diff --git a/.gitignore b/.gitignore
index 490f098..737d98a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,3 +12,4 @@ coverage
 ts-adv-trade-test-private.ts
 examples/ts-app-priv.ts
 examples/ts-commerce.ts
+ts-exchange-priv.ts
diff --git a/src/CBAppClient.ts b/src/CBAppClient.ts
index f6fe4c4..92b24ba 100644
--- a/src/CBAppClient.ts
+++ b/src/CBAppClient.ts
@@ -34,6 +34,8 @@ export class CBAppClient extends BaseRestClient {
     super(restClientOptions, {
       ...requestOptions,
       headers: {
+        // Some endpoints return a warning if a version header isn't included: https://docs.cdp.coinbase.com/coinbase-app/docs/versioning
+        // Currently set to a date from the changelog: https://docs.cdp.coinbase.com/coinbase-app/docs/changelog
         'CB-VERSION': '2024-09-13',
         ...requestOptions.headers,
       },
diff --git a/src/lib/BaseRestClient.ts b/src/lib/BaseRestClient.ts
index 11faebe..64579f3 100644
--- a/src/lib/BaseRestClient.ts
+++ b/src/lib/BaseRestClient.ts
@@ -351,8 +351,9 @@ export abstract class BaseRestClient {
       requestOptions: {
         ...this.options,
         // Prevent credentials from leaking into error messages
-        apiKeyName: 'omittedFromError',
-        apiPrivateKey: 'omittedFromError',
+        apiKey: 'omittedFromError',
+        apiSecret: 'omittedFromError',
+        apiPassphrase: 'omittedFromError',
         cdpApiKey: 'omittedFromError',
       },
       requestParams,
@@ -385,6 +386,7 @@ export abstract class BaseRestClient {
 
     const apiKey = this.apiKey;
     const apiSecret = this.apiSecret;
+    const apiPassphrase = this.apiPassphrase;
     const jwtExpiresSeconds = this.options.jwtExpiresSeconds || 120;
 
     if (!apiKey) {
@@ -448,9 +450,12 @@ export abstract class BaseRestClient {
           // See: https://github.com/tiagosiebler/coinbase-api/issues/24
         }
 
-        case REST_CLIENT_TYPE_ENUM.exchange: {
-          // Docs: https://docs.cdp.coinbase.com/exchange/docs/rest-auth
-          const timestampInSeconds = timestampInMs / 1000;
+        // Docs: https://docs.cdp.coinbase.com/exchange/docs/rest-auth
+        case REST_CLIENT_TYPE_ENUM.exchange:
+
+        // Docs: https://docs.cdp.coinbase.com/intx/docs/rest-auth
+        case REST_CLIENT_TYPE_ENUM.international: {
+          const timestampInSeconds = timestampInMs / 1000; // decimals are OK
 
           const signInput =
             timestampInSeconds + method + endpoint + requestBodyString;
@@ -459,7 +464,7 @@ export abstract class BaseRestClient {
             throw new Error(`No API secret provided, cannot sign request.`);
           }
 
-          if (!this.apiPassphrase) {
+          if (!apiPassphrase) {
             throw new Error(`No API passphrase provided, cannot sign request.`);
           }
 
@@ -468,13 +473,14 @@ export abstract class BaseRestClient {
             apiSecret,
             'base64',
             'SHA-256',
+            'base64:web',
           );
 
           const headers = {
+            'CB-ACCESS-KEY': apiKey,
             'CB-ACCESS-SIGN': sign,
             'CB-ACCESS-TIMESTAMP': timestampInSeconds,
-            'CB-ACCESS-PASSPHRASE': this.apiPassphrase,
-            'CB-ACCESS-KEY': apiKey,
+            'CB-ACCESS-PASSPHRASE': apiPassphrase,
           };
 
           return {
@@ -486,16 +492,16 @@ export abstract class BaseRestClient {
             },
           };
 
-          // TODO: is there demand for FIX
+          // For CB Exchange, is there demand for FIX
           // Docs, FIX: https://docs.cdp.coinbase.com/exchange/docs/fix-connectivity
-        }
 
-        // Docs: https://docs.cdp.coinbase.com/intx/docs/rest-auth
-        case REST_CLIENT_TYPE_ENUM.international:
+          // For CB International, is there demand for FIX
+          // Docs, FIX: https://docs.cdp.coinbase.com/intx/docs/fix-overview
+        }
 
