Certified Transmission System

• US 20080155253A1
• Filed: 12/03/2007
• Published: 06/26/2008
• Est. Priority Date: 04/03/2001
• Status: Active Grant

• Current Assignee: Zix Corporation (Open Text Corporation)
• Original Assignee: Zix Corporation (Open Text Corporation)
• Inventors: Liu, Gary
• Granted Patent: US 8,027,923 B2
• Time in Patent Office: Days
• US Class Current: 713/155
• CPC Class Codes: G06Q 20/02 involving a neutral party, e.g. certification authority, notary or trusted third party [TTP]
• CPC Class Codes: G06Q 20/3823 combining multiple encryption tools for a transaction
• CPC Class Codes: G06Q 20/3829 involving key management
• CPC Class Codes: H04L 2209/56 Financial cryptography, e.g. electronic payment or e-cash
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

The invention provides a method and apparatus for transmitting a message from a sender to an intended recipient. The method includes encrypting a message using a symmetric key, sending the encrypted message to an intended recipient without the symmetric key and providing the symmetric key to a third party. If the intended recipient signs and returns to the third party a receipt for the message, the method includes transferring, by the third party, the receipt to the sender and providing the symmetric key to the intended recipient.

Claims

1. A computer-implemented method for certifying receipt of a message, the message being sent from a sender to an intended recipient and being encrypted by a symmetric key, and the method executing at a third party distinct from the sender and the intended recipient, the method comprising:

receiving a signed receipt and an encrypted symmetric key from the intended recipient, the signed receipt memorializing receipt of the encrypted message by the intended recipient;

verifying the signed receipt;

transferring the verified receipt to the sender; and

providing the symmetric key to the intended recipient.

2. A computer-implemented method, comprising:

encrypting a message using a symmetric key;

sending the encrypted message to an intended recipient without the symmetric key;

forwarding the encrypted symmetric key to a third party; and

receiving from the third party a certified receipt verified by the third party indicating receipt of the message by the intended recipient.

3. A computer-implemented method for time-stamping a message without exposing the content of the message to a time stamping authority, comprising:

encrypting the message using a symmetric key;

computing a hash of the symmetric key;

generating a representation of the hash of the symmetric key and the message encrypted by the symmetric key; and

time-stamping the representation.

4. The computer-implemented method of claim 3, wherein:

time-stamping the representation includes sending the representation to a time-stamping authority and receiving from the time-stamping authority a time stamp certificate including the representation and a time.

5. The computer-implemented method of claim 4, further comprising:

sending a request including the representation to a time stamping authority;

receiving from the time stamping authority a time stamp certificate including a time stamped representation of the hash of the symmetric key and the message encrypted by the symmetric key;

constructing a certified message including the time stamp certificate; and

sending the certified message to a recipient.

6. A computer-implemented method for computing a message identifier associated with a message comprising:

encrypting a message using a symmetric key to generate an encrypted message;

computing a hash of the symmetric key; and

generating a representation of the hash of the symmetric key and the encrypted message.

7. The computer-implemented method of claim 6, wherein generating the representation of the hash of the symmetric key and the encrypted message including using a one-way hash function.