Feat/certificate (#68)

* feat: implement certificate encoding and decoding functionality with AES encryption

* feat: blank cert

* Refactor code structure for improved readability and maintainability

apps/hackathon/src/utils/certificate.ts

@@ -0,0 +1,41 @@
+import { decryptText, encryptText } from "./aesclient";
+
+const SECRET_KEY = 'imphnen-hackathon-2025';
+
+/**
+ * Encode teamId and submissionId into a certificate ID
+ * Uses base64 encoding for simple obfuscation
+ * @param teamId - The team ID
+ * @param submissionId - The submission ID
+ * @returns Encoded certificate ID
+ */
+export const encodeCertificateId = async (teamId: string, submissionId: string): Promise<string> => {
+  const combined = `${teamId}::${submissionId}`;
+  return encryptText(combined, SECRET_KEY);
+};
+
+/**
+ * Decode certificate ID back to teamId and submissionId
+ * @param certId - The encoded certificate ID
+ * @returns Object containing teamId and submissionId
+ */
+export const decodeCertificateId = async (certId: string): Promise<{ teamId: string; submissionId: string }> => {
+  try {
+    const decoded = await decryptText(certId, SECRET_KEY);
+    const [teamId, submissionId] = decoded.split('::');
+    return { teamId, submissionId };
+  } catch {
+    throw new Error('Invalid certificate ID');
+  }
+};
+
+/**
+ * For development: Create a certId using created_at timestamp
+ * @param teamId - The team ID
+ * @param createdAt - The creation timestamp
+ * @returns Encoded certificate ID
+ */
+export const encodeCertificateIdWithTimestamp = (teamId: string, createdAt: string): string => {
+  const combined = `${teamId}::${createdAt}`;
+  return Buffer.from(combined).toString('base64');
+};