         // Docs: https://docs.cdp.coinbase.com/prime/docs/rest-authentication
         case REST_CLIENT_TYPE_ENUM.prime: {
-          const timestampInSeconds = String(Math.floor(timestampInMs / 1000));
+          const timestampInSeconds = Math.floor(timestampInMs / 1000); // decimal not allowed
 
           const signInput =
             timestampInSeconds + method + endpoint + requestBodyString;
@@ -504,7 +510,7 @@ export abstract class BaseRestClient {
             throw new Error(`No API secret provided, cannot sign request.`);
           }
 
-          if (!this.apiPassphrase) {
+          if (!apiPassphrase) {
             throw new Error(`No API passphrase provided, cannot sign request.`);
           }
 
@@ -513,15 +519,19 @@ export abstract class BaseRestClient {
             apiSecret,
             'base64',
             'SHA-256',
+            'base64:web',
           );
 
           const headers = {
-            'CB-ACCESS-TIMESTAMP': timestampInSeconds,
-            'CB-ACCESS-SIGN': sign,
-            'CB-ACCESS-PASSPHRASE': this.apiPassphrase,
-            'CB-ACCESS-KEY': apiKey,
+            'X-CB-ACCESS-KEY': apiKey,
+            'X-CB-ACCESS-PASSPHRASE': apiPassphrase,
+            'X-CB-ACCESS-SIGNATURE': sign,
+            'X-CB-ACCESS-TIMESTAMP': timestampInSeconds,
           };
 
+          // For CB Prime, is there demand for FIX
+          // Docs, FIX: https://docs.cdp.coinbase.com/prime/docs/fix-connectivity
+
           return {
             ...res,
             sign: sign,
@@ -530,12 +540,6 @@ export abstract class BaseRestClient {
               ...headers,
             },
           };
-
-          // For CB International, is there demand for FIX
-          // Docs, FIX: https://docs.cdp.coinbase.com/intx/docs/fix-overview
-
-          // For CB Prime, is there demand for FIX
-          // Docs, FIX: https://docs.cdp.coinbase.com/prime/docs/fix-connectivity
         }
         case REST_CLIENT_TYPE_ENUM.commerce: {
           // https://docs.cdp.coinbase.com/commerce-onchain/docs/getting-started
diff --git a/src/lib/webCryptoAPI.ts b/src/lib/webCryptoAPI.ts
index 0d9272b..9c8ff5e 100644
--- a/src/lib/webCryptoAPI.ts
+++ b/src/lib/webCryptoAPI.ts
@@ -10,6 +10,17 @@ function bufferToB64(buffer: ArrayBuffer): string {
   return globalThis.btoa(binary);
 }
 
+function b64StringToBuffer(input: string): ArrayBuffer {
+  const binaryString = atob(input); // Decode base64 string
+  const buffer = new Uint8Array(binaryString.length);
+
+  // Convert binary string to a Uint8Array
+  for (let i = 0; i < binaryString.length; i++) {
+    buffer[i] = binaryString.charCodeAt(i);
+  }
+  return buffer;
+}
+
 export type SignEncodeMethod = 'hex' | 'base64';
 export type SignAlgorithm = 'SHA-256' | 'SHA-512';
 
@@ -51,12 +62,33 @@ export async function signMessage(
   secret: string,
   method: SignEncodeMethod,
   algorithm: SignAlgorithm,
+  secretEncodeMethod: 'base64:web' | 'utf',
 ): Promise<string> {
   const encoder = new TextEncoder();
 
+  let encodedSecret;
+
+  switch (secretEncodeMethod) {
+    // case 'base64:node': {
+    //   encodedSecret = Buffer.from(secret, 'base64');
+    //   break;
+    // }
+    case 'base64:web': {
+      encodedSecret = b64StringToBuffer(secret);
+      break;
+    }
+    case 'utf': {
+      encodedSecret = encoder.encode(secret);
+      break;
+    }
+    default: {
+      throw new Error(`Unhandled encoding: "${secretEncodeMethod}"`);
+    }
+  }
+
   const key = await globalThis.crypto.subtle.importKey(
     'raw',
-    encoder.encode(secret),
+    encodedSecret,
     { name: 'HMAC', hash: algorithm },
     false,
     ['sign'],