feat: Add the signer interface

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.2.1] - 2026-07-28
+
+### Added
+
+- Added the signer interface
+
 ## [1.2.0] - 2026-06-01
 
 ### Changed

pom.xml

@@ -20,7 +20,7 @@
   <name>Coinbase Java Core</name>
   <description>Core Java Libraries for Sample Applications</description>
   <groupId>com.coinbase.core</groupId>
-  <version>1.2.0</version>
+  <version>1.2.1</version>
   <url>https://github.com/coinbase/core-java</url>
   <licenses>
     <license>

src/main/java/com/coinbase/core/credentials/Signer.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2026-present Coinbase Global, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.coinbase.core.credentials;
+
+import com.coinbase.core.errors.CoinbaseClientException;
+
+public interface Signer {
+  byte[] sign(byte[] message) throws CoinbaseClientException;
+}