WIP

README.md

@@ -30,7 +30,7 @@ does not have floats, and they do not exist at all in the Sophia language.
 
 ## Terms
 
-Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
 Project: Gajumaru Core Java Libraries
 
 This program is dual-licensed:
@@ -38,10 +38,10 @@ This program is dual-licensed:
    Software Foundation, either version 3 of the License, or (at your option) 
    any later version (AGPL-3.0-or-later). (See LICENSE file.)
 
-2) Under a commercial/proprietary license available directly from QPQ AG.
+2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
    If you wish to use this software outside the strict constraints of the 
    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
-   purchase a commercial license from QPQ AG.
+   purchase a commercial license from QPQ IaaS AG.
 
 Authors:
   - Craig Everett <craigeverett@qpq.swiss>

bin/compile

@@ -1,6 +1,6 @@
 #! /usr/bin/env bash
 
-# Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+# Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
 # SPDX-License-Identifier: AGPL-3.0-or-later OR LicenseRef-QPQ-Commercial
 
 set -e

bin/run

@@ -1,6 +1,6 @@
 #! /usr/bin/env bash
 
-# Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+# Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
 # SPDX-License-Identifier: AGPL-3.0-or-later OR LicenseRef-QPQ-Commercial
 
 set -e

src/main/java/swiss/qpq/gajumaru/core/crypto/Blake2b.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>
@@ -21,7 +21,6 @@
 package swiss.qpq.gajumaru.core.crypto;
 
 import java.util.Arrays;
-import swiss.qpq.gajumaru.core.tools.CryptoUtils;
 
 
 // Pure Java implementation of BLAKE2b.

src/main/java/swiss/qpq/gajumaru/core/crypto/Ed25519.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option)
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>
@@ -228,6 +228,20 @@ public final class Ed25519 {
         return ok;
     }
 
+    /**
+     * Signs a message using a 64-byte secret key (seed | public_key).
+     * This matches the libsodium behavior.
+     */
+    public static byte[] signWithExpandedKey(byte[] message, byte[] sk64) {
+        byte[] seed = new byte[32];
+        System.arraycopy(sk64, 0, seed, 0, 32);
+        try {
+            return sign(seed, message);
+        } finally {
+            CryptoUtils.wipe(seed);
+        }
+    }
+
     // NOTE:
     // Internal curve and field arithmetic machinery.
     // These are public only for parity testing against reference implementations.

src/main/java/swiss/qpq/gajumaru/core/crypto/Keccak256.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>
@@ -29,7 +29,6 @@ import swiss.qpq.gajumaru.core.tools.CryptoUtils;
 
 public final class Keccak256 {
 
-    private static final int LANE_SIZE = 64;
     private static final int STATE_SIZE = 25;
     private static final int CAPACITY = 512;
     private static final int BITRATE = 1600 - CAPACITY; // 1088 bits = 136 bytes

src/main/java/swiss/qpq/gajumaru/core/crypto/Vault.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>
@@ -20,6 +20,7 @@
 
 package swiss.qpq.gajumaru.core.crypto;
 
+import java.security.SecureRandom;
 import javax.crypto.Cipher;
 import javax.crypto.SecretKey;
 import javax.crypto.spec.GCMParameterSpec;
@@ -32,54 +33,58 @@ public final class Vault {
 
     private static final String AES_GCM = "AES/GCM/NoPadding";
     private static final int GCM_TAG_LENGTH = 128; // Bits
+    private static final int IV_LENGTH = 12; // Bytes
 
     private Vault() {}
 
     /**
      * Holds the results of an encryption operation.
      */
-    public static final class Ciphertext {
-        private final byte[] iv;
-        private final byte[] data;
-
-        public Ciphertext(byte[] iv, byte[] data) {
-            this.iv = iv;
-            this.data = data;
-        }
-
-        public byte[] getIv() { return iv; }
-        public byte[] getData() { return data; }
-    }
+    public record Ciphertext(byte[] iv, byte[] data) {}
 
     /**
      * Encrypts plaintext using AES/GCM.
-     * Letting the provider generate the IV (required by Android Keystore).
+     * Manually generates the IV to ensure deterministic tag length and cross-provider consistency.
      */
     public static Ciphertext encrypt(SecretKey key, byte[] plaintext) throws Exception {
-        Cipher cipher = Cipher.getInstance(AES_GCM);
-        cipher.init(Cipher.ENCRYPT_MODE, key);
-        byte[] iv = cipher.getIV();
-        byte[] ciphertext = cipher.doFinal(plaintext);
-        return new Ciphertext(iv, ciphertext);
+        try {
+            byte[] iv = new byte[IV_LENGTH];
+            new SecureRandom().nextBytes(iv);
+            
+            byte[] ciphertext = encrypt(key, iv, plaintext);
+            return new Ciphertext(iv, ciphertext);
+        } catch (Exception e) {
+            throw new Exception("Vault.encrypt failed: " + e.getMessage(), e);
+        }
     }
 
