Certified transmission system

1. A method comprising:

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

verifying the signed receipt at the server;

transferring the verified receipt to a sender of the encrypted message; and

providing, from the server to a device associated with the intended recipient, a symmetric key corresponding to the encrypted symmetric key, the symmetric key generated by the sender of the encrypted message.

2. The method of claim 1 , further comprising:

receiving, from the sender, an encrypted message header associated with the encrypted message, the encrypted message header containing a first message identifier,

where providing the symmetric key includes:

decrypting the encrypted message header to retrieve the symmetric key and a second message identifier; and

providing the symmetric key to the intended recipient if the first message identifier and the second message identifier are equivalent.

3. The method of claim 1 , wherein:

receiving the signed receipt is performed at an application executing on the server;

verifying the signed receipt is performed by the application; and

transferring the verified receipt is performed by the application.

4. A method comprising:

encrypting a message using an encryption key;

sending, by a processor, the encrypted message to an intended recipient without the encryption key;

forwarding the encryption 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.

5. A method comprising:

encrypting a message using a symmetric key;

computing, by a processor, 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, by a time-stamping authority, the representation without exposing content of the message to the time-stamping authority.

6. The method of claim 5 , further comprising:

sending the representation to the time-stamping authority; and

receiving from the time-stamping authority a time stamp certificate including a time-stamped representation and a time.

7. The method of claim 5 , further comprising:

sending a request including the representation to the 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 of the message.

8. A method comprising:

receiving, at a server, a symmetric key from a sender of an encrypted message, the encrypted message being encrypted by the symmetric key;

receiving, at the server, a receipt from a recipient of the encrypted message;

determining, by a processor associated with the server, if the receipt has been signed by the recipient;

forwarding the receipt to the sender if it is determined that the receipt has been signed by the recipient; and

providing the symmetric key to the recipient to decrypt the encrypted message.

9. The method of claim 8 , where receiving the symmetric key includes:

receiving a message header associated with the encrypted message containing the symmetric key; and

decrypting the message header to retrieve the symmetric key.

10. The method of claim 9 , further comprising:

receiving a first message identifier associated with the encrypted message from the sender; and

receiving a second message identifier associated with the encrypted message from the recipient;

where determining if the receipt has been signed by the recipient includes determining if the first message identifier and the second message identifier are equivalent.

11. The method of claim 8 , further comprising:

receiving a representation of a hash of the symmetric key and the encrypted message encrypted by the symmetric key, the representation having been signed by the recipient indicating the receipt of the encrypted message.

12. The method of claim 11 , where receiving the representation includes:

receiving a time stamp certificate including a time of sending the encrypted message by the sender and a time of receiving the encrypted message by the recipient.

13. The method of claim 12 , where determining if the receipt has been signed by the recipient includes verifying the time stamp certificate based on the time of sending the encrypted message by the sender and the time of receiving the encrypted message by the recipient.

14. The method of claim 12 , where receiving the time stamp certificate further includes receiving a sender address of the sender and a recipient address of the recipient.

15. The method of claim 12 , further comprising:

verifying the time stamp certificate without accessing content of the encrypted message.

16. The method of claim 8 , further comprising:

receiving a first hash of the encrypted message from the sender; and

receiving a second hash of the encrypted message from the recipient,

where determining if the receipt has been signed by the recipient includes determining if the first hash and the second hash are equivalent.

17. The method of claim 8 , where providing the symmetric key includes providing the symmetric key to the recipient after transferring the signed receipt to the sender.

18. The method of claim 8 , where determining if the receipt has been signed by the recipient includes verifying the receipt without accessing content of the encrypted message.