Cryptographic module for secure processing of value-bearing items

A system for securing data in a computer network comprising:

• a server system configured to communicate with a plurality of client systems via the computer network, the server system including a plurality of cryptographic devices, each cryptographic device comprising:
• a processor programmed to authenticate the plurality of users on the computer network for generating a postal indicium, using a plurality of challenges;
• a memory for storing a data record for ensuring authenticity of a respective one of the plurality of users, the data record including a key for encrypting a user secret, a private key for signing the challenges, and a last challenge received from a client subsystem of the respective user;
• a cryptographic engine for cryptographically protecting the data record;
• and
• an interface for communicating with the computer network, wherein when a respective cryptographic device receives a new challenge message from the client subsystem, the processor is configured to respond by signing the received challenge with the stored private key and send a ciphertext back to the client subsystem to be compared with the new challenge message.