feat: Improve Nostr chat encryption with enhanced key validation and error handling

- Add validation for the hex format of private and public keys before encryption, ensuring they contain only valid characters.
- Implement error handling during the encryption process to log failures and provide clearer error messages.
- Refactor the encryption logic to improve reliability and security in the message encryption workflow.

src/composables/useNostrChat.ts

@@ -403,22 +403,28 @@ export function useNostrChat() {
         throw new Error(`Invalid public key length: ${publicKey.length} (expected 64)`)
       }
       
-      console.log('Encrypting message with keys:', {
+      // Validate hex format
-        privateKeyLength: privateKey.length,
+      const hexRegex = /^[0-9a-fA-F]+$/
-        publicKeyLength: publicKey.length,
+      if (!hexRegex.test(privateKey)) {
-        privateKeyPrefix: privateKey.slice(0, 8) + '...',
+        throw new Error(`Invalid private key format: contains non-hex characters`)
-        publicKeyPrefix: publicKey.slice(0, 8) + '...',
+      }
-        contentLength: content.length
+      
-      })
+      if (!hexRegex.test(publicKey)) {
+        throw new Error(`Invalid public key format: contains non-hex characters`)
+      }
       
       // Encrypt the message
-      const encryptedContent = await nip04.encrypt(
+      let encryptedContent: string
-        privateKey,
+      try {
-        publicKey,
+        encryptedContent = await nip04.encrypt(
-        content
+          privateKey,
-      )
+          publicKey,
-      
+          content
-      console.log('Message encrypted successfully, length:', encryptedContent.length)
+        )
+      } catch (encryptError) {
+        console.error('Encryption failed:', encryptError)
+        throw new Error(`Encryption failed: ${encryptError instanceof Error ? encryptError.message : String(encryptError)}`)
+      }
 
       // Create the event template
       const eventTemplate: EventTemplate = {