     /**
      * Encrypts plaintext using AES/GCM with a specific IV.
      */
     public static byte[] encrypt(SecretKey key, byte[] iv, byte[] plaintext) throws Exception {
-        Cipher cipher = Cipher.getInstance(AES_GCM);
-        GCMParameterSpec spec = new GCMParameterSpec(GCM_TAG_LENGTH, iv);
-        cipher.init(Cipher.ENCRYPT_MODE, key, spec);
-        return cipher.doFinal(plaintext);
+        try {
+            Cipher cipher = Cipher.getInstance(AES_GCM);
+            GCMParameterSpec spec = new GCMParameterSpec(GCM_TAG_LENGTH, iv);
+            cipher.init(Cipher.ENCRYPT_MODE, key, spec);
+            return cipher.doFinal(plaintext);
+        } catch (Exception e) {
+            throw new Exception("Vault.encrypt(iv) failed: " + e.getClass().getName() + ": " + e.getMessage(), e);
+        }
     }
 
     /**
      * Decrypts ciphertext using AES/GCM.
      */
     public static byte[] decrypt(SecretKey key, byte[] iv, byte[] ciphertext) throws Exception {
-        Cipher cipher = Cipher.getInstance(AES_GCM);
-        GCMParameterSpec spec = new GCMParameterSpec(GCM_TAG_LENGTH, iv);
-        cipher.init(Cipher.DECRYPT_MODE, key, spec);
-        return cipher.doFinal(ciphertext);
+        try {
+            Cipher cipher = Cipher.getInstance(AES_GCM);
+            GCMParameterSpec spec = new GCMParameterSpec(GCM_TAG_LENGTH, iv);
+            cipher.init(Cipher.DECRYPT_MODE, key, spec);
+            return cipher.doFinal(ciphertext);
+        } catch (Exception e) {
+            String msg = e.getMessage();
+            if (msg == null) msg = e.toString();
+            throw new Exception("Vault.decrypt failed [" + e.getClass().getSimpleName() + "]: " + msg, e);
+        }
     }
 }

src/main/java/swiss/qpq/gajumaru/core/data/Id.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/data/SignedTx.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/data/SpendTx.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/encoding/ApiEncoder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/encoding/Base58.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/encoding/ChainObjects.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/encoding/Gf256.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option)
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/encoding/Mnemonic.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>
@@ -99,7 +99,7 @@ public final class Mnemonic {
         "broken", "bronze", "broom", "browse", "bruise", "brunt", "brute", "bubble", "buckle", "buddy", 
         "budget", "buffet", "builder", "bulb", "bulge", "bulimia", "bulky", "bulletin", "bummed", "bumpy", 
         "bundle", "bungalow", "bunion", "bunker", "buoyant", "burden", "bureau", "burger", "burial", 
-        "burlap", "burnout", "blurp", "burrito", "burst", "bushel", "business", "bustle", "busy", "butane", 
+        "burlap", "burnout", "burp", "burrito", "burst", "bushel", "business", "bustle", "busy", "butane", 
         "butcher", "butler", "button", "buxom", "buyer", "buyout", "buzz", "bylaw", "bypass", "cabaret", 
         "cabbage", "cabin", "cactus", "cadaver", "cadet", "caffeine", "caftan", "cage", "cairn", "cajole", 
         "calamity", "calcium", "calendar", "calico", "callous", "calm", "calorie", "calypso", "camera", 

src/main/java/swiss/qpq/gajumaru/core/encoding/QR.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option)
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/encoding/RLP.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/encoding/ZJ.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option)
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/formatting/GajuFormat.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/tools/CryptoUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option) 
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the 
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must 
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>

src/main/java/swiss/qpq/gajumaru/core/tools/Grids.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option)
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>
@@ -29,7 +29,7 @@ import java.util.Map;
 
 // GRIDS URL handling, ported from hz_grids.erl.
 
