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Foolishly Underestim Group

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Extreme Code Cracker


Members of Cornell's Global Positioning System (GPS) Laboratory have cracked the so-called pseudo random number (PRN) codes of Europe's first global navigation satellite, despite efforts to keep the codes secret. That means free access for consumers who use navigation devices -- including handheld receivers and systems installed in vehicles -- that need PRNs to listen to satellites.




Extreme Code Cracker



Because GPS satellites, which were put into orbit by the Department of Defense, are funded by U.S. taxpayers, the signal is free -- consumers need only purchase a receiver. Galileo, on the other hand, must make money to reimburse its investors -- presumably by charging a fee for PRN codes. Because Galileo and GPS will share frequency bandwidths, Europe and the United States signed an agreement whereby some of Galileo's PRN codes must be "open source." Nevertheless, after broadcasting its first signals on Jan. 12, 2006, none of GIOVE-A's codes had been made public.


In mid-January, Mark Psiaki, professor of mechanical and aerospace engineering at Cornell and co-leader of Cornell's GPS Laboratory, requested the codes from Martin Unwin at Surrey Satellite Technology Ltd., one of three privileged groups in the world with the PRN codes.


"In a very polite way, he said, 'Sorry, goodbye,'" recalled Psiaki. Next Psiaki contacted Oliver Montenbruck, a friend and colleague in Germany, and discovered that he also wanted the codes. "Even Europeans were being frustrated," said Psiaki. "Then it dawned on me: Maybe we can pull these things off the air, just with an antenna and lots of signal processing."


Within one week Psiaki's team developed a basic algorithm to extract the codes. Two weeks later they had their first signal from the satellite, but were thrown off track because the signal's repeat period was twice that expected. By mid-March they derived their first estimates of the code, and -- with clever detective work and an important tip from Montenbruck -- published final versions on their Web site ( ) on April 1. Two days later, NovAtel Inc., a Canadian-based major manufacturer of GPS receivers, downloaded the codes from the Web site in a few minutes and soon afterward began tracking GIOVE-A for the first time.


Galileo eventually published PRN codes in mid-April, but they weren't the codes currently used by the GIOVE-A satellite. Furthermore, the same publication labeled the open source codes as intellectual property, claiming a license is required for any commercial receiver. "That caught my eye right away," said Psiaki. "Apparently they were trying to make money on the open source code."


Afraid that cracking the code might have been copyright infringement, Psiaki's group sought outside advice. "We were told that cracking the encryption of creative content, like music or a movie, is illegal, but the encryption used by a navigation signal is fair game," said Psiaki. The upshot: The Europeans cannot copyright basic data about the physical world, even if the data are coming from a satellite that they built.


Does the technique that Shawn Lane used in his fastest playing with the edge of the pick so extreme that the angle of the pick is negligible? Here he is talking about how he pretty much hols the pick straight up and down as he traverses the strings. He covers this at the 59 second mark.


An extreme heat event is several days or more with uncommonly hot temperatures that can be harmful to people. Climate change will make extreme heat events more common, especially in cities. New Orleans will have warmer temperatures during the year. Illnesses and deaths caused by extreme heat events are preventable.


Simple Mills is initiating a voluntary recall because a select number of Fine Ground Sea Salt Almond Flour Cracker boxes were erroneously packed with bags of Farmhouse Cheddar Almond Flour Crackers. As a result, the packaging does not list the presence of a possible allergen (milk). Some people who have an extreme allergy or severe sensitivity to milk could run the risk of a serious or lifethreatening allergic reaction if they consume this product.


Recalled product could have been sold as an individual box or part of a 3 or 6 pack of 4.25 oz boxes. On individual boxes, the lot code (Best By date) can be found on the top of each box and the item number (UPC) can be found on the bottom of each box. Photos of the packaging of the recalled product are below.


