build: publish to Maven Central on version tags

.github/workflows/release.yml

@@ -0,0 +1,46 @@
+name: release
+
+# Publishes the library to Maven Central (Sonatype Central Portal) when a version tag is pushed,
+# then creates the matching GitHub Release. Credentials and the signing key are read from repo
+# secrets at publish time only -- see RELEASING.md for the one-time setup and how to cut a release.
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+permissions:
+  contents: write
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out source
+        uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+
+      - name: Set up Gradle
+        uses: gradle/actions/setup-gradle@v4
+
+      - name: Derive release version from tag
+        id: version
+        run: echo "version=${GITHUB_REF_NAME#v}" >> "$GITHUB_OUTPUT"
+
+      - name: Publish to Maven Central
+        env:
+          ORG_GRADLE_PROJECT_mavenCentralUsername: ${{ secrets.MAVEN_CENTRAL_USERNAME }}
+          ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.MAVEN_CENTRAL_PASSWORD }}
+          ORG_GRADLE_PROJECT_signingInMemoryKey: ${{ secrets.SIGNING_KEY }}
+          ORG_GRADLE_PROJECT_signingInMemoryKeyPassword: ${{ secrets.SIGNING_KEY_PASSWORD }}
+        run: ./gradlew publishToMavenCentral -PreleaseVersion=${{ steps.version.outputs.version }} --no-daemon --no-configuration-cache
+
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          generate_release_notes: true

RELEASING.md

@@ -0,0 +1,69 @@
+# Releasing JavaSake
+
+JavaSake is published to **Maven Central** (via the Sonatype Central Portal) so downstream projects
+can depend on it directly:
+
+```kotlin
+dependencies {
+    implementation("org.openminimed:javasake:<version>")
+}
+```
+
+Publishing is automated: pushing a `vX.Y.Z` tag builds, signs, and publishes the release, then
+creates a GitHub Release (`.github/workflows/release.yml`). Local builds and PRs always use a
+`-SNAPSHOT` version and never publish.
+
+## One-time setup (repo admin)
+
+Publishing requires four repository secrets. None are needed to build or test; they are read only by
+the `release` workflow.
+
+### 1. Maven Central namespace
+
+The published coordinate uses the `org.openminimed` group, so the Central Portal namespace
+`org.openminimed` must be verified once. Two options:
+
+- **`org.openminimed`** (current group) — requires verifying ownership of the `openminimed.org`
+  domain via a DNS TXT record in the Central Portal. Preferred if the org owns that domain.
+- **`io.github.openminimed`** — verified automatically against the GitHub org, no domain needed.
+  If you prefer this, change `group` in `lib/build.gradle.kts` accordingly before the first release.
+
+### 2. Central Portal user token
+
+In the Central Portal (https://central.sonatype.com) → *Account* → *Generate User Token*. Store the
+two halves as:
+
+- `MAVEN_CENTRAL_USERNAME`
+- `MAVEN_CENTRAL_PASSWORD`
+
+### 3. GPG signing key
+
+Central requires signed artifacts. Generate a key, publish its public half to a keyserver, then
+export the private key in-memory (ASCII-armored):
+
+```bash
+gpg --armor --export-secret-keys <KEY_ID>
+```
+
+Store as:
+
+- `SIGNING_KEY` — the full ASCII-armored private key block
+- `SIGNING_KEY_PASSWORD` — its passphrase
+
+Add all four under *Settings → Secrets and variables → Actions*.
+
+## Cutting a release
+
+1. Decide the version (SemVer, e.g. `0.2.0`).
+2. Tag and push:
+
+   ```bash
+   git tag v0.2.0
+   git push origin v0.2.0
+   ```
+
+3. The `release` workflow publishes to Central (auto-released once validation passes) and opens a
+   GitHub Release. The artifact typically appears on Central within ~15-30 minutes.
+
+Do **not** set the version in `lib/build.gradle.kts`; it is derived from the tag
+(`-PreleaseVersion`), so the tag is the single source of truth.

gradle/libs.versions.toml

@@ -4,6 +4,7 @@ junitPlatform = "1.11.3"
 bouncycastle = "1.79"
 spotless = "6.25.0"
 googleJavaFormat = "1.22.0"
+mavenPublish = "0.30.0"
 
 [libraries]
 junit-jupiter-api = { group = "org.junit.jupiter", name = "junit-jupiter-api", version.ref = "junit" }
@@ -13,3 +14,4 @@ bouncycastle = { group = "org.bouncycastle", name = "bcprov-jdk18on", version.re
 
 [plugins]
 spotless = { id = "com.diffplug.spotless", version.ref = "spotless" }
+mavenPublish = { id = "com.vanniktech.maven.publish", version.ref = "mavenPublish" }

lib/build.gradle.kts

@@ -1,15 +1,22 @@
+import com.vanniktech.maven.publish.JavaLibrary
+import com.vanniktech.maven.publish.JavadocJar
+import com.vanniktech.maven.publish.SonatypeHost
+
 plugins {
     `java-library`
     alias(libs.plugins.spotless)
+    alias(libs.plugins.mavenPublish)
 }
 
 group = "org.openminimed"
-version = "0.1.0-SNAPSHOT"
+
+// Release version is supplied by CI from the git tag (-PreleaseVersion=x.y.z); local builds and
+// PRs fall back to a -SNAPSHOT so nothing is ever accidentally published with a release version.
+version = (findProperty("releaseVersion") as String?) ?: "0.1.0-SNAPSHOT"
 
 java {
     sourceCompatibility = JavaVersion.VERSION_11
     targetCompatibility = JavaVersion.VERSION_11
-    withSourcesJar()
 }
 
 repositories {
@@ -40,3 +47,47 @@ spotless {
         endWithNewline()
     }
 }
+
+// Publishing to Maven Central via the Sonatype Central Portal. Credentials and the signing key are
+// injected from CI secrets at publish time only (see RELEASING.md); build and test need neither.
+mavenPublishing {
+    configure(JavaLibrary(javadocJar = JavadocJar.Javadoc(), sourcesJar = true))
+    publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL, automaticRelease = true)
+    signAllPublications()
+
+    coordinates(group.toString(), "javasake", version.toString())
+
+    pom {
+        name.set("JavaSake")
+        description.set(
+            "SAKE handshake and sequenced AES-CTR/CMAC session cipher for the JVM and Android.",
+        )
+        url.set("https://github.com/OpenMinimed/JavaSake")
+        inceptionYear.set("2026")
+
+        licenses {
+            license {
+                name.set("GNU General Public License v3.0")
+                url.set("https://www.gnu.org/licenses/gpl-3.0.txt")
+                distribution.set("repo")
+            }
+        }
+        developers {
+            developer {
+                id.set("palmarci")
+                name.set("Pal Marci")
+                url.set("https://github.com/palmarci")
+            }
+            developer {
+                id.set("openminimed")
+                name.set("OpenMinimed contributors")
+                url.set("https://github.com/OpenMinimed")
+            }
+        }
+        scm {
+            url.set("https://github.com/OpenMinimed/JavaSake")
+            connection.set("scm:git:https://github.com/OpenMinimed/JavaSake.git")
+            developerConnection.set("scm:git:ssh://git@github.com/OpenMinimed/JavaSake.git")
+        }
+    }
+}