US 7,411,868 B2Granted

Estimation of time within untrusted time device disconnected from trusted time device

AssigneeInternational Business Machines Corporation

InventorHisayuki Kohmoto

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Abstract

Upon connecting to a trusted device, an untrusted device: (a) acquires a trusted current time; (b) stores an elapsed time; (c) determines an estimated current time; and, (d) stores a time difference between the estimated current time and an untrusted current time. The untrusted device (e) repeats (b)-(d) until turned off. Upon being turned on and able to connect to the trusted device, the untrusted device (f) repeats (a)-(e). Otherwise, it: (g) determines a temporary current time; and, (h) compares the estimated current time of (c) with the temporary current time. The untrusted device, (i) where the estimated current time of (c) is less than the temporary current time, sets an offline current time as the temporary current time, or, (j) where the estimated current time of (c) is greater than the temporary current time, sets the offline current time as the estimated current time of (c).

Claims20

Dependent claims

A method performable by an untrusted time device comprising:

upon communicatively connecting to a trusted time device,
(a) acquiring a trusted current time from the trusted time device;
(b) storing an elapsed time, elapsed from the trusted current time;
(c) determining an estimated current time based on the trusted current time and the elapsed time;
(d) storing a time difference between the estimated current time and an untrusted current time of the untrusted time device;
(e) repeating (b)-(d) until the untrusted time device has been turned off;
upon the untrusted time device being turned on again,
where the untrusted time device is able to communicatively connect to the trusted time device, (f) repeating (a)-(e);
where the untrusted time device is unable to communicatively connect to the trusted time device,
(g) determining a temporary current time based on the time difference last stored in (d) and the untrusted current time of the untrusted time device;
(h) comparing the estimated current time last determined in (c) with the temporary current time;
(i) where the estimated current time last determined in (c) is less than the temporary current time, setting an offline current time equal to the temporary current time;
and,
(j) where the estimated current time last determined in (c) is greater than the temporary current time, setting the offline current time equal to the estimated current time last determined in (c).

11 more elements

A system comprising:

a network;
a trusted time device communicatively connectable to the network and providing a trusted current time;
and,
an untrusted time device communicatively connectable to the network and providing an untrusted current time,
wherein when the untrusted time device is communicatively coupled to the network, the untrusted time device utilizes as an online current time the trusted current time from the trusted time device plus an elapsed time, and maintains a time difference between the online current time and the untrusted current time, and
wherein when the untrusted time device is not communicatively coupled to the network,
the untrusted time device utilizes as an offline current time the untrusted current time plus the time difference last maintained where the online current time last utilized is less than the untrusted current time plus the time difference last maintained, and
the untrusted time device utilizes as the offline current time the online current time last utilized where the online current time last utilized is greater than the untrusted current time plus the time difference last maintained.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/991,161Filed 14 Nov 2004
Published: US 2006/0107042 A118 May 2006
Granted: 12 Aug 2008
Term ends: Not estimatedThe source records don’t support an estimate.

Classification3 codes

G06F 21/10
Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity: protecting distributed…
G06F 21/725
In cryptographic circuits: operating on a secure reference time value
G06F
Computing and data processing

Family

US 2006/0107042 A1Pre-grant publication · published 18 May 2006
US 7,411,868 B2This patent

From the US filing history. Foreign family members aren’t listed.

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