System and method using information-based indicia for securing and authenticating transactions

A system for generating information-based indicia for a user's desired transaction, comprising one or more computers configured to:

• a) receive as input a nonce from a nonce stamp of the user, wherein the nonce comprises a relatively unique number selected randomly from a distribution sufficient to substantially prevents a single user from accumulating multiple nonce stamps bearing the same nonce;
• b) encrypt the nonce using an encryption key, the encryption key being unrecoverable without knowledge in addition to knowledge of the nonce;
• and
• c) provide to the user a digital certificate comprising at least the encrypted nonce, wherein the nonce is received via the fence stamp prior to deriving the digital certificate, and whereby the nonce stamp and the digital certificate may be collectively presented as an information-based indicium for the desired transaction.

A system for authenticating a postal transaction comprising:

• a) a forgery-resistant postage stamp bearing a first number, the first number being at least partially readable without special-purpose hardware, wherein the first number comprises a relatively unique number selected randomly from a distribution sufficient to substantially prevents a single user from accumulating multiple postage stamps bearing the same first number;
• and
• b) at least one computer adapted to receive the first number and to generate a digital certificate derived at least in part from the first number using an encryption key, the encryption key being unrecoverable without knowledge in addition to knowledge of the nonce;
• wherein the postage stamp and digital certificate may be collectively presented for authenticating a postal transaction by comparing the first number to the digital certificate.