我应该在哪里调用Objective-c iOS应用程序中的计算函数？

Question

请原谅我对Objective-C的经验不足。我只玩了几个星期。

我想测试出苹果的加密和解密数据的方法（在这种情况下是一个NSString）。最终目标是让用户在文本区域输入内容，然后对其进行加密。

我使用Xcode的基本单视图应用和在这两个文件中加入（从here）：

NSDataEncryption.h

#import <Foundation/Foundation.h> 

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

和NSDataEncryption.m

#import "NSDataEncryption.h" 

#import <CommonCrypto/CommonCryptor.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 

基于this question，我打电话的方法是这样的：

#include "NSDataEncryption.h" 

//... 

NSString * key = @"ThisIsAKey"; 
    NSDataEncryption *encryptionClass = [[NSDataEncryption alloc] init]; //Errors: "Use of undeclared identfier 'encryptionClass'" and "Use of undeclared identifer 'NSDataEncryption'" 
    NSData * newData = [encryptionClass AES256EncryptionWithKey:key]; //Errors: "Use of undeclared identfier 'encryptionClass'" and "Use of undeclared identifer 'NSDataEncryption'" 

我试图把这里面的main（）和新的功能在里面另一个类（视图控制器）：

- (IBAction)someFunctionName { code here } 

大问题：为什么不接受Xcode中作为NSDataEncryption一类，也不会让我调用它的函数AES256EnryptionWithKey？我应该在应用程序的其他地方执行加密吗？

谢谢！

Answer 1

NSDataEncryption不是一个类。这是标准NSData类上的category。这意味着它使用两种方法'扩展'NSData类：- (NSData *)AES256EncryptWithKey:(NSString *)key;和- (NSData *)AES256DecryptWithKey:(NSString *)key;。这两个都返回NSData并将一个NSString作为参数。

你叫他们像这样：

NSData *dataToBeEncrypted = [NSData data]; //Put your data here 
NSString *key = @"ThisISAKEy"; 
NSData *newData = [dataToBeEncrypted AES256EncryptionWithKey:key]; 

您可以使用这些方法来加密/解密的字符串：

- (NSData*) encryptString:(NSString*)plaintext withKey:(NSString*)key { 
    return [[plaintext dataUsingEncoding:NSUTF8StringEncoding] AES256EncryptWithKey:key]; 

} 

- (NSString*) decryptData:(NSData*)ciphertext withKey:(NSString*)key { 
    return [[[NSString alloc] initWithData:[ciphertext AES256DecryptWithKey:key] 
            encoding:NSUTF8StringEncoding] autorelease]; 
} 

Answer 2

NSData *data = [myString dataUsingEncoding:NSUTF8StringEncoding]; 
NSData *encrypted = [data AES256EncryptionWithKey:@"RandomString"];