-public final class Grids {
+public final class  Grids {
 
     private Grids() {}
 
@@ -93,21 +93,23 @@ public final class Grids {
             if (path.startsWith("/1/s/")) {
                 String recipient = path.substring(5);
                 Map<String, String> qargs = parseQuery(query);
-                BigInteger amount = new BigInteger(qargs.getOrDefault("a", "0"));
+                String a = qargs.get("a");
+                BigInteger amount = (a == null || a.isEmpty()) ? BigInteger.ZERO : new BigInteger(a);
                 byte[] payload = decodePayload(qargs.getOrDefault("p", ""));
                 return ParseResult.spend(Context.CHAIN, host, recipient, amount, payload);
             } else if (path.startsWith("/1/t/")) {
                 String recipient = path.substring(5);
                 Map<String, String> qargs = parseQuery(query);
-                BigInteger amount = new BigInteger(qargs.getOrDefault("a", "0"));
+                String a = qargs.get("a");
+                BigInteger amount = (a == null || a.isEmpty()) ? BigInteger.ZERO : new BigInteger(a);
                 byte[] payload = decodePayload(qargs.getOrDefault("p", ""));
                 String location = host + (uri.getPort() != -1 ? ":" + uri.getPort() : "");
                 return ParseResult.transfer(Context.NODE, location, recipient, amount, payload);
             } else if (path.startsWith("/1/d/")) {
-                String subPath = path.substring(5);
+                String subPath = path.substring(4); // Includes the leading slash
                 String httpScheme = "grids".equals(scheme) ? "https" : "http";
-                String baseUrl = httpScheme + "://" + host + (uri.getPort() != -1 ? ":" + uri.getPort() : "") + subPath;
-                String httpUrl = query != null ? baseUrl + "?" + query : baseUrl;
+                String hostPart = host + (uri.getPort() != -1 ? ":" + uri.getPort() : "");
+                String httpUrl = httpScheme + "://" + hostPart + subPath + (query != null ? "?" + query : "");
                 return ParseResult.sign("grids".equals(scheme) ? Context.HTTPS : Context.HTTP, httpUrl);
             } else {
                 throw new IllegalArgumentException("Unknown verb in path: " + path);
@@ -118,8 +120,8 @@ public final class Grids {
     }
 
     public static final String REQ_TYPE_MESSAGE = "message";
+    public static final String REQ_TYPE_BINARY  = "binary";
     public static final String REQ_TYPE_TX      = "tx";
-    public static final String REQ_TYPE_ACK     = "ack";
 
     public static Map<String, Object> makeRequest(String type, Object payload, String publicId, String networkId) {
         Map<String, Object> req = new LinkedHashMap<>();

src/main/java/swiss/qpq/gajumaru/core/tools/Http.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
+ * Project: Gajumaru Core Java Libraries <gajumaru.io>
+ *
+ * This program is dual-licensed:
+ * 1) Under the GNU Affero General Public License as published by the Free
+ *    Software Foundation, either version 3 of the License, or (at your option)
+ *    any later version (AGPL-3.0-or-later).
+ *
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
+ *    If you wish to use this software outside the strict constraints of the
+ *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
+ *    purchase a commercial license from QPQ IaaS AG.
+ *
+ * Authors:
+ *   - Craig Everett <craigeverett@qpq.swiss>
+ *
+ * SPDX-License-Identifier: AGPL-3.0-or-later OR LicenseRef-QPQ-Commercial
+ */
+
+package swiss.qpq.gajumaru.core.tools;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+import swiss.qpq.gajumaru.core.encoding.ZJ;
+
+// Minimal HTTP client for GRIDS and Node interaction.
+
+public final class Http {
+
+    private Http() {}
+
+    public static Object get(String url) throws Exception {
+        return request(url, "GET", null);
+    }
+
+    public static Object post(String url, Object body) throws Exception {
+        return request(url, "POST", body);
+    }
+
+    private static Object request(String urlStr, String method, Object body) throws Exception {
+        URL url = new java.net.URI(urlStr).toURL();
+        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
+        conn.setRequestMethod(method);
+        conn.setConnectTimeout(15000);
+        conn.setReadTimeout(15000);
+        conn.setInstanceFollowRedirects(true);
+        
+        // Emulate a standard browser agent to avoid being blocked by strict servers
+        conn.setRequestProperty("Accept", "application/json, text/plain, */*");
+        conn.setRequestProperty("User-Agent", "Mozilla/5.0 (Linux; Android 10) GajuMobile/1.0");
+
+        if (body != null) {
+            conn.setRequestProperty("Content-Type", "application/json");
+            conn.setDoOutput(true);
+            try (OutputStream os = conn.getOutputStream()) {
+                byte[] input;
+                if (body instanceof String) {
+                    input = ((String) body).getBytes(StandardCharsets.UTF_8);
+                } else {
+                    input = ZJ.encode(body).getBytes(StandardCharsets.UTF_8);
+                }
+                os.write(input, 0, input.length);
+            }
+        }
+
+        int code = conn.getResponseCode();
+        
+        StringBuilder response = new StringBuilder();
+        try (java.io.InputStream is = (code >= 200 && code < 300) ? conn.getInputStream() : conn.getErrorStream();
+             BufferedReader br = new BufferedReader(new InputStreamReader(is, StandardCharsets.UTF_8))) {
+            String line;
+            while ((line = br.readLine()) != null) {
+                response.append(line).append("\n");
+            }
+        }
+
+        String responseStr = response.toString().trim();
+        
+        if (code < 200 || code >= 300) {
+            String reason = "HTTP " + code;
+            try {
+                Object decoded = ZJ.decode(responseStr);
+                if (decoded instanceof Map) {
+                    Object r = ((Map<?, ?>) decoded).get("reason");
+                    if (r != null) reason = r.toString();
+                }
+            } catch (Exception ignored) {}
+            throw new Exception(reason + " (URL: " + urlStr + ")");
+        }
+
+        if (responseStr.isEmpty()) return null;
+
+        try {
+            return ZJ.decode(responseStr);
+        } catch (Exception e) {
+            if (responseStr.startsWith("<")) {
+                throw new Exception("Server returned HTML instead of JSON (URL: " + urlStr + ")");
+            }
+            throw new Exception("JSON parse failed for " + urlStr + ": " + e.getMessage());
+        }
+    }
+}

