diff --git a/main-site/server.js b/main-site/server.js
index 3320ea2..7395380 100644
--- a/main-site/server.js
+++ b/main-site/server.js
@@ -106,7 +106,8 @@ apiRouter.get('/altcha', async (req, res) => {
     try {
         const challenge = await createChallenge({
             algorithm: 'SHA-256',
-            cost: 100,
+            cost: 50000,
+            expiresAt: new Date(Date.now() + 10 * 60 * 1000), // 10 minutes
             deriveKey: altchaSha.deriveKey,
             hmacSignatureSecret: process.env.ALTCHA_HMAC_KEY || 'dev-key-change-in-production',
         });