iPhone开发之AES加密和解密

参考来自：http://zhiwei.li/text/2011/07/iphone%E4%B8%8Aaes%E5%8A%A0%E5%AF%86%E7%9A%84%E5%AE%9E%E7%8E%B0/

头文件 NSDataEncryption.h

#import <UIKit/UIKit.h>

@interface NSData (AES256)
- (NSData *)AES256EncryptWithKey:(NSString *)key;//加密
- (NSData *)AES256DecryptWithKey:(NSString *)key;//解密
@end

实现 NSDataEncryption.m

#import "NSDataEncryption.h"
#import <CommonCrypto/CommonDigest.h>
#import <CommonCrypto/CommonCryptor.h>
#import <CommonCrypto/CommonHMAC.h>

@implementation NSData (AES256)
- (NSData *)AES256EncryptWithKey:(NSString *)key {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    
    //See the doc: For block ciphers, the output size will always be less than or
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    
    free(buffer); //free the buffer;
    return nil;
}

- (NSData *)AES256DecryptWithKey:(NSString *)key {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    
    //See the doc: For block ciphers, the output size will always be less than or
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesDecrypted);
    
    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
    }
    
    free(buffer); //free the buffer;
    return nil;
}

@end

使用方法：

NSString *key = @"my password";//密码
    NSString *secret = @"text to encrypt";//要加密的文本
    
    //加密过程
    NSData *plain = [secret dataUsingEncoding:NSUTF8StringEncoding]; //NSString转为NSData
    NSData *cipher = [plain AES256EncryptWithKey:key];//ASE加密后的密码
    printf("%s\n", [[cipher description] UTF8String]);//输出secret通过key后的AES加密内容
    
    
    //解密过程
    plain = [cipher AES256DecryptWithKey:key];//对cipher进行解密
    printf("%s\n", [[plain description] UTF8String]);
    printf("%s\n", [[[NSString alloc] initWithData:plain encoding:NSUTF8StringEncoding] UTF8String]);

开源项目参考：https://github.com/AlanQuatermain/aqtoolkit/tree/master/CommonCrypto/