src/main/java/swiss/qpq/gajumaru/core/tools/JavaSigningProvider.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
+ * Project: Gajumaru Core Java Libraries <gajumaru.io>
+ *
+ * This program is dual-licensed:
+ * 1) Under the GNU Affero General Public License as published by the Free
+ *    Software Foundation, either version 3 of the License, or (at your option)
+ *    any later version (AGPL-3.0-or-later).
+ *
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
+ *    If you wish to use this software outside the strict constraints of the
+ *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
+ *    purchase a commercial license from QPQ IaaS AG.
+ *
+ * Authors:
+ *   - Craig Everett <craigeverett@qpq.swiss>
+ *
+ * SPDX-License-Identifier: AGPL-3.0-or-later OR LicenseRef-QPQ-Commercial
+ */
+
+package swiss.qpq.gajumaru.core.tools;
+
+import swiss.qpq.gajumaru.core.crypto.Ed25519;
+
+/**
+ * JavaSigningProvider implements SigningProvider using pure Java Ed25519 arithmetic.
+ */
+public final class JavaSigningProvider implements SigningProvider {
+
+    @Override
+    public byte[] cryptoSignSeedKeypair(byte[] seed) {
+        byte[] pub = Ed25519.publicKey(seed);
+        // Pure Java Ed25519 needs a way to get the expanded secret key.
+        // In Ed25519.sign it's: hash = sha512(seed); s = hash[0..31]; s[0] &= 248; s[31] &= 127; s[31] |= 64;
+        // Prefix is hash[32..63].
+        // Libsodium's 64-byte SK is often [32-byte seed | 32-byte public key].
+        // However, Ed25519.sign implementation expects the 64-byte expanded key to work correctly.
+        // Let's look at how Ed25519.sign works. It derives 's' and 'prefix' from the seed.
+        
+        // For parity with Native implementation which returns [32pk | 64sk], 
+        // we need to be careful about what 'sk' means.
+        // In libsodium, sk is [32-byte seed | 32-byte public key].
+        // In Ed25519.java, it uses seed directly.
+        
+        // I will implement a bridge in Ed25519.java to handle this.
+        
+        // FOR NOW: Assume we follow libsodium: SK = [seed(32) | pub(32)]
+        byte[] sk = new byte[64];
+        System.arraycopy(seed, 0, sk, 0, 32);
+        System.arraycopy(pub, 0, sk, 32, 32);
+        
+        byte[] res = new byte[96];
+        System.arraycopy(pub, 0, res, 0, 32);
+        System.arraycopy(sk, 0, res, 32, 64);
+        return res;
+    }
+
+    @Override
+    public byte[] cryptoSignDetached(byte[] message, byte[] secretKey) {
+        // Assume secretKey is [seed(32) | pub(32)]
+        byte[] seed = new byte[32];
+        System.arraycopy(secretKey, 0, seed, 0, 32);
+        return Ed25519.sign(seed, message);
+    }
+}

src/main/java/swiss/qpq/gajumaru/core/tools/NodeClient.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option)
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>
@@ -20,32 +20,14 @@
 
 package swiss.qpq.gajumaru.core.tools;
 
