IOS上的图像加密/解密

Question

我们正在使用加密/解密和 UIIMAGE。如果我们在不保存到 iphone 库中的情况下加密和解密和 UIIMAge，它可以正常工作，但如果我们加密、保存到库中、加载（加密的图像）到应用程序中并解密它就不好了。

我们正在使用这个函数来加密/解密/保存/加载

//加密

UIImage *image = self.imageView.image;
CGContextRef ctx;
CGImageRef imageRef = [image CGImage];
NSUInteger width = CGImageGetWidth(imageRef);
NSUInteger height = CGImageGetHeight(imageRef);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = malloc(height * width * 4);
int valor =(height * width * 4);
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                             bitsPerComponent, bytesPerRow, colorSpace,
                                             kCGImageAlphaPremultipliedLast |    kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);

CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(context);


    NSData *data = [NSData dataWithBytes:(const void *)rawData length:sizeof(unsigned char)*valor];
   NSData *encryptedData  = [data AES256EncryptWithKey:@"\"thisIsASecre"];


rawData = [encryptedData bytes];


NSData *dataData2 = [NSData dataWithBytes:rawData length:sizeof(rawData)];

ctx = CGBitmapContextCreate(rawData,
                            CGImageGetWidth( imageRef ),
                            CGImageGetHeight( imageRef ),
                            8,
                            CGImageGetBytesPerRow( imageRef ),
                            CGImageGetColorSpace( imageRef ),
                            kCGImageAlphaPremultipliedLast );

imageRef = CGBitmapContextCreateImage (ctx);
UIImage *rawImage = [UIImage imageWithCGImage:imageRef];

self.imageView.image = rawImage;

UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);

CGContextRelease(ctx);

//解密

UIImage *image = self.imageView.image;
CGContextRef ctx;
CGImageRef imageRef = [image CGImage];
NSUInteger width = CGImageGetWidth(imageRef);
NSUInteger height = CGImageGetHeight(imageRef);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = malloc(height * width * 4);
int valor =(height * width * 4);
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(rawData, width, height,
                                             bitsPerComponent, bytesPerRow, colorSpace,
                                             kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);

CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(context);


   NSData *data = [NSData dataWithBytes:(const void *)rawData length:sizeof(unsigned char)*valor];
   NSData *encryptedData  = [data AES256DecryptWithKey:@"\"thisIsASecre"];


rawData = [encryptedData bytes];




ctx = CGBitmapContextCreate(rawData,
                            CGImageGetWidth( imageRef ),
                            CGImageGetHeight( imageRef ),
                            8,
                            CGImageGetBytesPerRow( imageRef ),
                            CGImageGetColorSpace( imageRef ),
                            kCGImageAlphaPremultipliedLast );

imageRef = CGBitmapContextCreateImage (ctx);
UIImage *rawImage = [UIImage imageWithCGImage:imageRef];

self.imageView.image = rawImage;
image = rawImage;

    UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);

CGContextRelease(ctx);

// 加载图片

UIImagePickerController *picker = [[UIImagePickerController alloc] init];
picker.delegate = self;
picker.allowsEditing = YES;

picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;


[self presentViewController:picker animated:YES completion:NULL];


- (void)imagePickerController:(UIImagePickerController *)picker   didFinishPickingMediaWithInfo:(NSDictionary *)info {

self.imageView.image = [info objectForKey:@"UIImagePickerControllerOriginalImage"]; 

[picker dismissViewControllerAnimated:YES completion:NULL];


}

//还有我用来加密/解密的类

- (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;
}

有人知道是什么问题吗？

谢谢！

Answer 1

如果您将位图图像保存到照片库，它会以 JPG 格式存储。 JPG 的有损格式将完全覆盖您的加密过程。尝试将您的位图图像转换为 PNG 图像，然后保存：

UIImage* pngImage = [UIImage imageWithData:UIImagePNGRepresentation(rawImage)];
UIImageWriteToSavedPhotosAlbum(pngImage, nil, nil, NULL);