Method and apparatus for verifying secure document timestamping

Abstract

According to one embodiment of the invention, a method is provided for receiving a timestamp from a caller via a telephone connection; receiving a device identifier from the caller, in which the device identifier identifies a device; determining a cryptographic key based on the device identifier; determining an indication of a time based on the timestamp and the cryptographic key; providing the indication of the time to the caller; determining an account; and charging a fee to the account.

1. A method comprising:
 receiving a timestamp from a caller via a telephone connection;   receiving a device identifier from the caller, in which the device identifier identifies a device;   determining a cryptographic key based on the device identifier;   determining a representation of a time based on the timestamp and the cryptographic key;   providing the representation of the time to the caller;   determining an account; and   charging a fee to the account.   
     
     
       2. The method of  claim 1 , in which the timestamp is optically detectable on a physical document. 
     
     
       3. The method of  claim 1 , in which receiving the timestamp comprises:
 receiving the timestamp at a central controller.   
     
     
       4. The method of  claim 1 , further comprising:
 receiving a telephone call from the caller.   
     
     
       5. The method of  claim 1 , in which receiving the timestamp comprises:
 receiving a sequence of DTMF signals; and   determining the timestamp based on the DTMF signals.   
     
     
       6. The method of  claim 5 , in which the sequence is entered by the caller at a keypad. 
     
     
       7. The method of  claim 1 , in which receiving the timestamp comprises:
 receiving a sequence of signals via an interactive response unit (IRU).   
     
     
       8. The method of  claim 1 , in which receiving the timestamp comprises:
 receiving the timestamp via a toll-based telephone line.   
     
     
       9. The method of  claim 8 , in which the toll-based telephone line is associated with a 900 number. 
     
     
       10. The method of  claim 1 , in which the timestamp comprises a sequence of alphanumeric characters. 
     
     
       11. The method of  claim 1 , in which determining the account comprises:
 receiving an account identifier that identifies the account.   
     
     
       12. The method of  claim 1 , in which the timestamp comprises an account identifier that identifies the account. 
     
     
       13. The method of  claim 1 , in which the account is associated with the caller. 
     
     
       14. The method of  claim 1 , in which the account is associated with a third party. 
     
     
       15. The method of  claim 1 , in which determining the account comprises:
 determining the account based on the device identifier.   
     
     
       16. The method of  claim 1 , in which the account is a prepaid account. 
     
     
       17. The method of  claim 1 , in which charging the fee comprises:
 debiting the account based on the fee.   
     
     
       18. The method of  claim 1 , in which determining the representation of the time comprises:
 performing a cryptographic operation on the timestamp.   
     
     
       19. The method of  claim 1 , in which determining the representation of the time comprises:
 decrypting the timestamp based on the cryptographic key.   
     
     
       20. The method of  claim 1 , in which providing the representation of the time comprises:
 transmitting the representation of the time to the caller.   
     
     
       21. The method of  claim 1 , in which providing the representation of the time comprises:
 displaying the representation of the time to the caller.   
     
     
       22. The method of  claim 1 , in which determining the cryptographic key comprises:
 selecting a database record based on the device identifier, in which the database record comprises the device identifier.   
     
     
       23. A method comprising:
 receiving a sequence of DTMF signals from a caller via a telephone connection;   determining a timestamp based on the DTMF signals;   receiving a device identifier from the caller, in which the device identifier identifies a device;   determining a cryptographic key based on the device identifier;   determining a representation of a time based on the timestamp and the cryptographic key;   providing the representation of the time to the caller;   determining an account; and   charging a fee to the account.   
     
     
       24. A method comprising:
 receiving a timestamp from a timestamp recipient via an Internet connection;   receiving a device identifier via the Internet connection, in which the device identifier identifies a device;   determining a cryptographic key based on the device identifier;   determining a representation of a time based on the timestamp and the cryptographic key;   providing the representation of the time to the timestamp recipient via the Internet connection;   determining an account; and   charging a fee to the account.   
     
     
       25. A method, comprising:
 receiving, by a central controller, a timestamp from a timestamp recipient;   receiving, by the central controller, a device identifier that identifies a timestamp device;   utilizing, by the central controller, the device identifier to determine a cryptographic operation used to generate the timestamp;   attempting, by the central controller, to verify the timestamp by using the cryptographic operation on at least a portion of the timestamp;   communicating, by the central controller, the results of the attempt to verify to the timestamp recipient; and   charging a fee.   
     
     
       26. The method of claim 25, in which communicating the results of the attempt to verify comprises providing information concerning at least one of the integrity of the timestamp and the authenticity of the timestamp device. 
     
     
       27. The method of claim 25, in which charging a fee comprises determining an account and charging the fee to the account. 
     
     
       28. The method of claim 27, wherein the account comprises at least one of an account of the timestamp recipient, an account associated with a third party, and an account associated with the device identifier. 
     
     
       29. The method of claim 25, wherein the timestamp comprises a cleartext portion and a ciphertext portion. 
     
     
       30. The method of claim 29, wherein the ciphertext portion comprises a one-way function corresponding to at least one of a hash, a message authentication code, and a cyclic redundancy check. 
     
