Let's break down the most common causes and fixes for this frustrating error—poloniex's API is pretty strict about signature and key formatting, so small missteps here often trigger 403s.

1. Double-Check Your API Key/Secret Basics #

First, rule out the obvious:

• Go directly to your Poloniex account's API settings and verify you've copied the full, exact API Key and Secret—no extra spaces, missing characters, or accidental line breaks. It's easy to miss a character when copying/pasting!
• Ensure the API key hasn't been revoked, expired, or restricted to specific IP addresses (Poloniex lets you set IP whitelists; if your current IP isn't on that list, you'll get this error immediately).
• Confirm the key has the necessary permissions for the endpoint you're calling (e.g., if you're trying to check balances, the "Read" permission must be enabled; for trades, "Trade" needs to be toggled on).

2. Fix Your HMAC Signature Generation (The Most Likely Culprit) #

Poloniex's signature validation hinges on generating the HMAC-SHA512 hash correctly from the raw request body and your API secret. Here's where people usually mess up:

Correct Pre-Request Script Example

If you're using x-www-form-urlencoded body (Poloniex's preferred format for private endpoints):

// Pull secret from Postman environment variables (always use env vars instead of hardcoding!)
const apiSecret = pm.environment.get("POLONIEX_API_SECRET");

// Get the raw form data and encode it properly (matching what Poloniex expects)
const formData = pm.request.body.formdata;
const encodedBody = formData.map(item => `${encodeURIComponent(item.key)}=${encodeURIComponent(item.value)}`).join('&');

// Generate HMAC-SHA512 signature
const hmac = CryptoJS.HmacSHA512(encodedBody, apiSecret);
const hmacHex = hmac.toString(CryptoJS.enc.Hex);

// Store signature in an env var to use in headers
pm.environment.set("POLONIEX_SIGNATURE", hmacHex);

Critical Checks for Signature Logic:

• Never use parsed JSON to generate the signature—Poloniex validates against the raw, URL-encoded string of your request body. If you're using JSON body, make sure you're grabbing pm.request.body.raw instead of parsing it.
• Include a unique nonce parameter in your body (use {{$timestamp}} in Postman to auto-generate a fresh timestamp each request). Poloniex requires this to prevent replay attacks, and omitting it or reusing a nonce will trigger the invalid key error.

3. Verify Header Configuration #

Poloniex expects two specific headers—get these wrong, and your signature will be rejected:

• Key: Set this to your API Key (use an environment variable like {{POLONIEX_API_KEY}} for safety).
• Sign: Set this to the HMAC signature you generated in the pre-request script (e.g., {{POLONIEX_SIGNATURE}}).

Important: Header names are case-sensitive! Don't use API-Key or Signature—stick exactly to Key and Sign.

4. Cross-Check Request Format #

• Private Poloniex endpoints must use POST requests—GET requests will always return 403 for authenticated endpoints.
• Ensure your body format matches what you're using in the signature script. If you're using x-www-form-urlencoded, don't switch to JSON mid-test without updating the pre-request logic to handle raw JSON strings.

Final Test: Isolate the Issue #

If you're still stuck, try running a simple curl command to rule out Postman-specific issues:

curl https://poloniex.com/tradingApi \
  -H "Key: YOUR_API_KEY" \
  -H "Sign: $(echo -n 'command=returnBalances&nonce=$(date +%s)' | openssl dgst -sha512 -hmac YOUR_API_SECRET)" \
  -d "command=returnBalances&nonce=$(date +%s)"

If this works, the problem is in your Postman setup (likely signature generation or header formatting). If it fails, double-check your API key/secret permissions in Poloniex.

内容的提问来源于stack exchange，提问作者Sai