Make your published artifacts bit-by-bit reproducible, and verify against other certifications
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sbt plugin to make sbt builds more reproducible.

For general information on 'Reproducible Builds', see

This plugin provides a number of features:

  • Strip 'accidental' sources of nondeterminism (e.g. timestamps) from the packaged jar
  • Produce a (signed) 'buildinfo' file describing the build environment used and containing a cryptographic hash of the resulting artifacts.
  • Upload this certification to a reproducible-builds-certification-repository instance
  • Check your local build against already-uploaded certifications


Stripping nondeterminism from artifacts

Then add to your project/plugins.sbt:

addSbtPlugin("net.bzzt" % "sbt-reproducible-builds" % "0.15")

And to build.sbt:


The built artifact can be found under target/scala-${scalaBinaryVersion}/stripped/${reproducibleBuildsPackageName}-${version}.jar.

Interoperability with other sbt plugins


As this plugin as well as the sbt-osgi plugin redefine the packageBin task, it is necessary to re-apply the plugin settings after the application of the osgi settings. You can find an example under src/sbt-test/sbt-reproducible-builds/osgi/build.sbt.

Describe your build as a 'buildinfo' certification

You can now generate a signed description of the build environment with the sbt task signedReproducibleBuildsCertification.

Sharing certifications

Upload your certification to a reproducible-builds-certification-repository instance with reproducibleBuildsUploadCertification.

Uploading certifications from Travis

Especially if you're already deploying from Travis, it can be a great start to publish certifications from Travis as well. For this, you should give Travis its own gpg key pair to sign those certifications.

Start by generating a keypair with gpg --gen-key, naming it something like "Arnout Engelen (via Travis)". Then export public and private key with gpg --export -a "Arnout Engelen (via Travis)" > public.key and gpg --export-secret-key -a "Arnout Engelen (via Travis)" > private.key. Now encrypt the private key so only Travis can read it with travis encrypt-file .travis/private.key and follow the instructions to unencrypt. Finally, gpg --import private.key public.key and sbt reproducibleBuildsUploadCertification to sign and upload the certification from Travis.

Checking certifications

Check your certification with other uploaded certifications with reproducibleBuildsCheckCertification

Drinking our own champagne

From version 0.3 onwards, sbt-reproducible-builds should itself be reproducible in the sense that building the same git tag should produce the exact same binary.

When this is not the case, this is to be considered a bug and a bug report with the binary, the buildinfo and any additional information about any peculiarities of the build system would be greatly appreciated!