dotsig: digital signatures on-the-fly

The dotsig software lets you create and verify digital signatures using RSA cryptography (PKCS1 v1.5), PGP and elliptic-curve cryptography (ECDSA).

You can find the reference documentation here.

This software is released under the 3-Clause BSD License.

Releases

The dotsig software is currently under active development and frequent changes to the source code are to be expected until the software reaches a stable tag.

The latest release as of May 13th 2024 is: v1.1.0-RC.1.

Use dotsig -v to find out the version installed on your system.

Getting started

Using the pre-built executable

Download the latest version of dotsig here for your system and install it. Then run one of the commands below to check that your installation works:

dotsig -v
dotsig -h
echo 'Hello, world!' | dotsig

Cross-platform Identities

Identities' private keys are tentatively exported to encrypted DER-encoded files in the home folder of the user running the program, whereas identities' public keys are tentatively exported to plaintext PEM-encoded files ending with .pub.

For Windows users, the APPDATA environment variable is used and the files are stored in %APPDATA%\.dotsig\, whereas on Unix systems (including Mac OS), the identity files are stored in ~/.dotsig.

✅ Note that it is possible to re-use your RSA identity file (e.g. -i ~/.ssh/id_rsa) provided that you are in possession of the passphrase that unlocks the private key.

Developers notes

Install required dependencies

Following dependencies must be installed on the host system if you want to build the dotsig software from its source code:

• g++-11 or newer (must have support for -std=c++-20)
• Python v3.6.10 (python3 -V)
• Botan v3.4.0

You will need to install the Botan library on your host computer. You can do this manually using the instructions provided in the Botan build instructions. The source code repository for Botan can be found on Github.

Note that the current CMakeLists.txt statically links the libstdc++ package and it may be that cmake can't find it due to the restrictive HINTS added in the build instructions.

Build the source code

A CMakeLists.txt file is provided to overcome the necessity of building the package. This is currently the preferred method to build the dotsig software.

cd build
cmake ..
cmake --build .
cmake --build . --target install -- DESTDIR=stage
cd stage/usr/local/bin

🔜 In the short-to-mid-term future, I plan to enable the installations using popular package managers including: apt, rpm and snap.

Build using Windows

If you are using a Windows operating system, you will need a couple of special configuration commands after having built the Botan library locally. To start configuring a Windows build, use:

cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -G "NMake Makefiles"
nmake
cmake --build . --target install -- DESTDIR=stage
cd "stage/Program Files (x86)/dotsig/bin"

Creating installer packages

The cpack utility can be used to create installer packages for different OSs. It is more comfortable for the end-user to receive an installer package rather than being able to download only the binaries, for Windows it is also necessary because of the botan-3.dll file that is needed to run the software.

To create an installer package after having built your source tree with one of the above commands, and using the corresponding operating system, use:

# MacOS .sh, .tar.gz, .pkg
cpack -G "STGZ"
cpack -G "TGZ"
cpack -G "productbuild"

# Linux .tar.gz, .deb, .rpm
cpack -G "TGZ"
cpack -G "DEB"
cpack -G "RPM"

# Windows .zip
cpack -G "ZIP"

Installing the user manual

A man user manual is available with docs/dotsig.1, you can install it on your system using the make install-man command from the root project folder.

You can also directly use this file to open it with man: man docs/dotsig.1.

Examples

By default, this software uses the ECDSA standard to sign/verify documents. You can change the algorithm used between ecdsa and pkcs using e.g.: -a pkcs.

To sign/verify a file with ECDSA and your default identity ~/id_ecdsa, use:

dotsig path/to/document
dotsig -c path/to/document.sig

To sign/verify a file with PKCS and your default identity ~/id_rsa, use:

dotsig path/to/document -a pkcs
dotsig -c path/to/document.sig -a pkcs

To sign/verify a message with ECDSA and your default identity, use:

echo 'Hello, World!' | dotsig
echo 'Hello, World!' | dotsig -c path/to/signature.sig

To sign/verify a message with PKCS and your default identity, use:

echo 'Hello, World!' | dotsig -a pkcs
echo 'Hello, World!' | dotsig -c path/to/signature.sig -a pkcs

Example of a full-cycle of creation of a digital signature and later verification of the produced signature file (using STDIN):

echo 'Hello, World!' | dotsig
echo 'Hello, World!' | dotsig -c stdin.sig

Getting help

Use the following available resources to get help:

• Find the github repository: evias/dotsig.
• Read the reference documentation.
• Read the manpage: man dotsig.
• Read the usage message: dotsig -h.
• Find out about changes in the changelog.
• If you found a bug, make sure to open a new issue.

License

Copyright 2024 Grégory Saive [email protected] for re:Software S.L. (resoftware.es).

Licensed under the 3-Clause BSD License.