Kalshi API Integration Guide

import os
import time
import base64
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import padding
import requests

# Load credentials
API_KEY_ID = os.environ['KALSHI_API_KEY_ID']
PRIVATE_KEY_PEM = os.environ['KALSHI_PRIVATE_KEY']
BASE_URL = 'https://api.elections.kalshi.com'

# Parse private key
private_key = serialization.load_pem_private_key(
    PRIVATE_KEY_PEM.encode(),
    password=None
)

def create_signature(method: str, path: str):
    """Generate Kalshi API signature headers"""
    timestamp = str(int(time.time() * 1000))
    message = f"{timestamp}{method}{path}"

    # Sign with RSA-PSS
    signature = private_key.sign(
        message.encode(),
        padding.PSS(
            mgf=padding.MGF1(hashes.SHA256()),
            salt_length=padding.PSS.MAX_LENGTH
        ),
        hashes.SHA256()
    )

    # Base64 encode
    signature_b64 = base64.b64encode(signature).decode()

    return {
        'KALSHI-ACCESS-KEY': API_KEY_ID,
        'KALSHI-ACCESS-TIMESTAMP': timestamp,
        'KALSHI-ACCESS-SIGNATURE': signature_b64
    }

# Example: Get all portfolio fills (with pagination)
def get_all_fills():
    all_fills = []
    cursor = None

    while True:
        path = '/trade-api/v2/portfolio/fills'
        if cursor:
            path += f'?cursor={cursor}'

        headers = create_signature('GET', path)
        response = requests.get(f"{BASE_URL}{path}", headers=headers)
        data = response.json()

        all_fills.extend(data.get('fills', []))
        cursor = data.get('cursor')
        if not cursor:
            break

    return all_fills

fills = get_all_fills()
print(f"Fetched {len(fills)} fills")

import crypto from 'crypto';
import axios from 'axios';

const API_KEY_ID = process.env.KALSHI_API_KEY_ID!;
const PRIVATE_KEY_PEM = process.env.KALSHI_PRIVATE_KEY!;
const BASE_URL = 'https://api.elections.kalshi.com';

function createSignature(method: string, path: string) {
  const timestamp = Date.now().toString();
  const message = `${timestamp}${method}${path}`;

  // Sign with RSA-PSS
  const signature = crypto.sign(
    'sha256',
    Buffer.from(message),
    {
      key: PRIVATE_KEY_PEM,
      padding: crypto.constants.RSA_PKCS1_PSS_PADDING,
      saltLength: crypto.constants.RSA_PSS_SALTLEN_DIGEST,
    }
  );

  // Base64 encode
  const signatureB64 = signature.toString('base64');

  return {
    'KALSHI-ACCESS-KEY': API_KEY_ID,
    'KALSHI-ACCESS-TIMESTAMP': timestamp,
    'KALSHI-ACCESS-SIGNATURE': signatureB64,
  };
}

// Example: Get all portfolio fills (with pagination)
async function getAllFills() {
  const allFills = [];
  let cursor: string | undefined;

  while (true) {
    const path = '/trade-api/v2/portfolio/fills' + (cursor ? `?cursor=${cursor}` : '');
    const headers = createSignature('GET', path);

    const response = await axios.get(`${BASE_URL}${path}`, { headers });
    const data = response.data;

    allFills.push(...(data.fills || []));
    cursor = data.cursor;
    if (!cursor) break;
  }

  return allFills;
}

getAllFills().then(fills => console.log(`Fetched ${fills.length} fills`));