diff --git a/bin/create-memo.js b/bin/create-memo.js
index d75afda..64ef391 100755
--- a/bin/create-memo.js
+++ b/bin/create-memo.js
@@ -97,27 +97,32 @@ async function main() {
   console.info(`Fee:                ${feeDash} (${feeDuffs})`);
   //change.satoshis = sats;
 
-  let dashTx = DashTx.create({
-    /** @type {import('../dashtx.js').TxSign} */
+  /** @type {import('../dashtx.js').TxKeyUtils} */
+  let keyUtils = {
     sign: async function (privKeyBytes, hashBytes) {
       let sigOpts = { canonical: true };
       let sigBuf = await Secp256k1.sign(hashBytes, privKeyBytes, sigOpts);
       return sigBuf;
     },
+  getPublicKey: async function (txInput, i) {
+    let privKeyBytes = await keyUtils.getPrivateKey(txInput, i);
+    if (!privKeyBytes) {
+      return null;
+    }
+    let pubKeyBytes = await keyUtils.toPublicKey(privKeyBytes);
+
+    return pubKeyBytes;
+  },
     getPrivateKey: async function () {
       return privKeyBytes;
     },
-    toPublicKey:
-      /**
-       * @param {Uint8Array} privBytes
-       * @returns {Promise<Uint8Array>}
-       */
-      async function (privBytes) {
-        let isCompressed = true;
-        let pubBytes = Secp256k1.getPublicKey(privBytes, isCompressed);
-        return pubBytes;
-      },
-  });
+    toPublicKey: async function (privBytes) {
+      let isCompressed = true;
+      let pubBytes = Secp256k1.getPublicKey(privBytes, isCompressed);
+      return pubBytes;
+    },
+  };
+  let dashTx = DashTx.create(keyUtils);
 
   //@ts-ignore
   let txInfoSigned = await dashTx.hashAndSignAll(txInfo);
diff --git a/dashtx.js b/dashtx.js
index a53c080..ef4b5a7 100644
--- a/dashtx.js
+++ b/dashtx.js
@@ -56,6 +56,7 @@
 
 /**
  * @typedef TxUtils
+ * @prop {TxRPC} rpc
  * @prop {TxToVarInt} toVarInt
  * @prop {TxToVarIntSize} toVarIntSize
  * @prop {TxReverseHex} reverseHex
@@ -66,7 +67,7 @@
 
 /**
  * @callback TxCreate
- * @param {TxDeps} keyUtils
+ * @param {TxKeyUtils} keyUtils
  * @returns {tx}
  */
 
@@ -272,6 +273,9 @@ var DashTx = ("object" === typeof module && exports) || {};
         return pubKeyBytes;
       };
     }
+    /** @type {TxDeps} */
+    //@ts-ignore
+    let keyDeps = keyUtils;
 
     let txInst = {};
 
@@ -313,7 +317,7 @@ var DashTx = ("object" === typeof module && exports) || {};
 
       for (let i = 0; i < txInfo.inputs.length; i += 1) {
         let txInput = txInfo.inputs[i];
-        let privBytes = await keyUtils.getPrivateKey(txInput, i, txInfo.inputs);
+        let privBytes = await keyDeps.getPrivateKey(txInput, i, txInfo.inputs);
         if (privBytes) {
           txInput = await txInst.hashAndSignInput(
             privBytes,
@@ -358,7 +362,7 @@ var DashTx = ("object" === typeof module && exports) || {};
       let txBytes = Tx.utils.hexToBytes(txHex);
       let txHashBuf = await Tx.doubleSha256(txBytes);
 