-import java.io.BufferedReader;
-import java.io.InputStreamReader;
-import java.io.OutputStream;
-import java.net.HttpURLConnection;
-import java.net.URL;
-import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Map;
 import java.util.HashMap;
-import swiss.qpq.gajumaru.core.encoding.ZJ;
-
-
-// NodeClient provides a simple interface to query Gajumaru nodes.
-// Ported from hz.erl
-//
-// Conceptually very similar to Hakuzaru's main interface, but (at least currently)
-// more limited (no contract deployment, call, etc.). The most obvious difference is that
-// instead of gm-java being a stateful service the way hz can be, this is a pure library
-// and the caller is expected to be the one that is keeping track of a list of possible
-// endpoints.
-//
-// This design will evolve in the future as the concept of network and inter-network
-// crawling evolved (and obviously as ACs are introduced). In this iteration, though,
-// my goal is to keep things as simple as possible, and that is why this is probably
-// somewhat unidiomatic for Java (I don't *really* know, but this works).
 
+/**
+ * NodeClient provides a simple interface to query Gajumaru nodes.
+ * Ported from hz.erl
+ */
 public final class NodeClient {
 
     public static final class Endpoint {
@@ -65,7 +47,6 @@ public final class NodeClient {
     }
 
     private final List<Endpoint> endpoints;
-    private int timeout = 5000;
 
     public NodeClient(List<Endpoint> endpoints) {
         if (endpoints == null || endpoints.isEmpty()) {
@@ -74,23 +55,23 @@ public final class NodeClient {
         this.endpoints = endpoints;
     }
 
-    public void setTimeout(int timeout) {
-        this.timeout = timeout;
-    }
-
+    @SuppressWarnings("unchecked")
     public Map<String, Object> status() throws Exception {
         return (Map<String, Object>) request("/v3/status", "GET", null);
     }
 
+    @SuppressWarnings("unchecked")
     public long topHeight() throws Exception {
         Map<String, Object> res = (Map<String, Object>) request("/v3/headers/top", "GET", null);
         return ((Number) res.get("height")).longValue();
     }
 
+    @SuppressWarnings("unchecked")
     public Map<String, Object> account(String accountId) throws Exception {
         return (Map<String, Object>) request("/v3/accounts/" + accountId, "GET", null);
     }
 
+    @SuppressWarnings("unchecked")
     public long nextNonce(String accountId) throws Exception {
         try {
             Map<String, Object> res = (Map<String, Object>) request("/v3/accounts/" + accountId + "/next-nonce", "GET", null);
@@ -103,16 +84,19 @@ public final class NodeClient {
         }
     }
 
+    @SuppressWarnings("unchecked")
     public Map<String, Object> postTx(String signedTx) throws Exception {
         Map<String, String> body = new HashMap<>();
         body.put("tx", signedTx);
         return (Map<String, Object>) request("/v3/transactions", "POST", body);
     }
 
+    @SuppressWarnings("unchecked")
     public Map<String, Object> tx(String txHash) throws Exception {
         return (Map<String, Object>) request("/v3/transactions/" + txHash, "GET", null);
     }
 
