AES(The Advanced Encryption Standard)

AES是美国国家标准与技术研究所用于加密电子数据的规范。它被预期能成为人们公认的加密包括金融、电信和政府数字信息的方法

AES 是一个迭代的、对称密钥分组的密码,它可以使用128、192 和 256 位密钥,并且用 128 位(16字节)分组加密和解密数据。与公共密钥密码使用密钥对不同,对称密钥密码使用相同的密钥加密和解密数据。通过分组密码返回的加密数据 的位数与输入数据相同。迭代加密使用一个循环结构,在该循环中重复置换(permutations )和替换(substitutions)输入数据。

目前在商业App中使用的最多的是RSA与AES加密方式,两种加密各种所长,所幸目前都有接触过。

iOS中的使用

新建MySecurity类,继承于NSObject

.h文件


#import 

@interface MySecurity : NSObject

#pragma mark -根据密匙初始化
-(instancetype) initWithKey:(NSString *) key;

#pragma mark -加密
-(NSString *) AES256EncryptWithString:(NSString *) str;

#pragma mark -解密
-(NSString *) AES256DecryptWithString:(NSString *) str;

#pragma mark -获取安全密匙
+(NSString*) getSecurityKey;

@end

.m文件


#import "MySecurity.h"
#import "NSData+AES256.h"
#import "NSString+MD5.h"


@interface MySecurity ()
@property(strong,nonatomic) NSString *key;

@end

@implementation MySecurity


#pragma mark -获取安全钥匙
+(NSString*) getSecurityKey
{
    return @"加密的密匙";
}

#pragma mark -更加密码密匙初始化
-(instancetype) initWithKey:(NSString *) key
{
    self = [super init];
    if (self)
    {
        self.key = key;
    }
    return self;
}

#pragma mark -加密
-(NSString *) AES256EncryptWithString:(NSString *) str
{
    NSData *dt1 = [str dataUsingEncoding:NSUTF8StringEncoding];
 
    NSData *dt2 = [dt1 AES256EncryptWithKey:[self.key MD5]];
    
     NSString *str2 = [dt2 base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
    return str2;
}

#pragma mark -解密
-(NSString *) AES256DecryptWithString:(NSString *) str
{
    NSData *dt3 = [[NSData alloc] initWithBase64EncodedString:str options:NSDataBase64DecodingIgnoreUnknownCharacters];
    
    NSData *dt4 = [dt3 AES256DecryptWithKey:[self.key MD5]];
    
    NSString *str4 = [[NSString alloc] initWithData:dt4 encoding:NSUTF8StringEncoding];
    return str4;
}
 
@end
需要用到的NSData+AES256分类与NSString+MD5分类


//---------------NSData (AES256)头文件------------
#import 

@interface NSData (AES256)

/*
    加密
    (NSString*)key 32位秘钥
    返回加密后的 NSData
 */
- (NSData*)AES256EncryptWithKey:(NSString*)key ;

/*
 解密
 (NSString*)key 32位秘钥
 返回解密后的 NSData
 */
- (NSData*)AES256DecryptWithKey:(NSString*)key ;

@end



//---------------NSData (AES256)实现文件------------
#import "NSData+AES256.h"
#import 

@implementation NSData (AES256)


- (NSData*)AES256EncryptWithKey:(NSString*)key {
    
    char keyPtr[kCCKeySizeAES256 +1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    [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,
                                          kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes],
                                          dataLength, /* input */
                                          buffer,
                                          bufferSize, /* output */
                                          &numBytesEncrypted);
    
   
    
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }
    
    free(buffer);
    return nil;
}

- (NSData*)AES256DecryptWithKey:(NSString*)key {
    
    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];
    
    size_t bufferSize           = dataLength + kCCBlockSizeAES128;
    void* buffer                = malloc(bufferSize);
    
    size_t numBytesDecrypted    = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding|kCCOptionECBMode,
                                          keyPtr,
                                          kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes],
                                          dataLength, /* input */
                                          buffer,
                                          bufferSize, /* output */
                                          &numBytesDecrypted);
    
    if (cryptStatus == kCCSuccess) {
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
    }
    
    free(buffer); //free the buffer;
    return nil;
}

@end

//---------------NSString (MD5)头文件------------
#import 

@interface NSString (MD5)
/*
    获取字符串的MD5值
    返回32位MD5值
 */
-(NSString*) MD5;

@end

//---------------NSString (MD5)实现文件------------

#import "NSString+MD5.h"
#import 

@implementation NSString (MD5)

#pragma mark -MD5加密
-(NSString*) MD5
{
    const char * cStrValue = [self UTF8String];
    unsigned char theResult[CC_MD5_DIGEST_LENGTH];

    CC_MD5(cStrValue, (CC_LONG)strlen(cStrValue), theResult);
    return [NSString stringWithFormat:@"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
            theResult[0], theResult[1], theResult[2], theResult[3],
            theResult[4], theResult[5], theResult[6], theResult[7],
            theResult[8], theResult[9], theResult[10], theResult[11],
            theResult[12], theResult[13], theResult[14], theResult[15]];
}
 


@end
使用

//初始化对象
MySecurity *security = [[MySecurity alloc] initWithKey:[MySecurity getSecurityKey]];
//加密
NSString * str1 = [security AES256EncryptWithString:@"要加密的内容"];

//解密
NSString * str2 = [security AES256DecryptWithString:@"要解密的内容"];


总的来说,使用还是很简单的,希望能帮助到大家。

end