Question

Hi,

(C programming)

I am looking to write a program that will encrypt a text file automatically once program has opened, and have the option to decrypt it in a menu in my program.

I have multiple text files that I need to encrypt, and would like if the program could encrypt all of them at once.

I would also only like to decrypt the a text file once the name has been entered into a scanf function.

Answer 1

Encrypt/Decrypt Files in Linux using Ccrypt

Ccrypt is a command line tool for encryption and decryption of data. Ccrypt is based on the Rijndael cipher, the same cipher used in the AES standard. On the other hand, in the AES standard, a 128-bit block size is used, whereas ccrypt uses a 256-bit block size. Ccrypt commonly uses the .cpt file extension for encrypted files.

• It is a lightweight tool, the installation and use of this tool is pretty easy.
• It is designed to overcome the shortcomings of standard unix crypt utility.

Installation

sudo apt-get install ccrypt // in ubuntu

Ccript

• -e, –encrypt :Encrypt. This is the default mode. If filename arguments are given, encrypt the files and append the suffix .cpt to their names. Otherwise, run as a filter.
• -d, –decrypt: Decrypt. If filename arguments are given, decrypt the files and strip the suffix .cpt from the filenames, if present. Otherwise, run as a filter.
• -c, –cat: Decrypt one or more files to standard output. If no filename arguments are given, decrypt as a filter. Implies -l.
• -x, –keychange: Change the key of encrypted data. In this mode, ccrypt prompts for two passwords: the old one and the new one. If filename arguments are given, modify the files. Otherwise, run as a filter.
• -u, –unixcrypt: Simulate the old unix crypt command. Note: the cipher used by unix crypt has been broken and is not secure. Please use this option only to decrypt existing files. If filename arguments are given, decrypt the files to stdout. Otherwise, run as a filter. Note that for the unix crypt format, there is no easy way to detect whether a given key matches or not; thus, for safety, this mode does not overwrite files.

Encrypting files with Ccrypt

In order to encrypt file using this tool, use following syntax:

ccrypt filename

To encrypt a file : impfile

ccrypt impfile

Decrypt file with Ccrypt

Now in order to decrypt an already encrypted file, command syntax is:

ccrypt –d encryptedfilename