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FAQ on the xz-utils backdoor

Background

On March 29th, 2024, a backdoor was discovered in xz-utils, a suite of software that gives developers lossless compression. This package is commonly used for compressing release tarballs, software packages, kernel images, and initramfs images. It is very widely distributed, statistically your average Linux or macOS system will have it installed for

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class EnumExample {
    private enum Status {
        Init, Success, Failed, Loading
    }
    
    public static enum ProcessStatus {
        LOAD_STAGE(Status.Init),
        
        END_STAGE(Status.Failed);
        

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private fun hopAnimation() {
        val animation = bottomContainer
            .animate()
            .translationYBy(-40f)
            .alpha(0.9f)
            .setDuration(400)
        animation.withEndAction {
            bottomContainer
                .animate()
                .alpha(0.5f)

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// Generate data
int arraySize = 32768;
int data[] = new int[arraySize];

Random rnd = new Random(0);
for (int c = 0; c < arraySize; ++c)
    data[c] = rnd.nextInt() % 256;

// notice !!!
Arrays.sort(data);

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public class PhotoMultipartRequest<T> extends Request<T> {


private static final String FILE_PART_NAME = "file";

    private MultipartEntityBuilder mBuilder = MultipartEntityBuilder.create();
    private final Response.Listener<T> mListener;
    private final File mImageFile;
    protected Map<String, String> headers;

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public static int getMaxCodecInstanceByName(String name) {
    final Vector<MediaCodec> codecs = new Vector<>();
    final MediaFormat format = MediaFormat.createVideoFormat(MIME_TYPE, 1920, 1080);
    MediaCodec codec = null;

    for (int i = 0; i < max; i++) {
        try {
            codec = MediaCodec.createDecoderByType(MediaFormat.MIMETYPE_VIDEO_AVC);
            codec.configure(format, null, null, 0);
            codec.start();

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/**
 http://mythosil.hatenablog.com/entry/20111017/1318873155
 http://blog.dealforest.net/2012/03/ios-android-per-aes-crypt-connection/
 */

@interface NSData (AES)

- (NSData *)AES128EncryptedDataWithKey:(NSString *)key;
- (NSData *)AES128DecryptedDataWithKey:(NSString *)key;
- (NSData *)AES128EncryptedDataWithKey:(NSString *)key iv:(NSString *)iv;

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// consider about this url : http://sylvana.net/jpegcrop/exif_orientation.html
// you might consider when you get your image's exif information, 
// check the orientation tag, it usually is 1, 3, 6, 8
// So, rotate it.


BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(path, options);

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import android.text.format.DateUtils;
import android.util.FloatMath;


public class TwilightCalculator {
    /** Value of {@link #mState} if it is currently day */
    public static final int DAY = 0;
    /** Value of {@link #mState} if it is currently night */
    public static final int NIGHT = 1;
    private static final float DEGREES_TO_RADIANS = (float) (Math.PI / 180.0f);

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[Isolating Differences Between Files][paper]

Advantage over Other Algorithms

The diff output is more specific:

[I]f a whole block of text is moved, then all of it, rather than just the beginning and end, is detected as changed.

>The algorithm described here avoids these difficulties. It detects differences that correspond very closely to our intuitive notion of difference.