-      let sigBuf = await keyUtils.sign(privBytes, txHashBuf);
+      let sigBuf = await keyDeps.sign(privBytes, txHashBuf);
       let sigHex = "";
       if ("string" === typeof sigBuf) {
         console.warn(`sign() should return a Uint8Array of an ASN.1 signature`);
@@ -369,7 +373,10 @@ var DashTx = ("object" === typeof module && exports) || {};
 
       let pubKeyHex = txInput.publicKey;
       if (!pubKeyHex) {
-        let pubKey = await keyUtils.getPublicKey(txInput, i, txInfo.inputs);
+        let pubKey = await keyDeps.getPublicKey(txInput, i, txInfo.inputs);
+        if (!pubKey) {
+          throw new Error(`no public key for input ${i}`);
+        }
         pubKeyHex = Tx.utils.bytesToHex(pubKey);
       }
       if ("string" !== typeof pubKeyHex) {
@@ -1693,14 +1700,7 @@ var DashTx = ("object" === typeof module && exports) || {};
     }
   }
 
-  /**
-   * @param {String} basicAuthUrl - ex: https://api:token@trpc.digitalcash.dev/
-   *                                    http://user:pass@localhost:19998/
-   * @param {String} method - the rpc, such as 'getblockchaininfo',
-   *                          'getaddressdeltas', or 'help'
-   * @param {...any} params - the arguments for the specific rpc
-   *                          ex: rpc(url, 'help', 'getaddressdeltas')
-   */
+  /** @type {TxRPC} */
   TxUtils.rpc = async function rpc(basicAuthUrl, method, ...params) {
     let url = new URL(basicAuthUrl);
     let baseUrl = `${url.protocol}//${url.host}${url.pathname}`;
@@ -1936,12 +1936,13 @@ if ("object" === typeof module) {
  */
 
 /**
- * @typedef TxDeps
+ * @typedef TxKeyUtils
  * @prop {TxGetPrivateKey} getPrivateKey
- * @prop {TxGetPublicKey} getPublicKey - efficiently get public key bytes
- * @prop {TxToPublicKey} [toPublicKey] - convert private bytes to pub bytes
+ * @prop {TxGetPublicKey} [getPublicKey] - efficiently get public key bytes
+ * @prop {TxToPublicKey} toPublicKey - convert private bytes to pub bytes
  * @prop {TxSign} sign
  */
+/** @typedef {Required<TxKeyUtils>} TxDeps */
 
 /**
  * @typedef TxFees
@@ -2157,17 +2158,17 @@ if ("object" === typeof module) {
 /**
  * @callback TxGetPrivateKey
  * @param {TxInputForSig} txInput
- * @param {Uint53} i
- * @param {Array<TxInputRaw|TxInputForSig>} txInputs
- * @returns {Promise<TxPrivateKey>} - private key Uint8Array
+ * @param {Uint53} [i]
+ * @param {Array<TxInputRaw|TxInputForSig>} [txInputs]
+ * @returns {Promise<TxPrivateKey?>} - private key Uint8Array
  */
 
 /**
  * @callback TxGetPublicKey
  * @param {TxInputForSig} txInput
- * @param {Uint53} i
- * @param {Array<TxInputRaw|TxInputForSig>} txInputs
- * @returns {Promise<TxPublicKey>} - public key Uint8Array
+ * @param {Uint53} [i]
+ * @param {Array<TxInputRaw|TxInputForSig>} [txInputs]
+ * @returns {Promise<TxPublicKey?>} - public key Uint8Array
  */
 
 /**
@@ -2356,6 +2357,16 @@ if ("object" === typeof module) {
  * @returns {Promise<TxPublicKey>} - public key buf
  */
 
+/**
+ * @callback TxRPC
+ * @param {String} basicAuthUrl - ex: https://api:token@trpc.digitalcash.dev/
+ *                                    http://user:pass@localhost:19998/
+ * @param {String} method - the rpc, such as 'getblockchaininfo',
+ *                          'getaddressdeltas', or 'help'
+ * @param {...any} params - the arguments for the specific rpc
+ *                          ex: rpc(url, 'help', 'getaddressdeltas')
+ */
+
 /**
  * Caution: JS can't handle 64-bit ints
  * @callback TxToVarInt