     
       31. The method of claim 25, wherein the timestamp is encrypted with a device private key. 
     
     
       32. The method of claim 31, in which attempting to verify further comprises decrypting the timestamp with a corresponding device public key. 
     
     
       33. The method of claim 32, wherein the device public key is provided by at least one of a public database and by use of a digital certificate within the timestamp. 
     
     
       34. The method of claim 25, wherein the timestamp is encrypted with a symmetric key. 
     
     
       35. A computer readable memory storing instructions configured to direct a processor to:
 receive a timestamp from a timestamp recipient;   receive a device identifier that identifies a timestamp device;   utilize the device identifier to determine a cryptographic operation used to generate the timestamp;   attempt to verify the timestamp by using the cryptographic operation on at least a portion of the timestamp;   communicate the results of the attempt to verify to the timestamp recipient; and   charge a fee.   
     
     
       36. The computer readable memory of claim 35, wherein the instructions to communicate the results of the attempt to verify direct the processor to provide information concerning at least one of the integrity of the timestamp and the authenticity of the timestamp device. 
     
     
       37. The computer readable memory of claim 36, wherein the instructions to charge a fee direct the processor to determine an account and charge the fee to the account. 
     
     
       38. An apparatus, comprising:
 a computer processor configured to receive a timestamp from a timestamp recipient and to receive a device identifier that identifies a timestamp device;   a memory in communication with the computer processor and storing a program for directing the computer processor to utilize the device identifier to determine a cryptographic operation used to generate the timestamp, and to attempt to verify the timestamp by using the cryptographic operation on at least a portion of the timestamp; and   an output device, controlled by the computer processor, for communicating the results of the attempt to verify to the timestamp recipient, and for outputting a charge for a fee.   
     
     
       39. A method, comprising:
 receiving, by a central controller, a timestamp from a timestamp recipient that includes a cleartext portion and a ciphertext portion;   receiving, by the central controller, a device identifier that identifies a timestamp device;   utilizing, by the central controller, the device identifier to determine a cryptographic key;   attempting, by the central controller, to verify the timestamp by using a cryptographic operation on the timestamp, wherein the cryptographic operation is associated with the cryptographic key;   communicating, by the central controller, the results of the attempt to verify to the timestamp recipient; and   charging a fee.   
     
     
       40. The method of claim 39, wherein the ciphertext portion comprises a one-way function corresponding to at least one of a hash, a message authentication code, and a cyclic redundancy check. 
     
     
       41. The method of claim 39, wherein the attempt to verify comprises:
 utilizing the cryptographic operation to decrypt the ciphertext portion of the timestamp;   comparing the decrypted ciphertext portion to the cleartext portion; and   verifying the timestamp if the decrypted ciphertext portion matches the cleartext portion.   
     
     
       42. The method of claim 41, wherein the timestamp is encrypted with a device private key, and the cryptographic operation comprises using a corresponding device public key. 
     
     
       43. The method of claim 42, wherein the device public key is provided by at least one of a public database and by use of a digital certificate within the timestamp. 
     
     
       44. The method of claim 39, wherein the ciphertext portion is a hash of a time representation produced by a chronographic device. 
     
     
       45. The method of claim 44, wherein the attempt to verify comprises:
 utilizing the cryptographic operation to compute a hash of the cleartext portion;   comparing the computed hash of the cleartext portion to the ciphertext portion; and   verifying the timestamp if the computed hash of the cleartext portion matches the ciphertext portion.   
     
     
       46. A computer readable memory storing instructions configured to direct a processor to:
 receive a timestamp from a timestamp recipient that includes a cleartext portion and a ciphertext portion;   receive a device identifier that identifies a timestamp device;   utilize the device identifier to determine a cryptographic key;   attempt to verify the timestamp by using a cryptographic operation on the timestamp, wherein the cryptographic operation is associated with the cryptographic key;   communicate the results of the attempt to verify to the timestamp recipient; and   charge a fee.   
     
     
       47. The computer readable memory of claim 46, wherein the instructions to attempt to verify the timestamp direct the processor to:
 utilize the cryptographic operation to decrypt the ciphertext portion of the timestamp;   compare the decrypted ciphertext portion to the cleartext portion; and   verify the timestamp if the decrypted ciphertext portion matches the cleartext portion.   
     
     
       48. The computer readable memory of claim 46, wherein the instructions to attempt to verify the timestamp direct the processor to:
 utilize the cryptographic operation to compute a hash of the cleartext portion;   compare the computed hash of the cleartext portion to the ciphertext portion; and   verify the timestamp if the computed hash of the cleartext portion matches the ciphertext portion.   
     
     
       49. An apparatus, comprising:
 a computer processor configured to receive a timestamp from a timestamp recipient that includes a cleartext portion and a ciphertext portion and to receive a device identifier that identifies a timestamp device;   a memory in communication with the computer processor and storing a program for directing the computer processor to utilize the device identifier to determine a cryptographic key, and to attempt to verify the timestamp by using a cryptographic operation on the timestamp, wherein the cryptographic operation is associated with the cryptographic key; and   an output device, controlled by the computer processor, for communicating the results of the attempt to verify to the timestamp recipient, and for outputting a charge for a fee.