Apr 022015
 

Abstract

This software’s purpose is to warn you when a file gets corrupted and to help you find an uncorrupted version of this file among your backups.

It is not a Diff tool; there are already excellent and free Diff tools, such as KDiff3.

Preamble

Over time, data corrupts itself: optical discs oxidize, SSDs wear out, 0s and 1s get flipped…
The expected lifetime of data varies depending on the media but is usually taken to be around 10 years, provided you still have the machine and software to read it.

Therefore, how can you keep important photos, videos and documents?
Your only protection against data loss is multiple backups. Keep at least two backups of your important data, preferably in two different places. Copy the data every now and then to refresh the bits.
But having a backup is not useful if you cannot tell whether it is corrupted!

Hence this tool, the “Data Rot Detector”.

Download and Installation

  1. Download the following ZIP archive: DataRotDetector_1.0.0.1.zip
  2. Extract all the files from the ZIP in the same folder on your drive (keep the folder structure of the files in the ZIP).
  3. Run DRD.exe (if you are unsure whether to run the 64 bits or 32 bits version, try the 64 bits one first; if it does not work, use the 32 bits one).

Here is a suggested usage sequence

  1. Back up your files.
  2. After the backup, run the “Data Rot Detector” on the source drive, so that it can take a “thumbprint” of every file. This becomes the “original data set”.
  3. Immediately check the backup against the “original data set” (in case the backup failed silently).
  4. After some weeks (between backups), check your source drive against the “original data set”.
  5. If any file gets corrupted, retrieve the uncorrupted file by checking your backup and restore it to your main drive.

How does it work?

The “Data Rot Detector” calculates the MD5 of every file and keeps it along with the last modification date. If a file’s last modification date has not changed but its MD5 has, then it is considered to be corrupted.

Additional functions

Because of the way this program stores information, it can:

  • find moved or renamed files (between 2 scans)
  • find new and deleted files (between 2 scans)
  • find exact duplicates (even with different file names; sorted by size)

Requirements

  • At least Windows Vista and a NTFS drive
    (the “Data Rot Detector” could be recompiled for other systems since it uses Qt).
  • About 150 MiB of RAM for every 100k files.

 Limitations / False positives

The “Data Rot Detector”:

  • cannot tell if new or changed files are corrupted.
  • cannot test files it does not have access to, such as:
    • other users’ files
    • currently opened files (with share = none)
    • some system files
  • does not test unused space for corruption (use S.M.A.R.T. for this)
  • does not test alternate data streams (ADS)
  • can be misled by programs that lie about their files’ last modified date (e.g. for copy protection). Excel is unfortunately one such program (.xslx cannot be checked).

Support

I wrote this software for myself in my spare time. I offer no professional support, but I may answer questions posted in the Comments section of this blog.

License

The “Data Rot Detector” is published under the LGPL v2 license. The source code is included with the executable. If you use the code, I request that my name (Jonathan Mérel) appears in your credits. I make no warranty whatsoever about this program.

 

Apr 182011
 

How to choose a good password?
 
What is the minimum complexity for a password?
 
Why should you bother?

It is easy to hack most passwords

Hackers trying to get access to your computer, web account or bank account may use brute force attack to find your password. Brute force (and rainbow tables, see ophcrack), is when hackers try automatically every possible password: aaa, aab, aac…
 
With current computer speed it is easy to find passwords such as:
 

test in about 30 seconds
te4st in about 2 minutes
bf5gr# in about half an hour
bf5gr#2! in about a month

 
As you can see, the number of different types of characters and the length of the password are very important to protect yourself against brute force attacks.

The rules to create a strong password are:

 

Rule Bad Good
The length must be 9 characters or more bf5gr#2! bf5gr#2!!
Use every type of character (see table below) apassword 1Apassword!
Never use words that could be found in dictionaries, books, music, etc. (whatever the language) croissant 1Wfysovz!
Never use simple combinations of many simple words, words written backwards, etc. Monthy-nohtyP 1MPoyntthhoyn!

 
The different types of characters are:
 

Lower case letters abcdefghijklmnopqrstuvwxyz
Upper case letters ABCDEFGHIJKLMNOPQRSTUVWXYZ
Numbers 0123456789
Special characters !#$%^&*()-_+=  (and others you can type on your keyboard)

 
Also:
 

  • Never use the same password on different web sites. If one gets hacked, it will be easy for a hacker to access the other ones. A website may be hacked for many reasons beyond your control.
  • If you plan to use your account on public computers (cybercafe), change your password before leaving home and change it back when returning. Public computers may have key logger installed to record everything you type on your keyboard.
  • Put false passwords under your keyboard, in your wallet and in a file called “password” so that hackers try these false passwords and thus lock your account for too many trials. This concept is called “honeypot”.
  • Never post the answer to “secret questions” on social web sites such as Facebook. You don’t want a hacker to easily find the name of your first pet or the name of your mother.
  • If you are using Windows: disable the default Administrator and Guest accounts. These accounts are created by default and have no password.

 

OK, but how may I remember hundreds of different password???
They are so complicated!

 
A trick is to use the same password for every site by introducing small variations. For example let’s say you have chosen “p3A5t7a!e” as your main password, you may use “GMAIL p3A5t7a!e” and “FBOOKp3A5t7a!e” as passwords for Gmail and Facebook.
 

Apr 042011
 

More and more people have video (or photo) camera that can capture high resolution videos.

If you don’t own a Blu-ray burner but you have a DVD burner and a Blu-ray player, I have good news for you:

It is possible to put about 30 minutes of “Full HD” (1080p) video on a standard DVD. This type of DVD is called an AVCHD-DVD.

The best part: it is free!

Here are the easy steps to create your Full HD DVD using multiAVCHD:

  1. Produce some HD footage.
    • If you use Adobe Premiere CS5, export your video in H.264 (.mp4) using the HDTV preset.
    • Many formats are acceptable but, if you can, choose H.264 as it does offer the best quality.
  2. Download and install multiAVCHD  from here.
  3. Download and install ImgBurn from here.
    • Pay attention to refuse any third party offer such as the Ask! Toolbar.
  4. Launch “multiAVCHD” from the Windows Start menu.
  5. In the “settings” tab, check “Use ImgBurn”.
  6. Click on the “Add video files” button and choose your source video(s).
  7. Click on the “Start” button.
  8. Many output formats are available, choose “AVCHD for optical media → AVCHD (strict)” as it is the most compatible format across different brands of Blu-ray players.
  9. The processing could take a while if your video needs recompression, when it is finished ImgBurn should launch and burn the DVD automatically.
  10. Put your DVD in your home cinema Blu-ray player.

Voila!