How to secure a file by password

[miraks]

Hi,

I am writing an application which must be to open a file protected by a user password.

What is the best solution to secure a file by password ?

I imagine to copy the secured file (encrypted) into a temporary file not secured and open it. But how to do ?

Thank you in advance.

[wysota]

If you intend to copy the contents of a file to an unencrypted file, then don't encrypt it at all :)

I suggest you use some cryptographic streaming algorithm. I have once implemented a RC4 cipher as a QIODevice but you may use some ready made solutions (such as libcrypt from OpenSSL) that will decipher contents of a file into memory where you can access it, read it and wipe it out from memory when you don't need it anymore.

[rleojoseph]

what class file can be used to encyrpt a file ????????

[miraks]

I am using QCA.

[rleojoseph]

Hi, i am creating a texteditor using QT. I was trying to set a password for a file. What mechanism or class should i use to set a password for a file ??

Can you give me a minimal example that how i can make use of it in my project ??

Added after 55 minutes:

What is the QFile::EncoderFn and QFile::DecoderFn used for ??

[squidge]

Depends on your specification - do you want to add a password to a file, or encrypt a file to protect the file being opened without the password ?

[rleojoseph]

Ya. I want to add password for a file so that it will be opened if the password is correct.

[squidge]

As stated before the threads were merged, use the Qt Cryptographic Architecture.

How to use QCA depends on your specifications - the first thing you need is a cipher, and then you need to decide how to encrypt/decrypt the data using your password.

[miraks]

You can find an example here: http://quickgit.kde.org/?p=skrooge.git&a=blob_plain&h=5f853d111898d1774072d4e06604d64f0e6291c8&f=skgbasemodeler/skgservices.cpp, in function SKGServices::cryptFile.