Method and apparatus for time calibration
AssigneesFujitsu Limited, Citizen Holdings Co., Ltd.
InventorsRyota Akiyama, Takeaki Kawashima
Life of this patent
Estimating the term…
Abstract
A local time is modified according to a radio wave time received from a time calibration signal transmitting station, as well as corrected according to an authentic time that is received from a time server when the difference between the local time and the radio wave time is less than a predetermined value as well as when the difference is equal to or greater than the predetermined value for a predetermined number of successive times. The local time is corrected while taking into consideration a delay period included in receiving the authentic time.
Claims15
A time-stamping device that affixes a digital signature including a local time clocked by an internal clock to electronic data, the time-stamping device comprising:
- a radio-transmitted-time receiving unit that receives a standard time included in a radio wave as a radio-transmitted time;
- an authentic-time receiving unit that receives an authentic time synchronized with the standard time from a time server;
- a calculating unit that calculates an absolute value of a difference between the radio-transmitted time and the local time;
- a time modifying unit that modifies, when the absolute value calculated is less than a first threshold value, the local time by setting the radio-transmitted time as the local time, and leaves, when the absolute value calculated is equal to or greater than the first threshold value, the local time as it is;
- and
- a time correcting unit that corrects the local time based on the authentic time received;
- wherein the authentic-time receiving unit receives the authentic time from the time server when the absolute value calculated is less than the first threshold value a predetermined number of successive times.
A time-stamping device that affixes a digital signature including a local time clocked by an internal clock to electronic data, the time-stamping device comprising:
- a radio-transmitted-time receiving unit that receives a standard time included in a radio wave as a radio-transmitted time;
- an authentic-time receiving unit that receives an authentic time synchronized with the standard time from a time server;
- a calculating unit that calculates an absolute value of a difference between the radio-transmitted time and the local time;
- a time modifying unit that modifies, when the absolute value calculated is less than a first threshold value, the local time by setting the radio-transmitted time as the local time, and leaves, when the absolute value calculated is equal to or greater than the first threshold value, the local time as it is;
- and
- a time correcting unit that corrects the local time based on the authentic time received;
- wherein the authentic-time receiving unit receives the authentic time from the time server when the absolute value calculated is equal to or greater than the first threshold value a predetermined number of successive times.
A time-stamping device that affixes a digital signature including a local time clocked by an internal clock to electronic data, the time-stamping device comprising:
- a radio-transmitted-time receiving unit that receives a standard time included in a radio wave as a radio-transmitted time;
- an authentic-time receiving unit that receives an authentic time synchronized with the standard time from a time server;
- a calculating unit that calculates an absolute value of a difference between the radio-transmitted time and the local time;
- a time modifying unit that modifies, when the absolute value calculated is less than a first threshold value, the local time by setting the radio-transmitted time as the local time, and leaves, when the absolute value calculated is equal to or greater than the first threshold value, the local time as it is;
- and
- a time correcting unit that corrects the local time based on the authentic time received;
- wherein the authentic-time receiving unit receives the authentic time from the time server when a predetermined operation is carried out.
A time-stamping device that affixes a digital signature including a local time clocked by an internal clock to electronic data, the time-stamping device comprising:
- a radio-transmitted-time receiving unit that receives a standard time included in a radio wave as a radio-transmitted time;
- an authentic-time receiving unit that receives an authentic time synchronized with the standard time from a time server;
- a calculating unit that calculates an absolute value of a difference between the radio-transmitted time and the local time;
- a time modifying unit that modifies, when the absolute value calculated is less than a first threshold value, the local time by setting the radio-transmitted time as the local time, and leaves, when the absolute value calculated is equal to or greater than the first threshold value, the local time as it is;
- and
- a time correcting unit that corrects the local time based on the authentic time received;
- wherein the time correcting unit corrects the local time by setting the authentic time received as the local time when the absolute value is less than a second threshold value.
A time-stamping device that affixes a digital signature including a local time clocked by an internal clock to electronic data, the time-stamping device comprising:
- a radio-transmitted-time receiving unit that receives a standard time included in a radio wave as a radio-transmitted time;
- an authentic-time receiving unit that receives an authentic time synchronized with the standard time from a time server;
- a calculating unit that calculates an absolute value of a difference between the radio-transmitted time and the local time;
- a time modifying unit that modifies, when the absolute value calculated is less than a first threshold value, the local time by setting the radio-transmitted time as the local time, and leaves, when the absolute value calculated is equal to or greater than the first threshold value, the local time as it is;
- and
- a time correcting unit that corrects the local time based on the authentic time received;
- wherein the time correcting unit suspends affixing the digital signature to electronic data and outputs an alert when the absolute value is equal to or greater than a second threshold value a predetermined number of successive times.
