The Timestamping Authority (TSA) solution processes timestamp requests to provide proof that a digital document, message, or transaction:

• Existed at a specific point in time
• Has not been altered since that time

To fulfill these requests, the system relies on the following components:

• Multiple clients send timestamp requests to the Timestamping Authority service
• One or more Hardware Security Modules (HSMs) securely manage the timestamp signing keys
• One or more Network Time Protocol (NTP) servers provide an accurate and reliable time source 

  The Timestamping Authority returns timeNotAvailable responses when no reliable time source is available.