sha256 - calculate SHA-256 message digest

Purpose of the program

The sha256 program calculates and prints SHA-256 (256bit) checksums of all files that are passed to it as command line parameters. It can also be used to calculate SHA-1 (160bit), SHA-224 (224bit), SHA-384 (384bit) and SHA-512 (512bit) checksums, if desired.

Program call

Since this (obviously) is a command line program, you can call it via command line/ shell. A list of valid options follows below.

Synopsis

  sha256 [--sha1 | --sha224 | --sha256 | --sha384 | --sha512] FILENAME ...

Options + parameters

  --sha1
      Calculate SHA-1 (160 bit) checksums instead of SHA-256.

  --sha224
      Calculate SHA-224 (224 bit) checksums instead of SHA-256.

  --sha256
      Calculate SHA-256 (256 bit) checksums. This is the default.

  --sha384
      Calculate SHA-384 (384 bit) checksums instead of SHA-256.

  --sha512
      Calculate SHA-512 (512 bit) checksums instead of SHA-256.

  --help
      Show a help message and list valid program options.

  --version
      Print version information and quit.

  FILENAME
        path to a file that should be hashed. Can be repeated
        multiple times.

A typical call could look like:

sha256 foo.txt some_dir/bar.baz

This would calculate the SHA-256 message digests of foo.txt and bar.baz in the subdirectory some_dir. If one of the given files does not exist, the program quits.

Building from source

Prerequisites

To build sha256 from source you need a C++ compiler with support for C++11 and CMake 3.8 or later. It also helps to have Git, a distributed version control system, on your build system to get the latest source code directly from the Git repository.

All three can usually be installed by typing

apt-get install cmake g++ git

or

yum install cmake gcc-c++ git

into a root terminal.

Getting the source code

Get the source directly from Git by cloning the Git repository and change to the directory after the repository is completely cloned:

git clone https://gitlab.com/striezel/secure-hash-algorithm.git ./sha256
cd sha256
git submodule update --init --recursive

The last of the lines above initializes and updates the submodule that the sha256 source code needs, too, to be build from source.

Build process

The build process is relatively easy, because CMake does all the preparations. Starting in the root directory of the source, you can do the following steps:

mkdir build
cd build
cmake ../
make sha256 -j2

Now the sha256 binary is built and ready for use.

License, disclaimer and source code

Copyright 2015 Dirk Stolle

The program sha256 is released under the GNU General Public License version 3, a free software license. For the full text of the license consult the file LICENSE or view it online at http://www.gnu.org/licenses/gpl-3.0.html

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHAN- TABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

The program's source code is published at GitLab.com, the project itself is located at https://gitlab.com/striezel/secure-hash-algorithm