A time-stamping device that affixes a digital signature including a local time clocked by an internal clock to electronic data, the time-stamping device comprising:
- a radio-transmitted-time receiving unit that receives a standard time included in a radio wave as a radio-transmitted time;
- an authentic-time receiving unit that receives an authentic time synchronized with the standard time from a time server;
- a calculating unit that calculates an absolute value of a difference between the radio-transmitted time and the local time;
- a time modifying unit that modifies, when the absolute value calculated is less than a first threshold value, the local time by setting the radio-transmitted time as the local time, and leaves, when the absolute value calculated is equal to or greater than the first threshold value, the local time as it is;
- and
- a time correcting unit that corrects the local time based on the authentic time received;
- wherein the authentic-time receiving unit receives the authentic time when a value obtained by halving a delay period between making a request for the authentic time to the time server and receiving the authentic time from the time server is less than a second threshold value.
A time server for providing an authentic time for a time-stamping device that affixes a digital signature including a local time clocked by an internal clock to electronic data comprising:
- a receiving unit that receives a local time signed with a digital signature of a client from the client;
- a calculating unit that calculates an absolute value of a difference between the local time received and a reception time of the local time;
- and
- a sending unit that sends the local time received and the authentic time to the client when the absolute value calculated is less than a threshold value, wherein
- the authentic time is the reception time signed with a digital signature of the time server;
- and
- the sending unit sends an alert signed with the digital signature of the time server to the time-stamping device when the absolute value calculated is equal to or greater than the threshold value.
A method for correcting a difference between a local time clocked by an internal clock and a standard time, the method comprising:
- receiving a standard time included in a radio wave as a radio-transmitted time;
- receiving an authentic time synchronized with the standard time from a time server;
- calculating an absolute value of a difference between the radio-transmitted time and the local time;
- modifying the local time by setting the radio-transmitted time as the local time when the absolute value calculated is less than a threshold value;
- and
- correcting the local time based on the authentic time received;
- wherein the receiving includes receiving the authentic time from the time server when the absolute value calculated is less than the threshold value a predetermined number of successive times.
A method for correcting a difference between a local time clocked by an internal clock and a standard time, the method comprising:
- receiving a standard time included in a radio wave as a radio-transmitted time;
- receiving an authentic time synchronized with the standard time from a time server;
- calculating an absolute value of a difference between the radio-transmitted time and the local time;
- modifying the local time by setting the radio-transmitted time as the local time when the absolute value calculated is less than a threshold value;
- and
- correcting the local time based on the authentic time received;
- wherein the receiving includes receiving the authentic time from the time server when the absolute value calculated is equal to or greater than the threshold value a predetermined number of successive times.
A computer-readable recording medium that stores a computer program for correcting a difference between a local time clocked by an internal clock and a standard time, wherein the computer program causes a computer to execute:
- receiving a standard time included in a radio wave as a radio-transmitted time;
- receiving an authentic time synchronized with the standard time from a time server;
- calculating an absolute value of a difference between the radio-transmitted time and the local time;
- modifying the local time by setting the radio-transmitted time as the local time when the absolute value calculated is less than a threshold value;
- and
- correcting the local time based on the authentic time received;
- wherein the receiving includes receiving the authentic time from the time server when the absolute value calculated is less than the threshold value a predetermined number of successive times.
A computer-readable recording medium that stores a computer program for correcting a difference between a local time clocked by an internal clock and a standard time, wherein the computer program causes a computer to execute:
- receiving a standard time included in a radio wave as a radio-transmitted time;
- receiving an authentic time synchronized with the standard time from a time server;
- calculating an absolute value of a difference between the radio-transmitted time and the local time;
- modifying the local time by setting the radio-transmitted time as the local time when the absolute value calculated is less than a threshold value;
- and
- correcting the local time based on the authentic time received;
- wherein the receiving includes receiving the authentic time from the time server when the absolute value calculated is equal to or greater than the threshold value a predetermined number of successive times.
Dependencies are inferred from the claim text.