Add message signing digest generator

concordium-sdk/src/main/java/com/concordium/sdk/transactions/MessageSigningDigest.java

@@ -0,0 +1,47 @@
+package com.concordium.sdk.transactions;
+
+import com.concordium.sdk.crypto.SHA256;
+import com.concordium.sdk.types.AccountAddress;
+import com.concordium.sdk.types.UInt64;
+import lombok.SneakyThrows;
+import lombok.val;
+
+import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
+
+public class MessageSigningDigest {
+
+    /**
+     * Creates a digest for signing a regular message with {@link TransactionSigner}.
+     *
+     * @param address address of the account signing the message.
+     * @param message message contents.
+     * @return 32-byte digest which can be signed by {@link TransactionSigner}.
+     */
+    public static byte[] from(AccountAddress address, byte[] message) {
+        // When signing a transaction, the 32 bytes of the account address
+        // gets followed by the account nonce, which is uint64 and by design >= 1.
+        // In order to sign a regular message and ensure that the user
+        // does not accidentally sign a transaction, 0 is used as certainly invalid nonce.
+        // This results in the following sequence: [32 bytes of the address, 8 zero bytes, message].
+        val finalMessage = ByteBuffer
+                .allocate(AccountAddress.BYTES + UInt64.BYTES + message.length)
+                .put(address.getBytes())
+                .put(new UInt64(0).getBytes())
+                .put(message)
+                .array();
+        return SHA256.hash(finalMessage);
+    }
+
+    /**
+     * Creates a digest for signing a regular plain-text message with {@link TransactionSigner}.
+     *
+     * @param address address of the account signing the message.
+     * @param message plain-text message.
+     * @return 32-byte digest which can be signed by {@link TransactionSigner}.
+     */
+    @SneakyThrows
+    public static byte[] from(AccountAddress address, String message) {
+        return from(address, message.getBytes(StandardCharsets.UTF_8));
+    }
+}

concordium-sdk/src/test/java/com/concordium/sdk/transactions/MessageSigningDigestTest.java

@@ -0,0 +1,76 @@
+package com.concordium.sdk.transactions;
+
+import com.concordium.sdk.types.AccountAddress;
+import lombok.SneakyThrows;
+import lombok.val;
+import org.apache.commons.codec.binary.Hex;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertArrayEquals;
+
+public class MessageSigningDigestTest {
+    private static final AccountAddress SIGNER_ADDRESS =
+            AccountAddress.from("3WZE6etUvVp1eyhEtTxqZrQaanTAZnZCHEmZmDyCbCwxnmQuPE"); //  Dummy address
+
+    private final Map<String, String> hexTestVectors = new HashMap<>();
+    private final Map<String, String> plainTestVectors = new HashMap<>();
+
+    @Before
+    @SneakyThrows
+    public void setup() {
+        hexTestVectors.put(
+                "01000000010000000000000000000000000000000000000000000000000000000000000000ffffffff4d04ffff001d0104455468652054696d65732030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73ffffffff0100f2052a01000000434104678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5fac00000000",
+                "e8a1287efd3a0d41e4b7b0a7951c5b67421bd87e659408494c8174c5bef3df09"
+        );
+        hexTestVectors.put(
+                "d090d0b1d180d0b0d0bad0b0d0b4d0b0d0b1d180d0b0",
+                "f31c19fa2087a2f04f3cbb91cad10c4081969f29e8407930ce13f50682d9c470"
+        );
+        hexTestVectors.put(
+                "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",
+                "38b12945d2f06d444b177ba4e4f1038f070646bfd313adbe5b8e1401ece2702c"
+        );
+        hexTestVectors.put(
+                "",
+                "c425a3ee7a5706ae8e09884693bd2ba80e843bc7983bac559a3f9edb545acf0c"
+        );
+
+        plainTestVectors.put(
+                "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks",
+                "6d054bda20eb34b96d7e2e43df2238f33d50982d183e2589a520762b1a766f90"
+        );
+        plainTestVectors.put(
+                "Абракадабра",
+                "f31c19fa2087a2f04f3cbb91cad10c4081969f29e8407930ce13f50682d9c470"
+        );
+        plainTestVectors.put(
+                "",
+                "c425a3ee7a5706ae8e09884693bd2ba80e843bc7983bac559a3f9edb545acf0c"
+        );
+    }
+
+    @SneakyThrows
+    @Test
+    public void testDigestHex() {
+        for (String messageHex : hexTestVectors.keySet()) {
+            val message = Hex.decodeHex(messageHex);
+            val expected = Hex.decodeHex(hexTestVectors.get(messageHex));
+            val actual = MessageSigningDigest.from(SIGNER_ADDRESS, message);
+            assertArrayEquals(expected,actual);
+        }
+    }
+
+    @SneakyThrows
+    @Test
+    public void testDigestPlain() {
+        for (String message : plainTestVectors.keySet()) {
+            val expected = Hex.decodeHex(plainTestVectors.get(message));
+            val actual = MessageSigningDigest.from(SIGNER_ADDRESS, message);
+            assertArrayEquals(expected,actual);
+        }
+    }
+}