iOS常用加密方法（aes、md5、base64）

1、AES加密
NSData+AES.h文件

[plain]  // 
//  NSData-AES.h 
//  Smile 
// 
//  Created by 周 敏 on 12-11-24. 
//  Copyright (c) 2012年 BOX. All rights reserved. 
// 
 
#import <Foundation/Foundation.h> 
 
@class NSString; 
 
@interface NSData (Encryption) 
 
- (NSData *)AES256EncryptWithKey:(NSString *)key;   //加密 
- (NSData *)AES256DecryptWithKey:(NSString *)key;   //解密 
 
@end 

NSData+AES.m文件
[plain]  // 
//  NSData-AES.h 
//  Smile 
// 
//  Created by 周 敏 on 12-11-24. 
//  Copyright (c) 2012年 BOX. All rights reserved. 
// 
 
#import "NSData+AES.h" 
#import <CommonCrypto/CommonCryptor.h> 
 
@implementation NSData (Encryption) 
 
- (NSData *)AES256EncryptWithKey:(NSString *)key {//加密 
    char keyPtr[kCCKeySizeAES256+1]; 
    bzero(keyPtr, sizeof(keyPtr)); 
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; 
    NSUInteger dataLength = [self length]; 
    size_t bufferSize = dataLength + kCCBlockSizeAES128; 
    void *buffer = malloc(bufferSize); 
    size_t numBytesEncrypted = 0; 
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, 
                                          kCCOptionPKCS7Padding | kCCOptionECBMode, 
                                          keyPtr, kCCBlockSizeAES128, 
                                          NULL, 
                                          [self bytes], dataLength, 
                                          buffer, bufferSize, 
                                          &numBytesEncrypted); 
    if (cryptStatus == kCCSuccess) { 
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted]; 
    } 
    free(buffer); 
    return nil; 
} 
 
 
- (NSData *)AES256DecryptWithKey:(NSString *)key {//解密 
    char keyPtr[kCCKeySizeAES256+1]; 
    bzero(keyPtr, sizeof(keyPtr)); 
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding]; 
    NSUInteger dataLength = [self length]; 
    size_t bufferSize = dataLength + kCCBlockSizeAES128; 
    void *buffer = malloc(bufferSize); 
    size_t numBytesDecrypted = 0; 
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, 
                                          kCCOptionPKCS7Padding | kCCOptionECBMode, 
                                          keyPtr, kCCBlockSizeAES128, 
                                          NULL, 
                                          [self bytes], dataLength, 
                                          buffer, bufferSize, 
                                          &numBytesDecrypted); 
    if (cryptStatus == kCCSuccess) { 
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted]; 
    } 
    free(buffer); 
    return nil; 
} 
 
@end 
這裡AES在iOS加過密以後以nsdata的形式存下來，如果想以nsstring形式存儲，那麼對nsdata進行base64位編碼。
2、BASE64編碼
首先下載GTMBase64文件，在工程中加入三個文件
GTMDefines.h
GTMBase64.h
GTMBase64.m
你可以在這裡找到這三個文件
http://code.google.com/p/google-toolbox-for-mac/source/browse/trunk/Foundation/?r=87
你也可以在下面的demo裡面找到這3個文件，demo會完整實現文章裡面常用的3種編碼方法。
我在此稍微封裝一下：

.h文件
[plain]   #pragma mark - base64 
+ (NSString*)encodeBase64String:(NSString *)input; 
+ (NSString*)decodeBase64String:(NSString *)input; 
+ (NSString*)encodeBase64Data:(NSData *)data; 
+ (NSString*)decodeBase64Data:(NSData *)data; 

.m文件
[plain]  #pragma mark - base64 
+ (NSString*)encodeBase64String:(NSString * )input {  
    NSData *data = [input dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];  
    data = [GTMBase64 encodeData:data];  
    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];  
    return base64String; 
} 
 
+ (NSString*)decodeBase64String:(NSString * )input {  
    NSData *data = [input dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];  
    data = [GTMBase64 decodeData:data];  
    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];  
    return base64String; 
}  
 
+ (NSString*)encodeBase64Data:(NSData *)data { 
    data = [GTMBase64 encodeData:data];  
    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease]; 
    return base64String; 
} 
 
+ (NSString*)decodeBase64Data:(NSData *)data { 
    data = [GTMBase64 decodeData:data];  
    NSString *base64String = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease]; 
    return base64String; 
} 

3、MD5加密
NSString+MD5.h文件
[plain]  // 
//  NSString+MD5Encrypt.h 
//  Smile 
// 
//  Created by 周 敏 on 12-11-24. 
//  Copyright (c) 2012年 BOX. All rights reserved. 
// 
 
#import <CommonCrypto/CommonDigest.h> 
 
@interface NSString (MD5) 
 
- (NSString *)md5Encrypt; 
 
@end 

NSString+MD5.m文件
[plain]  // 
//  NSString+MD5Encrypt.h 
//  Smile 
// 
//  Created by 周 敏 on 12-11-24. 
//  Copyright (c) 2012年 BOX. All rights reserved. 
// 
 
#import "NSString+MD5.h" 
 
@implementation NSString (MD5) 
 
- (NSString *)md5Encrypt { 
    const char *original_str = [self UTF8String]; 
    unsigned char result[CC_MD5_DIGEST_LENGTH]; 
    CC_MD5(original_str, strlen(original_str), result); 
    NSMutableString *hash = [NSMutableString string]; 
    for (int i = 0; i < 16; i++) 
        [hash appendFormat:@"%02X", result[i]]; 
    return [hash lowercaseString]; 
} 
 
@end