Method of deriving a per-message signature for a DSS or El Gamal encryption system

Claim 2

A message authentication system of the type in which a signature of an originator of a message MSG, hereinafter the message originator, is transmitted to a recipient of the message and verified by the recipient, the message originator having a secret number S L and a corresponding public number P L , said system comprising: means for receiving the MSG; means for generating a secret message for each message, a per-message secret number, S M by applying a one-way hash function to a combination of MSG and a generated secret number of the message originator, means for generating a signature as a function of S L , S M and MSG.

Claim 3

The system defined in claim 1 further including: means for generating a per-message public number P M as a function of S M , and means for transmitting, to the recipient, the message, the signature and the per-message public number; means for receiving, by the recipient, the message, the signature and the per-message public number.

Claim 4

The system defined in claim 2 including means for the message recipient to verify the signature SIG in accordance with a function of MSG, SIG, P L and P M .

Claim 5

The system of claim 1 in which said one-way hash function is a message digest function.

Claim 6

A message authentication system comprising: A. a data terminal including: 1. means for receiving a message input and 2. means for communicating with a smart card, and B. the smart card configured to communicate with said terminal and including: 1. means for storing a secret number specific to an owner of the smart card, 2. means for generating a secret number for each message, hereinafter referred to as a per-message secret number by, applying a one-way hash function to a combination of (a) a secret number specific to the owner of the smart card and (b) a message received by said terminal by way of said message input means, 3. means for generating a signature as a function of said secret number, said per-message secret number and said message, 4. means for generating a per-message public number as a function of said per-message secret number; 5. means for transmitting to said terminal the signature and the per-message public number; and 6. means for verifying in the terminal.

Claim 7

A message authentication system comprising: A. a data terminal including: 1. means for receiving a message input and 2. means for communicating with a smart card, and B. the smart card configured to communicate with said terminal and including: 1. means for storing a secret number specific to an owner of the smart card, 2. means for generating a secret number for each message, hereinafter referred to as a per-message secret number by, applying a one-way hash function to a combination of (a) a secret number specific to the owner of the smart card and (b) a message received by said terminal by way of said message input means, 3. means for generating a signature as a function of said secret number, said per-message secret number and said message, 4. means for generating a per-message public number as a function of said per-message secret number; 5. means for transmitting to said terminal the signature and the per-message public number; and 6. means for verifying in the terminal.

Claim 8

The system defined in claim 5 in which said one-way hash function is a message digest function.

Claim 9

The system defined in claim 5 in which said combination is a concatenation of the secret number and the message.

Claim 10

A smart card for use in authenticating messages, said smart card including: A. means for storing a secret number specific to an owner of the smart card, B. means for receiving a message to be authenticated, C. means for generating a secret number for each message, hereinafter referred to as a per-message secret number, by applying a one-way hash function to a combination of said message and a secret number specific to said owner, D. means for generating a signature as a function of said secret number, said per-message secret number and said message, and E. means for transmitting said signature to a recipient.

Claim 11

A smart card for use in authenticating messages, said smart card including: A. means for storing a secret number specific to an owner of the smart card, B. means for receiving a message to be authenticated, C. means for generating a secret number for each message, hereinafter referred to as a per-message secret number, by applying a one-way hash function to a combination of said message and a secret number specific to said owner, D. means for generating a signature as a function of said secret number, said per-message secret number and said message, and E. means for transmitting said signature to a recipient.

Claim 12

The smart card defined in claim 8 in which said combination is a concatenation of said secret number and said message.

Claim 13

The smart card defined in claim 8 further including: A. means for generating a per-message public message as a function of said per-message secret number, and B. means for transmitting said per-message public number.

Claim 16

The method defined in claim 11 including the further steps of: A. generating a per-message public number as a function of the per-message secret number and B. transmitting said per-message public number to the recipient.