Signify: Cryptographically Sign and Verify Files

Introduction

Written in 2014 for OpenBSD, signify is a tool to cryptographically sign and verify files:

It only supports a single algorithm, Ed25519, created by djb and his gang. It’s fast, immune to timing attacks by design, produce deterministic signatures, uses small keys and produce small signatures, … it does look like a sound choice.

Signify's main benefits is that it has a small codebase and is not based on GnuPG. On the downside, there is no revocation mechanism and the trust path relies on getting the key directly from a trusted developer.

Signify's usage is not just limited to OpenBSD and the tool has also been been packaged in Debian. To learn more about signify, refer to this blog post ^[archive] by the original author.

Installation and Usage

In the steps below, installing package qrencode is optional and only needed if you intend to create QR codes.

1. Install signify.

Install signify-openbsd qrencode.

1. Update the package lists.

sudo apt-get update

sudo apt-get update

2. Upgrade the system.

sudo apt-get dist-upgrade

sudo apt-get dist-upgrade

3. Install the signify-openbsd qrencode package.

Using apt-get command line parameter --no-install-recommends is in most cases optional.

sudo apt-get install --no-install-recommends signify-openbsd qrencode

sudo apt-get install --no-install-recommends signify-openbsd qrencode

The procedure of installing signify-openbsd qrencode is complete.

2. Create a key.

This only needs to be done once unless multiple keys are desired; in that case different key names should be used. In the following example, keyname is used as the sample key name.

signify-openbsd -G -p keyname.pub -s keyname.sec

signify-openbsd -G -p keyname.pub -s keyname.sec

3. Optional: Add a key comment.

Replace comments here with the actual comment but keep the ". The comment could be a name, position, website, e-mail address and/or anything else.

signify-openbsd -G -p keyname.pub -s keyname.sec -c "comments here"

signify-openbsd -G -p keyname.pub -s keyname.sec -c "comments here"

Note:

• The private key file keyname.sec needs to stay private -- never share keyname.sec with anyone as this would defeat the purpose of signing files!
• The public key file keyname.pub can be shared with anyone.

4. Utilize signify.

To sign a file message.txt (which has to be created by the user beforehand).

signify-openbsd -S -s keyname.sec -m message.txt

signify-openbsd -S -s keyname.sec -m message.txt

This will create a signature file message.txt.sig.

To verify a file message.txt with signature file message.txt.sig.

signify-openbsd -V -p keyname.pub -m message.txt

signify-openbsd -V -p keyname.pub -m message.txt

5. Optional: Create a QR code for the public key.

qrencode -r keyname.pub -o keyname.pub.png

qrencode -r keyname.pub -o keyname.pub.png

File keyname.pub.png would be the QR code of the public key.

Refer to the Debian signify-openbsd Manual Page ^[archive] for further options.

See Also

• Verify the Whonix ™ Signify Signatures

Footnotes

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