RTC Time Adjustment for Oscillator Drift in OTP Tokens
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Solution Overview
Problem
Imperfections in crystal oscillators within authentication tokens lead to time accuracy drift, necessitating wider OTP validity windows, which compromises authentication security by requiring more OTPs to be considered valid over a broader time range.
Innovation Solution
Implementing a method that uses a real-time clock circuit with self-contained time corrections, adjusting for oscillator imperfections by generating an adjustment factor to provide a new time value that accurately represents current time, allowing authentication tokens to resynchronize regularly and reducing the need for extensive OTP time window widening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the authentication entity widens the time period for valid OTPs to account for crystal oscillator imperfections, then time accuracy drift is compensated, but authentication security is lowered
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing compensation values in the authentication token based on measured crystal oscillator drift characteristics. During authentication, these pre-computed compensation values are used to adjust the time window, eliminating the need for the authentication entity to widen the time period and thereby maintaining security while compensating for drift.
Solution Approach 2:
The patent changes the parameter of time window calculation dynamically based on the specific drift characteristics of each token's crystal oscillator. Instead of using a fixed widened window, the system adjusts the time window parameter according to pre-measured drift rates, achieving precise compensation without excessive security degradation.
2Adaptability or versatility
If the authentication entity considers multiple OTPs as valid over a wider time range, then crystal oscillator drift is accommodated, but the number of valid OTPs increases
Solution Approach 1:
The system performs preliminary measurement of crystal oscillator drift characteristics during token manufacturing and stores compensation values in advance. This allows the authentication entity to use precise, token-specific time window calculations rather than broadly accommodating all possible drift scenarios, thereby limiting the number of valid OTPs to only those necessary for actual drift compensation.
3Duration of action of stationary object
If the authentication token lifetime is extended to multiple years, then device durability is improved, but time drift accumulates
Solution Approach 1:
The patent applies preliminary action by measuring and characterizing crystal oscillator drift during the manufacturing process, before the token enters service. The measured drift characteristics are stored as compensation values that remain valid throughout the token's multi-year lifetime, allowing long-term operation without requiring time synchronization updates while maintaining accurate time tracking.
Solution Approach 2:
The system changes the approach from continuous time synchronization to using fixed compensation parameters determined at manufacturing. This allows the token to operate accurately for years without external time references, as the compensation values account for the cumulative drift over the entire device lifetime.
Data Source
AI summary
A technique involves the use of an electronic device having a real-time clock (RTC) circuit. In particular, the technique involves obtaining an RTC value from the RTC circuit. The RTC value is based on a previous time value and being arranged to represent current time. The technique further involves generating an adjustment factor arranged to adjust for imperfection in an oscillator of the RTC circuit, and providing a new time value based on the RTC value and the adjustment factor. The new time value represents current time at least as accurately as the RTC value.