY_GENERATION_ALG);sk = keyfactory.generateSecret(myKeyspec);} catch (NoSuchAlgorithmException nsae) {Log.e("AESdemo","no key factory support for PBEWITHSHAANDTWOFISH-CBC");} catch (InvalidKeySpecException ikse) {Log.e("AESdemo", "invalid key spec for PBEWITHSHAANDTWOFISH-CBC");}// This is our secret key. We could just save this to a file instead of// regenerating it// each time it is needed. But that file cannot be on the device (too// insecure). It could// be secure if we kept it on a server accessible through https.byte[] skAsByteArray = sk.getEncoded();// Log.d("",// "skAsByteArray=" + skAsByteArray.length + ","// + Base64Encoder.encode(skAsByteArray));skforAES = new SecretKeySpec(skAsByteArray, "AES");;IV = new IvParameterSpec(iv);}public String encrypt(byte[] plaintext) {byte[] ciphertext = encrypt(CIPHERMODEPADDING, skforAES, IV, plaintext);String base64_ciphertext = Base64Encoder.encode(ciphertext);return base64_ciphertext;}public String decrypt(String ciphertext_base64) {byte[] s = Base64Decoder.decodeToBytes(ciphertext_base64);String decrypted = new String(decrypt(CIPHERMODEPADDING, skforAES, IV,s));return decrypted;}// Use this method if you want to add the padding manually// AES deals with messages in blocks of 16 bytes.// This method looks at the length of the message, and adds bytes at the end// so that the entire message is a multiple of 16 bytes.// the padding is a series of bytes, each set to the total bytes added (a// number in range 1..16).private byte[] addPadding(byte[] plain) {byte plainpad[] = null;int shortage = 16 - (plain.length % 16);// if already an exact multiple of 16, need to add another block of 16// bytesif (shortage == 0)shortage = 16;// reallocate array bigger to be exact multiple, adding shortage bits.plainpad = new byte[plain.length + shortage];for (int i = 0; i < plain.length; i++) {plainpad[i] = plain[i];}for (int i = plain.length; i < plain.length + shortage; i++) {plainpad[i] = (byte) shortage;}return plainpad;}// Use this method if you want to remove the padding manually// This method removes the padding bytesprivate byte[] dropPadding(byte[] plainpad) {byte plain[] = null;int drop = plainpad[plainpad.length - 1]; // last byte gives number of// bytes to drop// reallocate array smaller, dropping the pad bytes.plain = new byte[plainpad.length - drop];for (int i = 0; i < plain.length; i++) {plain[i] = plainpad[i];plainpad[i] = 0; // don't keep a copy of the decrypt}return plain;}private byte[] encrypt(String cmp, SecretKey sk, IvParameterSpec IV,byte[] msg) {try {Cipher c = Cipher.getInstance(cmp);c.init(Cipher.ENCRYPT_MODE, sk, IV);return c.doFinal(msg);} catch (NoSuchAlgorithmException nsae) {Log.e("AESdemo", "no cipher getinstance support for " + cmp);} catch (NoSuchPaddingException nspe) {Log.e("AESdemo", "no cipher getinstance support for padding " + cmp);} catch (InvalidKeyException e) {Log.e("AESdemo", "invalid key exception");} catch (InvalidAlgorithmParameterException e) {Log.e("AESdemo", "invalid algorithm parameter exception");} catch (IllegalBlockSizeException e) {Log.e("AESdemo", "illegal block size exception");} catch (BadPaddingException e) {Log.e("AESdemo", "bad padding exception");}return null;}private byte[] decrypt(String cmp, SecretKey sk, IvParameterSpec IV,byte[] ciphertext) {try {Cipher c = Cipher.getInstance(cmp);c.init(Cipher.DECRYPT_MODE, sk, IV);return c.doFinal(ciphertext);} catch (NoSuchAlgorithmException nsae) {Log.e("AESdemo", "no cipher getinstance support for " + cmp);} catch (NoSuchPaddingException nspe) {Log.e("AESdemo", "no cipher getinstance support for padding " + cmp);} catch (InvalidKeyException e) {Log.e("AESdemo", "invalid key exception");} catch (InvalidAlgorithmParameterException e) {Log.e("AESdemo", "invalid algorithm parameter exception");} catch (IllegalBlockSizeException e) {Log.e("AESdemo", "illegal block size exception");} catch (BadPaddingException e) {Log.e("AESdemo", "bad padding exception");e.printStackTrace();}return null;}}

