초록 ▼

A method and apparatus whereby the senders and receivers of messages sent over a transmission system including a Host CPU may guarantee the integrity of the data content of the message and also the absolute identity of the sender. Each user of the system as well as the Host CPU contains an identical

A method and apparatus whereby the senders and receivers of messages sent over a transmission system including a Host CPU may guarantee the integrity of the data content of the message and also the absolute identity of the sender. Each user of the system as well as the Host CPU contains an identical key-controlled block-cipher cryptographic device with data chaining for encrypting and decrypting messages as required, wherein each user has knowledge of only his own cryptographic key and wherein the Host CPU has access to the unique cryptographic keys of all users of the system stored in a high security storage area available only to said CPU. Stated very generally, the originator of a message A sends a message to a receiver B which includes a transaction or message portion X and a unique digital signature portion Y which is a function both of the message and the senders unique cryptographic key KA. The receiver then communicates with the CPU for verification of the signature Y. The CPU accesses the sender\s key KA from a secure memory and computes the digital signature Y utilizing the message portion X received from B and the key KA. Upon a successful verification of the signatures by the CPU, the CPU notifies B via an additional message that the signature of A is valid based on the data content of the message and the key KA. Based on the information received from the CPU, B may be certain that the signature and message originated with A and A may not later deny having sent the message as it would be virtually impossible for the signature to be forged since it is a complex function of the message content itself. A may also be assured that B cannot alter the message as the signature would no longer be valid. According to other aspects of the invention the interrupting of communications between A and B by an eavesdropper and the subsequent sending of stale messages is prevented. As a still further feature of the invention, an eavesdropper is prevented from sending the “forged”approval from the CPU to the receiver B.

대표청구항 ▼

A method for effecting a high security transaction verification operation in a computer based communications system comprising a central Host CPU which includes a high security Verify Unit (VAULT) therein said system including at least two remotely located terminals selectively connectable to said H

A method for effecting a high security transaction verification operation in a computer based communications system comprising a central Host CPU which includes a high security Verify Unit (VAULT) therein said system including at least two remotely located terminals selectively connectable to said Host CPU and wherein said Verify Unit and each of said terminals includes substantially identical key-controlled block cipher cryptographic devices with block chaining included therein said method comprising: User A (originator) at a first terminal sending User B (receiver) at a second terminal a message M having a data portion (X) and a signature portion (Y) said signature portion being a block cipher function of A\s key KA and the data portion (X), such that M=(X,Y); User B on receipt of the message (X,Y) reencrypting same under his own key KB to form a message U, sending said message U to the Host CPU together with the identities of User A and User B (originator, receiver), and requesting a verification operation from said Host CPU, the Host CPU, after receiving said message, obtaining the keys KA and KB from a secure storage means and decrypting U under key KB to obtain message U which presumptively comprises a message portion U1 and a signature portion U2; the Host CPU then forming a signature utilizing U1 as the data input and KA as the key input to the cryptographic device and comparing this signature with the signature value U2 received from User B, and the Host CPU returning an accept/reject signal to User B depending upon whether or not the two signatures are identical.