Electrical computers and digital processing systems: multicomput – Computer conferencing – Demand based messaging
Reexamination Certificate
1999-06-28
2004-07-06
Von Buhr, Maria N. (Department: 2125)
Electrical computers and digital processing systems: multicomput
Computer conferencing
Demand based messaging
C713S156000, C713S170000
Reexamination Certificate
active
06760752
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to computing systems and more particularly to a method and system for providing secure data transmissions between Internet users.
BACKGROUND OF THE INVENTION
The Internet is a global network of computers that uses a common communication protocol, the Transfer Control Protocol/Internet Protocol (TCP/IP), to transmit data from one location to another. Many application specific tasks, such as E-mail transmission and file transfer, are not directly supported by TCP/IP. Instead, support for these services is implemented by application specific protocols that in turn rely on TCP/IP for basic data transport services. One problem that is relatively unknown to individuals that make use of the Internet is the ease by which information can be obtained during transmission by unauthorized eavesdroppers. For example, most E-mail transmissions over the Internet are sent in cleartext. Cleartext is unencrypted data that can be intercepted anywhere along the path between a sender and the recipient.
Accordingly, sensitive business or personal information should not be transmitted in cleartext over the Internet. To do so is to risk its publication. To avoid this risk, sensitive data is often sent by courier services at great cost.
Encryption mechanisms can be used to ensure the integrity of information sent over the Internet. Two common encryption techniques, symmetric key encryption and public key encryption, are described below. In a symmetric key encryption, a unique key is identified and used by the sender to encrypt and by the receiver to decrypt a message. In public key encryption, separate keys are used to encrypt and to decrypt a message.
While secure communications are desirable, the mechanisms required to ensure security can be difficult to implement in a network environment. Private networks that include connections to public networks are often shielded using a firewall. A firewall provides a gateway between a public and a private network, or between public and private portions of a single network. A firewall can screen incoming and outgoing traffic to ensure integrity of the traffic between the two distinct domains. While the screening is desirable to avoid unauthorized access to or transfers of data, the additional security measures can have undesirable effects in limiting the kind or form of traffic that is able easily to be transmitted through the gateway.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a method for transferring a message securely from a sender to a recipient over a network and includes at each transfer: creating a message; retrieving the public key of the recipient from an external key server just prior to sending the message; signing the message using the private key of the sender; encrypting the signed message using a public key encryption algorithm and the public key of the recipient producing an encrypted signed message; generating an E-mail message addressed to the recipient; attaching the encrypted signed message as an attachment to the E-mail message; and, transmitting the E-mail message to the recipient.
Aspects of the invention can include one or more of the following features. The step of retrieving the public key of the recipient can include verifying a status of a public key for the sender and where the external key server is operable to not return the recipient's public key unless the status of the sender's public key is active.
Verifying the status of a public key of the sender can include sending a hash of a sender's public key to a external key server where the external key server is operable to maintain a status for each public key stored therein and enabled to return the status for a particular public key when the hash is received.
The external key server can be a single central key server. The external key server can be one of a group of external key servers each including a repository of public keys.
Substantially contemporaneous with sending the message, the method can include prompting the sender for a signature phrase, decrypting the private key of the sender using the signature phrase, applying a hash function to a sender's public key to produce a hash and verifying a status of the sender's public key including submitting the hash to the external key server to enable a look-up of a status of a public key of the sender.
The method can include designating a signature phrase by each user, either sender or recipient, encrypting a private key of the user using the signature phrase and storing the encrypted private key locally at a user's computer.
The step of retrieving the public key of the recipient can include generating a request for a current public key of the recipient where the request can include an identifier for the recipient.
The identifier can be an E-mail address for the recipient or a hash of an E-mail address for the recipient.
The step of encrypting can include generating a random number, encrypting the message using the random number as a session key in a symmetric key encryption algorithm and encrypting the session key using a public key encryption algorithm and the public key of the recipient.
The step of signing a message can include decrypting a private key of the sender and applying a digital signature algorithm to the message using the sender's private key.
The step of decrypting the private key can includes prompting the user for a signature phrase, applying a hash function to the signature phrase and decrypting the private key using a symmetric key encryption algorithm where the hash is used as the symmetric key.
The step of attaching the signed document can include designating a recipient's E-mail address and the sender's E-mail address, designating one or more of a public title and public message body for the E-mail message and attaching the encrypted signed message as an attachment to the E-mail message addressed to the recipient.
The step of transmitting can include transmitting the E-mail message to a forwarding proxy using a non-SMTP protocol where the forwarding proxy is operable to extract the E-mail message and forward the E-mail message to the recipient. The non-SMTP protocol can be the HTTP protocol.
The method can include creating an HTTP post including the E-mail message and transmitting the HTTP post. The forwarding proxy can forward the E-mail message by SMTP.
The method can include attaching a random number to the E-mail message prior to transferring where the forwarding proxy is operable to verify the random number is valid based on a predefined criterion, and if not, will not forward the E-mail message. The predefined criterion can be the passage of a predefined amount of time.
The method can include attaching a return receipt request to the E-mail message and acknowledging the return of a receipt including displaying the receipt to the sender. The opening of the E-mail message by the recipient can be conditioned upon the return of the return receipt.
The step of generating an E-mail message can include creating a MIME E-mail message addressed to the recipient. The step of attaching the signed document can include attaching the signed document to the MIME mail message as a MIME attachment. The step of transmitting can include sending the MIME mail message to the recipient.
The central key server can be one of a plurality of distributed key servers, each of which include public keys and status information to enable key retrieval from multiple locations, which facilitates secure transfers of messages between users.
In another aspect, the invention provides a method for transferring E-mail messages securely from a sender to a recipient over a network including, substantially contemporaneous with the transmission of a secure E-mail transmission from the sender to the recipient, retrieving the public key of the recipient from an external key server to ensure an active public key for the recipient is used in encrypting the message.
Aspects of the invention can include one or more of the followin
Cook David P.
Liu Gary G.
Fish & Richardson P.C.
Von Buhr Maria N.
Zix Corporation
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