+    @SuppressWarnings("unchecked")
     public Map<String, Object> txInfo(String txHash) throws Exception {
         return (Map<String, Object>) request("/v3/transactions/" + txHash + "/info", "GET", null);
     }
@@ -121,15 +105,19 @@ public final class NodeClient {
         Exception lastException = null;
         for (Endpoint endpoint : endpoints) {
             try {
+                String protocol = endpoint.useTls ? "https://" : "http://";
+                String url = protocol + endpoint.host + ":" + endpoint.port + path;
+                
                 if (endpoint.useTls) {
                     try {
-                        return performRequest(endpoint, path, method, body, true);
+                        return "GET".equals(method) ? Http.get(url) : Http.post(url, body);
                     } catch (Exception e) {
                         // Fallback to HTTP
-                        return performRequest(endpoint, path, method, body, false);
+                        String httpUrl = "http://" + endpoint.host + ":" + endpoint.port + path;
+                        return "GET".equals(method) ? Http.get(httpUrl) : Http.post(httpUrl, body);
                     }
                 } else {
-                    return performRequest(endpoint, path, method, body, false);
+                    return "GET".equals(method) ? Http.get(url) : Http.post(url, body);
                 }
             } catch (Exception e) {
                 lastException = e;
@@ -137,46 +125,4 @@ public final class NodeClient {
         }
         throw new Exception("All endpoints failed. Last error: " + (lastException != null ? lastException.getMessage() : "unknown"), lastException);
     }
-
-    private Object performRequest(Endpoint endpoint, String path, String method, Object body, boolean useTls) throws Exception {
-        String protocol = useTls ? "https://" : "http://";
-        String urlStr = protocol + endpoint.host + ":" + endpoint.port + path;
-        URL url = new URL(urlStr);
-        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
-        conn.setRequestMethod(method);
-        conn.setConnectTimeout(timeout);
-        conn.setReadTimeout(timeout);
-        conn.setRequestProperty("Accept", "application/json");
-
-        if (body != null) {
-            conn.setRequestProperty("Content-Type", "application/json");
-            conn.setDoOutput(true);
-            try (OutputStream os = conn.getOutputStream()) {
-                byte[] input = ZJ.encode(body).getBytes(StandardCharsets.UTF_8);
-                os.write(input, 0, input.length);
-            }
-        }
-
-        int code = conn.getResponseCode();
-        StringBuilder response = new StringBuilder();
-        try (BufferedReader br = new BufferedReader(new InputStreamReader(
-                code >= 200 && code < 300 ? conn.getInputStream() : conn.getErrorStream(), 
-                StandardCharsets.UTF_8))) {
-            String line;
-            while ((line = br.readLine()) != null) {
-                response.append(line.trim());
-            }
-        }
-
-        Object decoded = ZJ.decode(response.toString());
-        if (code < 200 || code >= 300) {
-            String reason = "HTTP " + code;
-            if (decoded instanceof Map) {
-                Object r = ((Map<?, ?>) decoded).get("reason");
-                if (r != null) reason = r.toString();
-            }
-            throw new Exception(reason);
-        }
-        return decoded;
-    }
 }

src/main/java/swiss/qpq/gajumaru/core/tools/SigningProvider.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
+ * Project: Gajumaru Core Java Libraries <gajumaru.io>
+ *
+ * This program is dual-licensed:
+ * 1) Under the GNU Affero General Public License as published by the Free
+ *    Software Foundation, either version 3 of the License, or (at your option)
+ *    any later version (AGPL-3.0-or-later).
+ *
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
+ *    If you wish to use this software outside the strict constraints of the
+ *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
+ *    purchase a commercial license from QPQ IaaS AG.
+ *
+ * Authors:
+ *   - Craig Everett <craigeverett@qpq.swiss>
+ *
+ * SPDX-License-Identifier: AGPL-3.0-or-later OR LicenseRef-QPQ-Commercial
+ */
+
+package swiss.qpq.gajumaru.core.tools;
+
+/**
+ * SigningProvider abstracts Ed25519 operations to allow different implementations
+ * (e.g., pure Java vs. Native libsodium) to be used at runtime.
+ */
+public interface SigningProvider {
+
+    /**
+     * Expands a 32-byte seed into a 64-byte secret key and 32-byte public key.
+     * @param seed 32-byte seed.
+     * @return 96-byte array [public_key(32) | secret_key(64)].
+     */
+    byte[] cryptoSignSeedKeypair(byte[] seed);
+
+    /**
+     * Signs a message using a 64-byte expanded secret key.
+     * @param message The data to sign.
+     * @param secretKey 64-byte secret key.
+     * @return 64-byte detached signature.
+     */
+    byte[] cryptoSignDetached(byte[] message, byte[] secretKey);
+}

src/main/java/swiss/qpq/gajumaru/core/tools/TransactionService.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2026 QPQ AG <info@qpq.swiss>. All rights reserved.
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
  * Project: Gajumaru Core Java Libraries <gajumaru.io>
  *
  * This program is dual-licensed:
@@ -7,10 +7,10 @@
  *    Software Foundation, either version 3 of the License, or (at your option)
  *    any later version (AGPL-3.0-or-later).
  *
- * 2) Under a commercial/proprietary license available directly from QPQ AG.
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
  *    If you wish to use this software outside the strict constraints of the
  *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
- *    purchase a commercial license from QPQ AG.
+ *    purchase a commercial license from QPQ IaaS AG.
  *
  * Authors:
  *   - Craig Everett <craigeverett@qpq.swiss>
@@ -30,13 +30,28 @@ import swiss.qpq.gajumaru.core.data.SignedTx;
 import swiss.qpq.gajumaru.core.data.SpendTx;
 import swiss.qpq.gajumaru.core.encoding.ApiEncoder;
 