With its sleek, black packaging and transparently "extreme" (or maybe just "xtreme") marketing slant, Cracker Jack'D is a self-parody that's almost too easy to make fun of. Its life cycle, which should play out over the course of the next year or so, will probably look something like this: an annoyingly intense but gratifyingly short ad campaign; a cringe-worthy cross-promotion with a wildly inappropriate brand (Red Bull, perhaps?); an embarrassing tweet from one of the rap stars who were brought in to endorse the product, leading to a hastily issued corporate apology; and then a quick plummet into the black hole of product failures. By 2016 nobody will even remember Cracker Jack'D existed; by 2018 it should start showing up in "What Were They Thinking?" slideshows.


You can manually try different passwords as ZIP files come with unlimited attempts, but this process is extremely tedious. Also, you may never remember a forgotten password even after hundreds of shots. Using a ZIP password recovery tool is the easiest way of decompressing ZIP files after losing their passwords.


I used to think that being able to think, code, and communicate simultaneously was an impossible feat, until I realized that most people are just not good at coding interviews when they first start out. Interviewing is a skill that you can get better at by studying, preparing, and practicing for it.


Java is a decent choice too. But because you will have to constantly declare types in your code, it means entering extra keystrokes. This will slow down the speed at which you code and type. This issue will be more apparent when you have to write on a whiteboard during on-site interviews.


Practice and solve algorithm questions in your chosen language. While Cracking the Coding Interview is a good resource, I prefer solving problems by typing code, letting it run, and getting instant feedback.


After completing a question on LeetCode, I usually add the time and space complexities of the written code as comments above the function body. I use the comments to remind myself to communicate the analysis of the algorithm after I have completed the implementation.


Congratulations, you are ready to put your skills to practice! In a coding interview, you will be given a technical question by the interviewer. You will write the code in a real-time, collaborative editor (phone screen) or on a whiteboard (on-site), and have 30 to 45 minutes to solve the problem. This is where the real fun begins!


Your interviewer will be looking to see that you meet the requirements of the role. It is up to you to show them that you have the skills. Initially, it may feel weird to talk while you code, as most programmers do not make a habit of explaining out loud their thoughts while they are typing code.


However, it is hard for the interviewer to know what you are thinking by just looking at your code. If you communicate your approach to the interviewer even before you start to code, you can validate your approach with them. This way, the two of you can agree on an acceptable approach.


Use a good style to write your code. Reading code written by others is usually not an enjoyable task. Reading horribly formatted code written by others is even worse. Your goal is to make your interviewer understand your code so that they can quickly evaluate if your code does what it is suppose to and if it solves a given problem.


Always explain to the interviewer what you are writing or typing. This is not about reading, verbatim, to the interviewer the code you are producing. Talk about the section of the code you are currently implementing at a higher level. Explain why it is written as such, and what it is trying to achieve.


When you copy and paste in code, consider whether it is necessary. Sometimes it is, sometimes it is not. If you find yourself copying and pasting a large chunk of code spanning multiple lines, it is probably an indicator that you can restructure the code by extracting those lines into a function. If it is just a single line you copied, usually it is fine.


After you have finished coding, do not immediately announce to the interviewer that you are done. In most cases, your code is usually not perfect. It may contain bugs or syntax errors. What you need to do is review your code.


Interviewers like it when you read their minds. What they usually do after you have finished coding is get you to write tests. It is a huge plus if you write tests for your code even before they prompt you to do so. You should be emulating a debugger when stepping through your code. Jot down or tell them the values of certain variables as you walk the interviewer through the lines of code.


If there are large duplicated chunks of code in your solution, restructure the code to show the interviewer that you value quality coding. Also, look out for places where you can do short-circuit evaluation.


Lastly, give the time and space complexities of your code, and explain why it is such. You can annotate chunks of your code with their various time and space complexities to demonstrate your understanding of the code. You can even provide the APIs of your chosen programming language. Explain any trade-offs in your current approach versus alternative approaches, possibly in terms of time and space.


Always validate input first. Check for inputs that are invalid, empty, negative, or different. Never assume you are given the valid parameters. Alternatively, clarify with the interviewer whether you can assume valid input (usually yes), which can save you time from writing code that does input validation.


If you are cutting corners in your code, state that out loud to your interviewer, and explain to them what you would do outside of an interview setting (no time constraints). For example, explain that you would write a regex to parse a string rather than using split , which does not cover all cases. 041b061a72


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