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I am making a program in Qt5.2.1 and in it I am using a text file to store some data. I would like to encrypt it and decrypt it inside the program and display the text stored in the file in a QPlainTextEdit ( or any other similar widget).
I searched and came across Qcryptographichash but i have no idea how to use it. I read somewhere that it does not provide a very secure encryption but that doesn't matter ( I am not expecting hackers to try and read this file).
So, could anyone guide me in the right direction, maybe even give me some code. :D
QCryptographic hash creates a hash from given data. That is a one-way process, so the it will not do what you want, namely encrypt the data in a form that can be retrieved via decryption.
You can read more about the difference between encryption and hashes here.
You need to research into possible encryption algorithms. To my knowledge, that's not something that is part of Qt.
It's a large area of on-going research; there are so many to choose from, as you can see here.
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I'm building a program that I want to be able to exchange information with other programs running in another computer. I started using C# and a library called SimpleTCP. The main issue is that is too simple and only send and receive messages.
I'm looking for something that I can predetermine functions that one or the other can call from each other.
I looked on google and stack overflow but I was unable to find an appropriated subject to study, what should I be looking for to learn this? Thank you
The most complete protocol for what you want is gRPC. There is a learning curve but worth it in my opinion. https://github.com/grpc/grpc
There is a way but it's little bit different
Such programs like this written in tow different languages
You can make a center database between the both programs
In this situation it's very easy to communicate and receive ,send data
You can mysql ,oracl, mariadb or any Database you prefer
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I'm writing relatively small, but not simple networking library which is going to be used at least from C,java,python,ruby and C#. Is there a way to make go bindings to the other languages the way in can be done form C? If not is there other way?
Right now, you can't write libraries in Go that can be used in other languages. Go has a runtime environment that does a lot of things (like sheduling go-routines, collecting garbage) for you. This runtime environment is written under the assumption that it controls the whole program. This assumption does not hold if Go code would be used from inside another language, as the Go library cannot influence the binary that uses it.
I imagine that a JSON service would do what you describe.
Have a look at the json test for a simple example
It wouldnt matter what languages you used to set and get data from your app
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This question is partly theoretical and partly practical. A perfect answer would answer theoretically why, and practically how.
Question
Given an encrypted file, and a non-encrypted version of the same file, can the encryption key be recovered? More specifically how might one achieve this?
Background
I have some backup files from a colleagues old machine. They have been stored in an encrypted 7zip file. The file table has not been encrypted, so it should be possible to isolate individual files. What I don't have is the actual encryption key (due to a storage medium failure). I do however have some unencrypted files which are also in the container. How can I use these to recover the whole archive?
As others have said, this is a "Known Plaintext Attack". All good cyphers are proof against such an attack. Any cypher which cannot withstand such an attack never gets off the starting blocks.
The best suggestion is to find out the specific encryption method used and look for specific weaknesses in that particular method. Alternatively, ask people who knew the key if they can remember even part of the original password. "It began with a D" will reduce the work you need to do to brute force it by a factor of 26 or 52.
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My software is a video-audio converter and video cutter. I have used Qt(compiled from source) and ffmpeg (compiled from source). I have to prepare System Usage Specification outline and Specify Usage patterns of the system and indicate it using Run charts / Histograms. I am told to use Winrunner for this purpose. I don't know exactly what to do. Please help.
I never heard about 'System Usage Specification', this must be a terminology specific to your company.
A wild guess would be that it's something close to the Use Case diagram of UML, to define what the users can do and which action they have to perform to lead them to the expected result.
Sounds like a uggly word for "handbook" or "usage guide" from the pov of a end-user (though I never heared of that specific term)
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Let say that I have a website with some information that could be access externally. Those information need to be only change by the respected client. Example: Google Analytic or WordPress API key. How can I create a system that work like that (no matter the programming language)?
A number of smart people are working on a standard, and it's called OAuth. It already has a number of sample implementations, so it's pretty easy to get started.
Simple:
Generate a key for each user
Deny access for each request without this key
Currently, I use a concatenation of multiple MD5s with a salt. The MD5s are generated off of various concatenations of user data.
A good way of generating a key would be to store a GUID (Globally Unique Identifier) on each user record n the database. GUID is going to be unique and almost impossible to guess.
There are also infrastructure services that manage all this for you like http://www.3scale.net (disclosure I work there), http://www.mashery.com and http://www.apigee.com/.