-// This is where the gnarly mess used to generate transactions lives for now.
-// They might not stay here, but this is where they are for now.
-
+/**
+ * TransactionService provides high-level tools to build and sign transactions
+ * and other chain data.
+ */
 public final class TransactionService {
 
+    private static SigningProvider provider = new JavaSigningProvider();
+
     private TransactionService() {}
 
+    /**
+     * Sets the signing provider to use for all operations.
+     */
+    public static void setProvider(SigningProvider newProvider) {
+        if (newProvider != null) {
+            provider = newProvider;
+        }
+    }
+
+    /**
+     * Builds and signs a Spend transaction using a 32-byte seed.
+     */
     public static String buildSpendTx(
         String networkId,
         String senderId,
@@ -47,12 +62,11 @@ public final class TransactionService {
         long ttl,
         long nonce,
         String payload,
-        byte[] seckey
+        byte[] seed
     ) {
         // 1. Decode IDs
         Id sender = new Id(Id.Tag.ACCOUNT, ApiEncoder.decode(senderId).payload());
         
-        // Recipient can be ak_ (account) or ct_ (contract)
         ApiEncoder.DecodeResult recipientResult = ApiEncoder.decode(recipientId);
         Id.Tag recipientTag = recipientResult.type() == ApiEncoder.Type.CONTRACT_PUBKEY ? Id.Tag.CONTRACT : Id.Tag.ACCOUNT;
         Id recipient = new Id(recipientTag, recipientResult.payload());
@@ -69,13 +83,91 @@ public final class TransactionService {
         System.arraycopy(networkIdBytes, 0, networkHash, 0, networkIdBytes.length);
         System.arraycopy(txHash, 0, networkHash, networkIdBytes.length, txHash.length);
         
-        // 4. Sign
-        byte[] signature = Ed25519.sign(seckey, networkHash);
+        // 4. Expand Seed and Sign
+        byte[] keypair = provider.cryptoSignSeedKeypair(seed);
+        if (keypair == null) throw new RuntimeException("Signing provider keypair generation failed");
+        
+        byte[] secretKey = new byte[64];
+        System.arraycopy(keypair, 32, secretKey, 0, 64);
+        
+        byte[] signature = provider.cryptoSignDetached(networkHash, secretKey);
+        
+        CryptoUtils.wipe(keypair);
+        CryptoUtils.wipe(secretKey);
+        
+        if (signature == null) throw new RuntimeException("Native signing failed");
         
         // 5. Wrap in SignedTx
         SignedTx signedTx = new SignedTx(List.of(signature), serializedTx);
         