（4）使用类

package com.example.aes256;import java.io.UnsupportedEncodingException;import android.os.Bundle;import android.app.Activity;import android.graphics.YuvImage;public class MainActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);AES gAes = new AES();String sendString="欢迎，Hello World！";byte[] sendBytes = null;try {sendBytes = sendString .getBytes("UTF8");} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.printStackTrace();}String str = gAes.encrypt(sendBytes);System.out.println(str);String result = gAes.decrypt(str);System.out.println(result);}}

（5）结果

2、IOS

（1）加密解密类

NSData+AES256.h

#import <Foundation/Foundation.h>#import <CommonCrypto/CommonCryptor.h>#import <CommonCrypto/CommonKeyDerivation.h>@interface NSData (AES256)+ (NSString *)AES256EncryptWithPlainText:(NSString *)plain;        /*加密方法,参数需要加密的内容*/+ (NSString *)AES256DecryptWithCiphertext:(NSString *)ciphertexts; /*解密方法，参数数密文*/@end

NSData+AES256.m

////  NSData+AES256.m//  AES////  Created by Henry Yu on 2009/06/03.//  Copyright 2010 Sevensoft Technology Co., Ltd.(http://www.sevenuc.com)//  All rights reserved.////  Permission is given to use this source code file, free of charge, in any//  project, commercial or otherwise, entirely at your risk, with the condition//  that any redistribution (in part or whole) of source code must retain//  this copyright and permission notice. Attribution in compiled projects is//  appreciated but not required.//#import "NSData+AES256.h"#define PASSWORD @"Per vallum duces Labant"static const char encodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";const NSUInteger kAlgorithmKeySize = kCCKeySizeAES256;const NSUInteger kPBKDFRounds = 10000;  // ~80ms on an iPhone 4static Byte saltBuff[] = {0,1,2,3,4,5,6,7,8,9,0xA,0xB,0xC,0xD,0xE,0xF};static Byte ivBuff[]   = {0xA,1,0xB,5,4,0xF,7,9,0x17,3,1,6,8,0xC,0xD,91};@implementation NSData (AES256)+ (NSData *)AESKeyForPassword:(NSString *)password{                  //Derive a key from a text password/passphrase        NSMutableData *derivedKey = [NSMutableData dataWithLength:kAlgorithmKeySize];        NSData *salt = [NSData dataWithBytes:saltBuff length:kCCKeySizeAES128];        int result = CCKeyDerivationPBKDF(kCCPBKDF2,        // algorithm算法                                  password.UTF8String,  // password密码                                  password.length,      // passwordLength密码的长度                                  salt.bytes,           // salt内容                                  salt.length,          // saltLen长度                                  kCCPRFHmacAlgSHA1,    // PRF                                  kPBKDFRounds,         // rounds循环次数                                  derivedKey.mutableBytes, // derivedKey                                  derivedKey.length);   // derivedKeyLen derive:出自        NSAssert(result == kCCSuccess,             @"Unable to create AES key for spassword: %d", result);    return derivedKey;}/*加密方法*/+ (NSString *)AES256EncryptWithPlainText:(NSString *)plain {    NSData *plainText = [plain dataUsingEncoding:NSUTF8StringEncoding];// 'key' should be 32 bytes for AES256, will be null-padded otherwisechar keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)        NSUInteger dataLength = [plainText length];size_t bufferSize = dataLength + kCCBlockSizeAES128;void *buffer = malloc(bufferSize);    bzero(buffer, sizeof(buffer));size_t numBytesEncrypted = 0;    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,kCCOptionPKCS7Padding,                                          [[NSData AESKeyForPassword:PASSWORD] bytes], kCCKeySizeAES256,  ivBuff /* initialization vector (optional) */,  [plainText bytes], dataLength, /* input */  buffer, bufferSize, /* output */  &numBytesEncrypted);if (cryptStatus == kCCSuccess) {        NSData *encryptData = [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];return [encryptData base64Encoding];}free(buffer); //free the buffer;return nil;}/*解密方法*/+ (NSString *)AES256DecryptWithCiphertext:(NSString *)ciphertexts{        NSData *cipherData = [NSData dataWithBase64EncodedString:ciphertexts];// 'key' should be 32 bytes for AES256, will be null-padded otherwisechar keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)    