A time notarization apparatus and method is disclosed which uses a secure, microprocessor based hardware platform which performs public kay cryptographic operations to obtain trusted time stamping with a minimum of intervention by third parties. The hardware platform is encapsulated in a secure fashion so that the device's timestamping mechanism may not be readily tampered with or altered. The hardware platform includes at least one digital clock (4) and a stable, secure storage device (8) to record the private half of a public/private key pair. Coupled to both the digital clock (4) and the storage device (8) is a data processing device (6) which performs public key signature operations in a secure and tamper-proof manner. Only the processing device (6) has access to the secure storage device (8) and its associated private key.; The hardware platform also includes input/output means which receives a digital message which is to be digitally signed and timestamped and which outputs the resulting timestamped signature generated by the device. The hadware platform also includes a power source (12), (e.g., an on-board battery) to ensure the accuracy of the device's digital clock (4) and the security of storage data prior to installation or in case of a power failure.