-        // 6. Encode for API
+        return ApiEncoder.encode(ApiEncoder.Type.TRANSACTION, signedTx.serialize());
+    }
+
+    /**
+     * Signs a message using the Gajumaru standard (prefixed and hashed).
+     * @param secretKey 64-byte expanded secret key.
+     */
+    public static byte[] signMessage(String message, byte[] secretKey) {
+        byte[] msgBytes = message.getBytes(StandardCharsets.UTF_8);
+        byte[] prefix = "Gajumaru Signed Message:\n".getBytes(StandardCharsets.UTF_8);
+        
+        byte[] pSize = VarInt.encode(prefix.length);
+        byte[] mSize = VarInt.encode(msgBytes.length);
+        
+        byte[] smashed = new byte[pSize.length + prefix.length + mSize.length + msgBytes.length];
+        int pos = 0;
+        System.arraycopy(pSize, 0, smashed, pos, pSize.length); pos += pSize.length;
+        System.arraycopy(prefix, 0, smashed, pos, prefix.length); pos += prefix.length;
+        System.arraycopy(mSize, 0, smashed, pos, mSize.length); pos += mSize.length;
+        System.arraycopy(msgBytes, 0, smashed, pos, msgBytes.length);
+        
+        byte[] hashed = Blake2b.hash(smashed, 32);
+        return provider.cryptoSignDetached(hashed, secretKey);
+    }
+
+    /**
+     * Signs binary data using the Gajumaru standard (prefixed and hashed).
+     * @param secretKey 64-byte expanded secret key.
+     */
+    public static byte[] signBinary(byte[] data, byte[] secretKey) {
+        byte[] prefix = "Gajumaru Signed Binary:".getBytes(StandardCharsets.UTF_8);
+        byte[] target = new byte[prefix.length + data.length];
+        System.arraycopy(prefix, 0, target, 0, prefix.length);
+        System.arraycopy(data, 0, target, prefix.length, data.length);
+        
+        byte[] hashed = Blake2b.hash(target, 32);
+        return provider.cryptoSignDetached(hashed, secretKey);
+    }
+
+    /**
+     * Verifies a binary signature.
+     */
+    public static boolean verifyBinary(byte[] data, byte[] signature, byte[] publicKey) {
+        byte[] prefix = "Gajumaru Signed Binary:".getBytes(StandardCharsets.UTF_8);
+        byte[] target = new byte[prefix.length + data.length];
+        System.arraycopy(prefix, 0, target, 0, prefix.length);
+        System.arraycopy(data, 0, target, prefix.length, data.length);
+        
+        byte[] hashed = Blake2b.hash(target, 32);
+        return Ed25519.verify(publicKey, hashed, signature);
+    }
+
+    /**
+     * Signs a transaction.
+     * @param secretKey 64-byte expanded secret key.
+     */
+    public static String signTx(byte[] txData, String networkId, byte[] secretKey) {
+        byte[] nidBytes = networkId.getBytes(StandardCharsets.UTF_8);
+        byte[] hash = Blake2b.hash(txData, 32);
+        
+        byte[] networkHash = new byte[nidBytes.length + hash.length];
+        System.arraycopy(nidBytes, 0, networkHash, 0, nidBytes.length);
+        System.arraycopy(hash, 0, networkHash, nidBytes.length, hash.length);
+        
+        byte[] signature = provider.cryptoSignDetached(networkHash, secretKey);
+        if (signature == null) throw new RuntimeException("Signing provider signing failed");
+        
+        SignedTx signedTx = new SignedTx(List.of(signature), txData);
         return ApiEncoder.encode(ApiEncoder.Type.TRANSACTION, signedTx.serialize());
     }
 }

src/main/java/swiss/qpq/gajumaru/core/tools/VarInt.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2026 QPQ IaaS AG <info@qpq.swiss>. All rights reserved.
+ * Project: Gajumaru Core Java Libraries <gajumaru.io>
+ *
+ * This program is dual-licensed:
+ * 1) Under the GNU Affero General Public License as published by the Free
+ *    Software Foundation, either version 3 of the License, or (at your option)
+ *    any later version (AGPL-3.0-or-later).
+ *
+ * 2) Under a commercial/proprietary license available directly from QPQ IaaS AG.
+ *    If you wish to use this software outside the strict constraints of the
+ *    AGPLv3 (e.g. within a closed-source or proprietary product), you must
+ *    purchase a commercial license from QPQ IaaS AG.
+ *
+ * Authors:
+ *   - Craig Everett <craigeverett@qpq.swiss>
+ *
+ * SPDX-License-Identifier: AGPL-3.0-or-later OR LicenseRef-QPQ-Commercial
+ */
+
+package swiss.qpq.gajumaru.core.tools;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+// Bitcoin-style Variable-length integer encoding.
+// Port of vencode in hz.erl.
+
+public final class VarInt {
+
+    private VarInt() {}
+
+    public static byte[] encode(long n) {
+        if (n < 0) {
+            throw new IllegalArgumentException("Negative values not supported: " + n);
+        }
+        if (n < 0xfd) {
+            return new byte[]{(byte) n};
+        } else if (n <= 0xffff) {
+            ByteBuffer bb = ByteBuffer.allocate(3);
+            bb.order(ByteOrder.LITTLE_ENDIAN);
+            bb.put((byte) 0xfd);
+            bb.putShort((short) n);
+            return bb.array();
+        } else if (n <= 0xffffffffL) {
+            ByteBuffer bb = ByteBuffer.allocate(5);
+            bb.order(ByteOrder.LITTLE_ENDIAN);
+            bb.put((byte) 0xfe);
+            bb.putInt((int) n);
+            return bb.array();
+        } else {
+            ByteBuffer bb = ByteBuffer.allocate(9);
+            bb.order(ByteOrder.LITTLE_ENDIAN);
+            bb.put((byte) 0xff);
+            bb.putLong(n);
+            return bb.array();
+        }
+    }
+}