NSUInteger dataLength = [cipherData length];size_t bufferSize = dataLength + kCCBlockSizeAES128;void *buffer = malloc(bufferSize);    size_t numBytesDecrypted = 0;CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,  [[NSData AESKeyForPassword:PASSWORD] bytes], kCCKeySizeAES256,   ivBuff ,/* initialization vector (optional) */  [cipherData bytes], dataLength, /* input */  buffer, bufferSize, /* output */  &numBytesDecrypted);if (cryptStatus == kCCSuccess) {        NSData *encryptData = [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];return [[[NSString alloc] initWithData:encryptData encoding:NSUTF8StringEncoding] init];}free(buffer); //free the buffer;return nil;}+ (id)dataWithBase64EncodedString:(NSString *)string;{    if (string == nil)        [NSException raise:NSInvalidArgumentException format:nil];    if ([string length] == 0)        return [NSData data];        static char *decodingTable = NULL;    if (decodingTable == NULL)    {        decodingTable = malloc(256);        if (decodingTable == NULL)            return nil;        memset(decodingTable, CHAR_MAX, 256);        NSUInteger i;        for (i = 0; i < 64; i++)            decodingTable[(short)encodingTable[i]] = i;    }        const char *characters = [string cStringUsingEncoding:NSASCIIStringEncoding];    if (characters == NULL)     //  Not an ASCII string!        return nil;    char *bytes = malloc((([string length] + 3) / 4) * 3);    if (bytes == NULL)        return nil;    NSUInteger length = 0;        NSUInteger i = 0;    while (YES)    {        char buffer[4];        short bufferLength;        for (bufferLength = 0; bufferLength < 4; i++)        {            if (characters[i] == '\0')                break;            if (isspace(characters[i]) || characters[i] == '=')                continue;            buffer[bufferLength] = decodingTable[(short)characters[i]];            if (buffer[bufferLength++] == CHAR_MAX)      //  Illegal character!            {                free(bytes);                return nil;            }        }                if (bufferLength == 0)            break;        if (bufferLength == 1)      //  At least two characters are needed to produce one byte!        {            free(bytes);            return nil;        }                //  Decode the characters in the buffer to bytes.        bytes[length++] = (buffer[0] << 2) | (buffer[1] >> 4);        if (bufferLength > 2)            bytes[length++] = (buffer[1] << 4) | (buffer[2] >> 2);        if (bufferLength > 3)            bytes[length++] = (buffer[2] << 6) | buffer[3];    }        bytes = realloc(bytes, length);    return [NSData dataWithBytesNoCopy:bytes length:length];}- (NSString *)base64Encoding;{    if ([self length] == 0)        return @"";        char *characters = malloc((([self length] + 2) / 3) * 4);    if (characters == NULL)        return nil;    NSUInteger length = 0;        NSUInteger i = 0;    while (i < [self length])    {        char buffer[3] = {0,0,0};        short bufferLength = 0;        while (bufferLength < 3 && i < [self length])            buffer[bufferLength++] = ((char *)[self bytes])[i++];                //  Encode the bytes in the buffer to four characters, including padding "=" characters if necessary.        characters[length++] = encodingTable[(buffer[0] & 0xFC) >> 2];        characters[length++] = encodingTable[((buffer[0] & 0x03) << 4) | ((buffer[1] & 0xF0) >> 4)];        if (bufferLength > 1)            characters[length++] = encodingTable[((buffer[1] & 0x0F) << 2) | ((buffer[2] & 0xC0) >> 6)];        else characters[length++] = '=';        if (bufferLength > 2)            characters[length++] = encodingTable[buffer[2] & 0x3F];        else characters[length++] = '=';        }        return [[[NSString alloc] initWithBytesNoCopy:characters length:length encoding:NSASCIIStringEncoding freeWhenDone:YES] init];}@end

（2）使用

- (void)viewDidLoad{    [super viewDidLoad];        NSString* message = @"欢迎，Hello World！";        NSString* str = [NSData AES256EncryptWithPlainText:message];    NSString* res = [NSData AES256DecryptWithCiphertext:str];    NSLog(@"%@",str);    NSLog(@"%@",res);// Do any additional setup after loading the view, typically from a nib.}

（3）结果