Every REST API method includes a required parameter called ‘nonce’. In security engineering, a nonce is an abbreviation of number used once. The purpose of this parameter is to to ensure that old communications cannot be reused in replay attacks. Gigya requires that in each REST API call the nonce string will be unique. If Gigya receives two API calls with the same nonce, the second APi call will be rejected with the “Duplicate nonce” error (code 403004).